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linux/kernel/sched.c
Linus Torvalds fa490cfd15 Fix possible runqueue lock starvation in wait_task_inactive() 
Miklos Szeredi reported very long pauses (several seconds, sometimes
more) on his T60 (with a Core2Duo) which he managed to track down to
wait_task_inactive()'s open-coded busy-loop.

He observed that an interrupt on one core tries to acquire the
runqueue-lock but does not succeed in doing so for a very long time -
while wait_task_inactive() on the other core loops waiting for the first
core to deschedule a task (which it wont do while spinning in an
interrupt handler).

This rewrites wait_task_inactive() to do all its waiting optimistically
without any locks taken at all, and then just double-check the end
result with the proper runqueue lock held over just a very short
section.  If there were races in the optimistic wait, of a preemption
event scheduled the process away, we simply re-synchronize, and start
over.

So the code now looks like this:

	repeat:
		/* Unlocked, optimistic looping! */
		rq = task_rq(p);
		while (task_running(rq, p))
			cpu_relax();

		/* Get the *real* values */
		rq = task_rq_lock(p, &flags);
		running = task_running(rq, p);
		array = p->array;
		task_rq_unlock(rq, &flags);

		/* Check them.. */
		if (unlikely(running)) {
			cpu_relax();
			goto repeat;
		}

		/* Preempted away? Yield if so.. */
		if (unlikely(array)) {
			yield();
			goto repeat;
		}

Basically, that first "while()" loop is done entirely without any
locking at all (and doesn't check for the case where the target process
might have been preempted away), and so it's possibly "incorrect", but
we don't really care.  Both the runqueue used, and the "task_running()"
check might be the wrong tests, but they won't oops - they just mean
that we could possibly get the wrong results due to lack of locking and
exit the loop early in the case of a race condition.

So once we've exited the loop, we then get the proper (and careful) rq
lock, and check the running/runnable state _safely_.  And if it turns
out that our quick-and-dirty and unsafe loop was wrong after all, we
just go back and try it all again.

(The patch also adds a lot of comments, which is the actual bulk of it
all, to make it more obvious why we can do these things without holding
the locks).

Thanks to Miklos for all the testing and tracking it down.

Tested-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-06-18 11:52:55 -07:00

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/*
* kernel/sched.c
*
* Kernel scheduler and related syscalls
*
* Copyright (C) 1991-2002 Linus Torvalds
*
* 1996-12-23 Modified by Dave Grothe to fix bugs in semaphores and
* make semaphores SMP safe
* 1998-11-19 Implemented schedule_timeout() and related stuff
* by Andrea Arcangeli
* 2002-01-04 New ultra-scalable O(1) scheduler by Ingo Molnar:
* hybrid priority-list and round-robin design with
* an array-switch method of distributing timeslices
* and per-CPU runqueues. Cleanups and useful suggestions
* by Davide Libenzi, preemptible kernel bits by Robert Love.
* 2003-09-03 Interactivity tuning by Con Kolivas.
* 2004-04-02 Scheduler domains code by Nick Piggin
*/
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/nmi.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <linux/highmem.h>
#include <linux/smp_lock.h>
#include <asm/mmu_context.h>
#include <linux/interrupt.h>
#include <linux/capability.h>
#include <linux/completion.h>
#include <linux/kernel_stat.h>
#include <linux/debug_locks.h>
#include <linux/security.h>
#include <linux/notifier.h>
#include <linux/profile.h>
#include <linux/freezer.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/timer.h>
#include <linux/rcupdate.h>
#include <linux/cpu.h>
#include <linux/cpuset.h>
#include <linux/percpu.h>
#include <linux/kthread.h>
#include <linux/seq_file.h>
#include <linux/syscalls.h>
#include <linux/times.h>
#include <linux/tsacct_kern.h>
#include <linux/kprobes.h>
#include <linux/delayacct.h>
#include <linux/reciprocal_div.h>
#include <asm/tlb.h>
#include <asm/unistd.h>
/*
* Scheduler clock - returns current time in nanosec units.
* This is default implementation.
* Architectures and sub-architectures can override this.
*/
unsigned long long __attribute__((weak)) sched_clock(void)
{
return (unsigned long long)jiffies * (1000000000 / HZ);
}
/*
* Convert user-nice values [ -20 ... 0 ... 19 ]
* to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
* and back.
*/
#define NICE_TO_PRIO(nice) (MAX_RT_PRIO + (nice) + 20)
#define PRIO_TO_NICE(prio) ((prio) - MAX_RT_PRIO - 20)
#define TASK_NICE(p) PRIO_TO_NICE((p)->static_prio)
/*
* 'User priority' is the nice value converted to something we
* can work with better when scaling various scheduler parameters,
* it's a [ 0 ... 39 ] range.
*/
#define USER_PRIO(p) ((p)-MAX_RT_PRIO)
#define TASK_USER_PRIO(p) USER_PRIO((p)->static_prio)
#define MAX_USER_PRIO (USER_PRIO(MAX_PRIO))
/*
* Some helpers for converting nanosecond timing to jiffy resolution
*/
#define NS_TO_JIFFIES(TIME) ((TIME) / (1000000000 / HZ))
#define JIFFIES_TO_NS(TIME) ((TIME) * (1000000000 / HZ))
/*
* These are the 'tuning knobs' of the scheduler:
*
* Minimum timeslice is 5 msecs (or 1 jiffy, whichever is larger),
* default timeslice is 100 msecs, maximum timeslice is 800 msecs.
* Timeslices get refilled after they expire.
*/
#define MIN_TIMESLICE max(5 * HZ / 1000, 1)
#define DEF_TIMESLICE (100 * HZ / 1000)
#define ON_RUNQUEUE_WEIGHT 30
#define CHILD_PENALTY 95
#define PARENT_PENALTY 100
#define EXIT_WEIGHT 3
#define PRIO_BONUS_RATIO 25
#define MAX_BONUS (MAX_USER_PRIO * PRIO_BONUS_RATIO / 100)
#define INTERACTIVE_DELTA 2
#define MAX_SLEEP_AVG (DEF_TIMESLICE * MAX_BONUS)
#define STARVATION_LIMIT (MAX_SLEEP_AVG)
#define NS_MAX_SLEEP_AVG (JIFFIES_TO_NS(MAX_SLEEP_AVG))
/*
* If a task is 'interactive' then we reinsert it in the active
* array after it has expired its current timeslice. (it will not
* continue to run immediately, it will still roundrobin with
* other interactive tasks.)
*
* This part scales the interactivity limit depending on niceness.
*
* We scale it linearly, offset by the INTERACTIVE_DELTA delta.
* Here are a few examples of different nice levels:
*
* TASK_INTERACTIVE(-20): [1,1,1,1,1,1,1,1,1,0,0]
* TASK_INTERACTIVE(-10): [1,1,1,1,1,1,1,0,0,0,0]
* TASK_INTERACTIVE( 0): [1,1,1,1,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 10): [1,1,0,0,0,0,0,0,0,0,0]
* TASK_INTERACTIVE( 19): [0,0,0,0,0,0,0,0,0,0,0]
*
* (the X axis represents the possible -5 ... 0 ... +5 dynamic
* priority range a task can explore, a value of '1' means the
* task is rated interactive.)
*
* Ie. nice +19 tasks can never get 'interactive' enough to be
* reinserted into the active array. And only heavily CPU-hog nice -20
* tasks will be expired. Default nice 0 tasks are somewhere between,
* it takes some effort for them to get interactive, but it's not
* too hard.
*/
#define CURRENT_BONUS(p) \
(NS_TO_JIFFIES((p)->sleep_avg) * MAX_BONUS / \
MAX_SLEEP_AVG)
#define GRANULARITY (10 * HZ / 1000 ? : 1)
#ifdef CONFIG_SMP
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)) * \
num_online_cpus())
#else
#define TIMESLICE_GRANULARITY(p) (GRANULARITY * \
(1 << (((MAX_BONUS - CURRENT_BONUS(p)) ? : 1) - 1)))
#endif
#define SCALE(v1,v1_max,v2_max) \
(v1) * (v2_max) / (v1_max)
#define DELTA(p) \
(SCALE(TASK_NICE(p) + 20, 40, MAX_BONUS) - 20 * MAX_BONUS / 40 + \
INTERACTIVE_DELTA)
#define TASK_INTERACTIVE(p) \
((p)->prio <= (p)->static_prio - DELTA(p))
#define INTERACTIVE_SLEEP(p) \
(JIFFIES_TO_NS(MAX_SLEEP_AVG * \
(MAX_BONUS / 2 + DELTA((p)) + 1) / MAX_BONUS - 1))
#define TASK_PREEMPTS_CURR(p, rq) \
((p)->prio < (rq)->curr->prio)
#define SCALE_PRIO(x, prio) \
max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE)
static unsigned int static_prio_timeslice(int static_prio)
{
if (static_prio < NICE_TO_PRIO(0))
return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio);
else
return SCALE_PRIO(DEF_TIMESLICE, static_prio);
}
#ifdef CONFIG_SMP
/*
* Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
* Since cpu_power is a 'constant', we can use a reciprocal divide.
*/
static inline u32 sg_div_cpu_power(const struct sched_group *sg, u32 load)
{
return reciprocal_divide(load, sg->reciprocal_cpu_power);
}
/*
* Each time a sched group cpu_power is changed,
* we must compute its reciprocal value
*/
static inline void sg_inc_cpu_power(struct sched_group *sg, u32 val)
{
sg->__cpu_power += val;
sg->reciprocal_cpu_power = reciprocal_value(sg->__cpu_power);
}
#endif
/*
* task_timeslice() scales user-nice values [ -20 ... 0 ... 19 ]
* to time slice values: [800ms ... 100ms ... 5ms]
*
* The higher a thread's priority, the bigger timeslices
* it gets during one round of execution. But even the lowest
* priority thread gets MIN_TIMESLICE worth of execution time.
*/
static inline unsigned int task_timeslice(struct task_struct *p)
{
return static_prio_timeslice(p->static_prio);
}
/*
* These are the runqueue data structures:
*/
struct prio_array {
unsigned int nr_active;
DECLARE_BITMAP(bitmap, MAX_PRIO+1); /* include 1 bit for delimiter */
struct list_head queue[MAX_PRIO];
};
/*
* This is the main, per-CPU runqueue data structure.
*
* Locking rule: those places that want to lock multiple runqueues
* (such as the load balancing or the thread migration code), lock
* acquire operations must be ordered by ascending &runqueue.
*/
struct rq {
spinlock_t lock;
/*
* nr_running and cpu_load should be in the same cacheline because
* remote CPUs use both these fields when doing load calculation.
*/
unsigned long nr_running;
unsigned long raw_weighted_load;
#ifdef CONFIG_SMP
unsigned long cpu_load[3];
unsigned char idle_at_tick;
#ifdef CONFIG_NO_HZ
unsigned char in_nohz_recently;
#endif
#endif
unsigned long long nr_switches;
/*
* This is part of a global counter where only the total sum
* over all CPUs matters. A task can increase this counter on
* one CPU and if it got migrated afterwards it may decrease
* it on another CPU. Always updated under the runqueue lock:
*/
unsigned long nr_uninterruptible;
unsigned long expired_timestamp;
/* Cached timestamp set by update_cpu_clock() */
unsigned long long most_recent_timestamp;
struct task_struct *curr, *idle;
unsigned long next_balance;
struct mm_struct *prev_mm;
struct prio_array *active, *expired, arrays[2];
int best_expired_prio;
atomic_t nr_iowait;
#ifdef CONFIG_SMP
struct sched_domain *sd;
/* For active balancing */
int active_balance;
int push_cpu;
int cpu; /* cpu of this runqueue */
struct task_struct *migration_thread;
struct list_head migration_queue;
#endif
#ifdef CONFIG_SCHEDSTATS
/* latency stats */
struct sched_info rq_sched_info;
/* sys_sched_yield() stats */
unsigned long yld_exp_empty;
unsigned long yld_act_empty;
unsigned long yld_both_empty;
unsigned long yld_cnt;
/* schedule() stats */
unsigned long sched_switch;
unsigned long sched_cnt;
unsigned long sched_goidle;
/* try_to_wake_up() stats */
unsigned long ttwu_cnt;
unsigned long ttwu_local;
#endif
struct lock_class_key rq_lock_key;
};
static DEFINE_PER_CPU(struct rq, runqueues) ____cacheline_aligned_in_smp;
static DEFINE_MUTEX(sched_hotcpu_mutex);
static inline int cpu_of(struct rq *rq)
{
#ifdef CONFIG_SMP
return rq->cpu;
#else
return 0;
#endif
}
/*
* The domain tree (rq->sd) is protected by RCU's quiescent state transition.
* See detach_destroy_domains: synchronize_sched for details.
*
* The domain tree of any CPU may only be accessed from within
* preempt-disabled sections.
*/
#define for_each_domain(cpu, __sd) \
for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
#define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
#define this_rq() (&__get_cpu_var(runqueues))
#define task_rq(p) cpu_rq(task_cpu(p))
#define cpu_curr(cpu) (cpu_rq(cpu)->curr)
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
#endif
#ifndef finish_arch_switch
# define finish_arch_switch(prev) do { } while (0)
#endif
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
static inline int task_running(struct rq *rq, struct task_struct *p)
{
return rq->curr == p;
}
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq->lock.owner = current;
#endif
/*
* If we are tracking spinlock dependencies then we have to
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
spin_unlock_irq(&rq->lock);
}
#else /* __ARCH_WANT_UNLOCKED_CTXSW */
static inline int task_running(struct rq *rq, struct task_struct *p)
{
#ifdef CONFIG_SMP
return p->oncpu;
#else
return rq->curr == p;
#endif
}
static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
#ifdef CONFIG_SMP
/*
* We can optimise this out completely for !SMP, because the
* SMP rebalancing from interrupt is the only thing that cares
* here.
*/
next->oncpu = 1;
#endif
#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW
spin_unlock_irq(&rq->lock);
#else
spin_unlock(&rq->lock);
#endif
}
static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
{
#ifdef CONFIG_SMP
/*
* After ->oncpu is cleared, the task can be moved to a different CPU.
* We must ensure this doesn't happen until the switch is completely
* finished.
*/
smp_wmb();
prev->oncpu = 0;
#endif
#ifndef __ARCH_WANT_INTERRUPTS_ON_CTXSW
local_irq_enable();
#endif
}
#endif /* __ARCH_WANT_UNLOCKED_CTXSW */
/*
* __task_rq_lock - lock the runqueue a given task resides on.
* Must be called interrupts disabled.
*/
static inline struct rq *__task_rq_lock(struct task_struct *p)
__acquires(rq->lock)
{
struct rq *rq;
repeat_lock_task:
rq = task_rq(p);
spin_lock(&rq->lock);
if (unlikely(rq != task_rq(p))) {
spin_unlock(&rq->lock);
goto repeat_lock_task;
}
return rq;
}
/*
* task_rq_lock - lock the runqueue a given task resides on and disable
* interrupts. Note the ordering: we can safely lookup the task_rq without
* explicitly disabling preemption.
*/
static struct rq *task_rq_lock(struct task_struct *p, unsigned long *flags)
__acquires(rq->lock)
{
struct rq *rq;
repeat_lock_task:
local_irq_save(*flags);
rq = task_rq(p);
spin_lock(&rq->lock);
if (unlikely(rq != task_rq(p))) {
spin_unlock_irqrestore(&rq->lock, *flags);
goto repeat_lock_task;
}
return rq;
}
static inline void __task_rq_unlock(struct rq *rq)
__releases(rq->lock)
{
spin_unlock(&rq->lock);
}
static inline void task_rq_unlock(struct rq *rq, unsigned long *flags)
__releases(rq->lock)
{
spin_unlock_irqrestore(&rq->lock, *flags);
}
#ifdef CONFIG_SCHEDSTATS
/*
* bump this up when changing the output format or the meaning of an existing
* format, so that tools can adapt (or abort)
*/
#define SCHEDSTAT_VERSION 14
static int show_schedstat(struct seq_file *seq, void *v)
{
int cpu;
seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
seq_printf(seq, "timestamp %lu\n", jiffies);
for_each_online_cpu(cpu) {
struct rq *rq = cpu_rq(cpu);
#ifdef CONFIG_SMP
struct sched_domain *sd;
int dcnt = 0;
#endif
/* runqueue-specific stats */
seq_printf(seq,
"cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
cpu, rq->yld_both_empty,
rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt,
rq->sched_switch, rq->sched_cnt, rq->sched_goidle,
rq->ttwu_cnt, rq->ttwu_local,
rq->rq_sched_info.cpu_time,
rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt);
seq_printf(seq, "\n");
#ifdef CONFIG_SMP
/* domain-specific stats */
preempt_disable();
for_each_domain(cpu, sd) {
enum idle_type itype;
char mask_str[NR_CPUS];
cpumask_scnprintf(mask_str, NR_CPUS, sd->span);
seq_printf(seq, "domain%d %s", dcnt++, mask_str);
for (itype = SCHED_IDLE; itype < MAX_IDLE_TYPES;
itype++) {
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu "
"%lu",
sd->lb_cnt[itype],
sd->lb_balanced[itype],
sd->lb_failed[itype],
sd->lb_imbalance[itype],
sd->lb_gained[itype],
sd->lb_hot_gained[itype],
sd->lb_nobusyq[itype],
sd->lb_nobusyg[itype]);
}
seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu"
" %lu %lu %lu\n",
sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
sd->ttwu_wake_remote, sd->ttwu_move_affine,
sd->ttwu_move_balance);
}
preempt_enable();
#endif
}
return 0;
}
static int schedstat_open(struct inode *inode, struct file *file)
{
unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
char *buf = kmalloc(size, GFP_KERNEL);
struct seq_file *m;
int res;
if (!buf)
return -ENOMEM;
res = single_open(file, show_schedstat, NULL);
if (!res) {
m = file->private_data;
m->buf = buf;
m->size = size;
} else
kfree(buf);
return res;
}
const struct file_operations proc_schedstat_operations = {
.open = schedstat_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
/*
* Expects runqueue lock to be held for atomicity of update
*/
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{
if (rq) {
rq->rq_sched_info.run_delay += delta_jiffies;
rq->rq_sched_info.pcnt++;
}
}
/*
* Expects runqueue lock to be held for atomicity of update
*/
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{
if (rq)
rq->rq_sched_info.cpu_time += delta_jiffies;
}
# define schedstat_inc(rq, field) do { (rq)->field++; } while (0)
# define schedstat_add(rq, field, amt) do { (rq)->field += (amt); } while (0)
#else /* !CONFIG_SCHEDSTATS */
static inline void
rq_sched_info_arrive(struct rq *rq, unsigned long delta_jiffies)
{}
static inline void
rq_sched_info_depart(struct rq *rq, unsigned long delta_jiffies)
{}
# define schedstat_inc(rq, field) do { } while (0)
# define schedstat_add(rq, field, amt) do { } while (0)
#endif
/*
* this_rq_lock - lock this runqueue and disable interrupts.
*/
static inline struct rq *this_rq_lock(void)
__acquires(rq->lock)
{
struct rq *rq;
local_irq_disable();
rq = this_rq();
spin_lock(&rq->lock);
return rq;
}
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
/*
* Called when a process is dequeued from the active array and given
* the cpu. We should note that with the exception of interactive
* tasks, the expired queue will become the active queue after the active
* queue is empty, without explicitly dequeuing and requeuing tasks in the
* expired queue. (Interactive tasks may be requeued directly to the
* active queue, thus delaying tasks in the expired queue from running;
* see scheduler_tick()).
*
* This function is only called from sched_info_arrive(), rather than
* dequeue_task(). Even though a task may be queued and dequeued multiple
* times as it is shuffled about, we're really interested in knowing how
* long it was from the *first* time it was queued to the time that it
* finally hit a cpu.
*/
static inline void sched_info_dequeued(struct task_struct *t)
{
t->sched_info.last_queued = 0;
}
/*
* Called when a task finally hits the cpu. We can now calculate how
* long it was waiting to run. We also note when it began so that we
* can keep stats on how long its timeslice is.
*/
static void sched_info_arrive(struct task_struct *t)
{
unsigned long now = jiffies, delta_jiffies = 0;
if (t->sched_info.last_queued)
delta_jiffies = now - t->sched_info.last_queued;
sched_info_dequeued(t);
t->sched_info.run_delay += delta_jiffies;
t->sched_info.last_arrival = now;
t->sched_info.pcnt++;
rq_sched_info_arrive(task_rq(t), delta_jiffies);
}
/*
* Called when a process is queued into either the active or expired
* array. The time is noted and later used to determine how long we
* had to wait for us to reach the cpu. Since the expired queue will
* become the active queue after active queue is empty, without dequeuing
* and requeuing any tasks, we are interested in queuing to either. It
* is unusual but not impossible for tasks to be dequeued and immediately
* requeued in the same or another array: this can happen in sched_yield(),
* set_user_nice(), and even load_balance() as it moves tasks from runqueue
* to runqueue.
*
* This function is only called from enqueue_task(), but also only updates
* the timestamp if it is already not set. It's assumed that
* sched_info_dequeued() will clear that stamp when appropriate.
*/
static inline void sched_info_queued(struct task_struct *t)
{
if (unlikely(sched_info_on()))
if (!t->sched_info.last_queued)
t->sched_info.last_queued = jiffies;
}
/*
* Called when a process ceases being the active-running process, either
* voluntarily or involuntarily. Now we can calculate how long we ran.
*/
static inline void sched_info_depart(struct task_struct *t)
{
unsigned long delta_jiffies = jiffies - t->sched_info.last_arrival;
t->sched_info.cpu_time += delta_jiffies;
rq_sched_info_depart(task_rq(t), delta_jiffies);
}
/*
* Called when tasks are switched involuntarily due, typically, to expiring
* their time slice. (This may also be called when switching to or from
* the idle task.) We are only called when prev != next.
*/
static inline void
__sched_info_switch(struct task_struct *prev, struct task_struct *next)
{
struct rq *rq = task_rq(prev);
/*
* prev now departs the cpu. It's not interesting to record
* stats about how efficient we were at scheduling the idle
* process, however.
*/
if (prev != rq->idle)
sched_info_depart(prev);
if (next != rq->idle)
sched_info_arrive(next);
}
static inline void
sched_info_switch(struct task_struct *prev, struct task_struct *next)
{
if (unlikely(sched_info_on()))
__sched_info_switch(prev, next);
}
#else
#define sched_info_queued(t) do { } while (0)
#define sched_info_switch(t, next) do { } while (0)
#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */
/*
* Adding/removing a task to/from a priority array:
*/
static void dequeue_task(struct task_struct *p, struct prio_array *array)
{
array->nr_active--;
list_del(&p->run_list);
if (list_empty(array->queue + p->prio))
__clear_bit(p->prio, array->bitmap);
}
static void enqueue_task(struct task_struct *p, struct prio_array *array)
{
sched_info_queued(p);
list_add_tail(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* Put task to the end of the run list without the overhead of dequeue
* followed by enqueue.
*/
static void requeue_task(struct task_struct *p, struct prio_array *array)
{
list_move_tail(&p->run_list, array->queue + p->prio);
}
static inline void
enqueue_task_head(struct task_struct *p, struct prio_array *array)
{
list_add(&p->run_list, array->queue + p->prio);
__set_bit(p->prio, array->bitmap);
array->nr_active++;
p->array = array;
}
/*
* __normal_prio - return the priority that is based on the static
* priority but is modified by bonuses/penalties.
*
* We scale the actual sleep average [0 .... MAX_SLEEP_AVG]
* into the -5 ... 0 ... +5 bonus/penalty range.
*
* We use 25% of the full 0...39 priority range so that:
*
* 1) nice +19 interactive tasks do not preempt nice 0 CPU hogs.
* 2) nice -20 CPU hogs do not get preempted by nice 0 tasks.
*
* Both properties are important to certain workloads.
*/
static inline int __normal_prio(struct task_struct *p)
{
int bonus, prio;
bonus = CURRENT_BONUS(p) - MAX_BONUS / 2;
prio = p->static_prio - bonus;
if (prio < MAX_RT_PRIO)
prio = MAX_RT_PRIO;
if (prio > MAX_PRIO-1)
prio = MAX_PRIO-1;
return prio;
}
/*
* To aid in avoiding the subversion of "niceness" due to uneven distribution
* of tasks with abnormal "nice" values across CPUs the contribution that
* each task makes to its run queue's load is weighted according to its
* scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a
* scaled version of the new time slice allocation that they receive on time
* slice expiry etc.
*/
/*
* Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE
* If static_prio_timeslice() is ever changed to break this assumption then
* this code will need modification
*/
#define TIME_SLICE_NICE_ZERO DEF_TIMESLICE
#define LOAD_WEIGHT(lp) \
(((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO)
#define PRIO_TO_LOAD_WEIGHT(prio) \
LOAD_WEIGHT(static_prio_timeslice(prio))
#define RTPRIO_TO_LOAD_WEIGHT(rp) \
(PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp))
static void set_load_weight(struct task_struct *p)
{
if (has_rt_policy(p)) {
#ifdef CONFIG_SMP
if (p == task_rq(p)->migration_thread)
/*
* The migration thread does the actual balancing.
* Giving its load any weight will skew balancing
* adversely.
*/
p->load_weight = 0;
else
#endif
p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority);
} else
p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio);
}
static inline void
inc_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
rq->raw_weighted_load += p->load_weight;
}
static inline void
dec_raw_weighted_load(struct rq *rq, const struct task_struct *p)
{
rq->raw_weighted_load -= p->load_weight;
}
static inline void inc_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running++;
inc_raw_weighted_load(rq, p);
}
static inline void dec_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running--;
dec_raw_weighted_load(rq, p);
}
/*
* Calculate the expected normal priority: i.e. priority
* without taking RT-inheritance into account. Might be
* boosted by interactivity modifiers. Changes upon fork,
* setprio syscalls, and whenever the interactivity
* estimator recalculates.
*/
static inline int normal_prio(struct task_struct *p)
{
int prio;
if (has_rt_policy(p))
prio = MAX_RT_PRIO-1 - p->rt_priority;
else
prio = __normal_prio(p);
return prio;
}
/*
* Calculate the current priority, i.e. the priority
* taken into account by the scheduler. This value might
* be boosted by RT tasks, or might be boosted by
* interactivity modifiers. Will be RT if the task got
* RT-boosted. If not then it returns p->normal_prio.
*/
static int effective_prio(struct task_struct *p)
{
p->normal_prio = normal_prio(p);
/*
* If we are RT tasks or we were boosted to RT priority,
* keep the priority unchanged. Otherwise, update priority
* to the normal priority:
*/
if (!rt_prio(p->prio))
return p->normal_prio;
return p->prio;
}
/*
* __activate_task - move a task to the runqueue.
*/
static void __activate_task(struct task_struct *p, struct rq *rq)
{
struct prio_array *target = rq->active;
if (batch_task(p))
target = rq->expired;
enqueue_task(p, target);
inc_nr_running(p, rq);
}
/*
* __activate_idle_task - move idle task to the _front_ of runqueue.
*/
static inline void __activate_idle_task(struct task_struct *p, struct rq *rq)
{
enqueue_task_head(p, rq->active);
inc_nr_running(p, rq);
}
/*
* Recalculate p->normal_prio and p->prio after having slept,
* updating the sleep-average too:
*/
static int recalc_task_prio(struct task_struct *p, unsigned long long now)
{
/* Caller must always ensure 'now >= p->timestamp' */
unsigned long sleep_time = now - p->timestamp;
if (batch_task(p))
sleep_time = 0;
if (likely(sleep_time > 0)) {
/*
* This ceiling is set to the lowest priority that would allow
* a task to be reinserted into the active array on timeslice
* completion.
*/
unsigned long ceiling = INTERACTIVE_SLEEP(p);
if (p->mm && sleep_time > ceiling && p->sleep_avg < ceiling) {
/*
* Prevents user tasks from achieving best priority
* with one single large enough sleep.
*/
p->sleep_avg = ceiling;
/*
* Using INTERACTIVE_SLEEP() as a ceiling places a
* nice(0) task 1ms sleep away from promotion, and
* gives it 700ms to round-robin with no chance of
* being demoted. This is more than generous, so
* mark this sleep as non-interactive to prevent the
* on-runqueue bonus logic from intervening should
* this task not receive cpu immediately.
*/
p->sleep_type = SLEEP_NONINTERACTIVE;
} else {
/*
* Tasks waking from uninterruptible sleep are
* limited in their sleep_avg rise as they
* are likely to be waiting on I/O
*/
if (p->sleep_type == SLEEP_NONINTERACTIVE && p->mm) {
if (p->sleep_avg >= ceiling)
sleep_time = 0;
else if (p->sleep_avg + sleep_time >=
ceiling) {
p->sleep_avg = ceiling;
sleep_time = 0;
}
}
/*
* This code gives a bonus to interactive tasks.
*
* The boost works by updating the 'average sleep time'
* value here, based on ->timestamp. The more time a
* task spends sleeping, the higher the average gets -
* and the higher the priority boost gets as well.
*/
p->sleep_avg += sleep_time;
}
if (p->sleep_avg > NS_MAX_SLEEP_AVG)
p->sleep_avg = NS_MAX_SLEEP_AVG;
}
return effective_prio(p);
}
/*
* activate_task - move a task to the runqueue and do priority recalculation
*
* Update all the scheduling statistics stuff. (sleep average
* calculation, priority modifiers, etc.)
*/
static void activate_task(struct task_struct *p, struct rq *rq, int local)
{
unsigned long long now;
if (rt_task(p))
goto out;
now = sched_clock();
#ifdef CONFIG_SMP
if (!local) {
/* Compensate for drifting sched_clock */
struct rq *this_rq = this_rq();
now = (now - this_rq->most_recent_timestamp)
+ rq->most_recent_timestamp;
}
#endif
/*
* Sleep time is in units of nanosecs, so shift by 20 to get a
* milliseconds-range estimation of the amount of time that the task
* spent sleeping:
*/
if (unlikely(prof_on == SLEEP_PROFILING)) {
if (p->state == TASK_UNINTERRUPTIBLE)
profile_hits(SLEEP_PROFILING, (void *)get_wchan(p),
(now - p->timestamp) >> 20);
}
p->prio = recalc_task_prio(p, now);
/*
* This checks to make sure it's not an uninterruptible task
* that is now waking up.
*/
if (p->sleep_type == SLEEP_NORMAL) {
/*
* Tasks which were woken up by interrupts (ie. hw events)
* are most likely of interactive nature. So we give them
* the credit of extending their sleep time to the period
* of time they spend on the runqueue, waiting for execution
* on a CPU, first time around:
*/
if (in_interrupt())
p->sleep_type = SLEEP_INTERRUPTED;
else {
/*
* Normal first-time wakeups get a credit too for
* on-runqueue time, but it will be weighted down:
*/
p->sleep_type = SLEEP_INTERACTIVE;
}
}
p->timestamp = now;
out:
__activate_task(p, rq);
}
/*
* deactivate_task - remove a task from the runqueue.
*/
static void deactivate_task(struct task_struct *p, struct rq *rq)
{
dec_nr_running(p, rq);
dequeue_task(p, p->array);
p->array = NULL;
}
/*
* resched_task - mark a task 'to be rescheduled now'.
*
* On UP this means the setting of the need_resched flag, on SMP it
* might also involve a cross-CPU call to trigger the scheduler on
* the target CPU.
*/
#ifdef CONFIG_SMP
#ifndef tsk_is_polling
#define tsk_is_polling(t) test_tsk_thread_flag(t, TIF_POLLING_NRFLAG)
#endif
static void resched_task(struct task_struct *p)
{
int cpu;
assert_spin_locked(&task_rq(p)->lock);
if (unlikely(test_tsk_thread_flag(p, TIF_NEED_RESCHED)))
return;
set_tsk_thread_flag(p, TIF_NEED_RESCHED);
cpu = task_cpu(p);
if (cpu == smp_processor_id())
return;
/* NEED_RESCHED must be visible before we test polling */
smp_mb();
if (!tsk_is_polling(p))
smp_send_reschedule(cpu);
}
static void resched_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
if (!spin_trylock_irqsave(&rq->lock, flags))
return;
resched_task(cpu_curr(cpu));
spin_unlock_irqrestore(&rq->lock, flags);
}
#else
static inline void resched_task(struct task_struct *p)
{
assert_spin_locked(&task_rq(p)->lock);
set_tsk_need_resched(p);
}
#endif
/**
* task_curr - is this task currently executing on a CPU?
* @p: the task in question.
*/
inline int task_curr(const struct task_struct *p)
{
return cpu_curr(task_cpu(p)) == p;
}
/* Used instead of source_load when we know the type == 0 */
unsigned long weighted_cpuload(const int cpu)
{
return cpu_rq(cpu)->raw_weighted_load;
}
#ifdef CONFIG_SMP
struct migration_req {
struct list_head list;
struct task_struct *task;
int dest_cpu;
struct completion done;
};
/*
* The task's runqueue lock must be held.
* Returns true if you have to wait for migration thread.
*/
static int
migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req)
{
struct rq *rq = task_rq(p);
/*
* If the task is not on a runqueue (and not running), then
* it is sufficient to simply update the task's cpu field.
*/
if (!p->array && !task_running(rq, p)) {
set_task_cpu(p, dest_cpu);
return 0;
}
init_completion(&req->done);
req->task = p;
req->dest_cpu = dest_cpu;
list_add(&req->list, &rq->migration_queue);
return 1;
}
/*
* wait_task_inactive - wait for a thread to unschedule.
*
* The caller must ensure that the task *will* unschedule sometime soon,
* else this function might spin for a *long* time. This function can't
* be called with interrupts off, or it may introduce deadlock with
* smp_call_function() if an IPI is sent by the same process we are
* waiting to become inactive.
*/
void wait_task_inactive(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
struct prio_array *array;
int running;
repeat:
/*
* We do the initial early heuristics without holding
* any task-queue locks at all. We'll only try to get
* the runqueue lock when things look like they will
* work out!
*/
rq = task_rq(p);
/*
* If the task is actively running on another CPU
* still, just relax and busy-wait without holding
* any locks.
*
* NOTE! Since we don't hold any locks, it's not
* even sure that "rq" stays as the right runqueue!
* But we don't care, since "task_running()" will
* return false if the runqueue has changed and p
* is actually now running somewhere else!
*/
while (task_running(rq, p))
cpu_relax();
/*
* Ok, time to look more closely! We need the rq
* lock now, to be *sure*. If we're wrong, we'll
* just go back and repeat.
*/
rq = task_rq_lock(p, &flags);
running = task_running(rq, p);
array = p->array;
task_rq_unlock(rq, &flags);
/*
* Was it really running after all now that we
* checked with the proper locks actually held?
*
* Oops. Go back and try again..
*/
if (unlikely(running)) {
cpu_relax();
goto repeat;
}
/*
* It's not enough that it's not actively running,
* it must be off the runqueue _entirely_, and not
* preempted!
*
* So if it wa still runnable (but just not actively
* running right now), it's preempted, and we should
* yield - it could be a while.
*/
if (unlikely(array)) {
yield();
goto repeat;
}
/*
* Ahh, all good. It wasn't running, and it wasn't
* runnable, which means that it will never become
* running in the future either. We're all done!
*/
}
/***
* kick_process - kick a running thread to enter/exit the kernel
* @p: the to-be-kicked thread
*
* Cause a process which is running on another CPU to enter
* kernel-mode, without any delay. (to get signals handled.)
*
* NOTE: this function doesnt have to take the runqueue lock,
* because all it wants to ensure is that the remote task enters
* the kernel. If the IPI races and the task has been migrated
* to another CPU then no harm is done and the purpose has been
* achieved as well.
*/
void kick_process(struct task_struct *p)
{
int cpu;
preempt_disable();
cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
smp_send_reschedule(cpu);
preempt_enable();
}
/*
* Return a low guess at the load of a migration-source cpu weighted
* according to the scheduling class and "nice" value.
*
* We want to under-estimate the load of migration sources, to
* balance conservatively.
*/
static inline unsigned long source_load(int cpu, int type)
{
struct rq *rq = cpu_rq(cpu);
if (type == 0)
return rq->raw_weighted_load;
return min(rq->cpu_load[type-1], rq->raw_weighted_load);
}
/*
* Return a high guess at the load of a migration-target cpu weighted
* according to the scheduling class and "nice" value.
*/
static inline unsigned long target_load(int cpu, int type)
{
struct rq *rq = cpu_rq(cpu);
if (type == 0)
return rq->raw_weighted_load;
return max(rq->cpu_load[type-1], rq->raw_weighted_load);
}
/*
* Return the average load per task on the cpu's run queue
*/
static inline unsigned long cpu_avg_load_per_task(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long n = rq->nr_running;
return n ? rq->raw_weighted_load / n : SCHED_LOAD_SCALE;
}
/*
* find_idlest_group finds and returns the least busy CPU group within the
* domain.
*/
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
{
struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
unsigned long min_load = ULONG_MAX, this_load = 0;
int load_idx = sd->forkexec_idx;
int imbalance = 100 + (sd->imbalance_pct-100)/2;
do {
unsigned long load, avg_load;
int local_group;
int i;
/* Skip over this group if it has no CPUs allowed */
if (!cpus_intersects(group->cpumask, p->cpus_allowed))
goto nextgroup;
local_group = cpu_isset(this_cpu, group->cpumask);
/* Tally up the load of all CPUs in the group */
avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
/* Bias balancing toward cpus of our domain */
if (local_group)
load = source_load(i, load_idx);
else
load = target_load(i, load_idx);
avg_load += load;
}
/* Adjust by relative CPU power of the group */
avg_load = sg_div_cpu_power(group,
avg_load * SCHED_LOAD_SCALE);
if (local_group) {
this_load = avg_load;
this = group;
} else if (avg_load < min_load) {
min_load = avg_load;
idlest = group;
}
nextgroup:
group = group->next;
} while (group != sd->groups);
if (!idlest || 100*this_load < imbalance*min_load)
return NULL;
return idlest;
}
/*
* find_idlest_cpu - find the idlest cpu among the cpus in group.
*/
static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
cpumask_t tmp;
unsigned long load, min_load = ULONG_MAX;
int idlest = -1;
int i;
/* Traverse only the allowed CPUs */
cpus_and(tmp, group->cpumask, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
load = weighted_cpuload(i);
if (load < min_load || (load == min_load && i == this_cpu)) {
min_load = load;
idlest = i;
}
}
return idlest;
}
/*
* sched_balance_self: balance the current task (running on cpu) in domains
* that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
* SD_BALANCE_EXEC.
*
* Balance, ie. select the least loaded group.
*
* Returns the target CPU number, or the same CPU if no balancing is needed.
*
* preempt must be disabled.
*/
static int sched_balance_self(int cpu, int flag)
{
struct task_struct *t = current;
struct sched_domain *tmp, *sd = NULL;
for_each_domain(cpu, tmp) {
/*
* If power savings logic is enabled for a domain, stop there.
*/
if (tmp->flags & SD_POWERSAVINGS_BALANCE)
break;
if (tmp->flags & flag)
sd = tmp;
}
while (sd) {
cpumask_t span;
struct sched_group *group;
int new_cpu, weight;
if (!(sd->flags & flag)) {
sd = sd->child;
continue;
}
span = sd->span;
group = find_idlest_group(sd, t, cpu);
if (!group) {
sd = sd->child;
continue;
}
new_cpu = find_idlest_cpu(group, t, cpu);
if (new_cpu == -1 || new_cpu == cpu) {
/* Now try balancing at a lower domain level of cpu */
sd = sd->child;
continue;
}
/* Now try balancing at a lower domain level of new_cpu */
cpu = new_cpu;
sd = NULL;
weight = cpus_weight(span);
for_each_domain(cpu, tmp) {
if (weight <= cpus_weight(tmp->span))
break;
if (tmp->flags & flag)
sd = tmp;
}
/* while loop will break here if sd == NULL */
}
return cpu;
}
#endif /* CONFIG_SMP */
/*
* wake_idle() will wake a task on an idle cpu if task->cpu is
* not idle and an idle cpu is available. The span of cpus to
* search starts with cpus closest then further out as needed,
* so we always favor a closer, idle cpu.
*
* Returns the CPU we should wake onto.
*/
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
static int wake_idle(int cpu, struct task_struct *p)
{
cpumask_t tmp;
struct sched_domain *sd;
int i;
/*
* If it is idle, then it is the best cpu to run this task.
*
* This cpu is also the best, if it has more than one task already.
* Siblings must be also busy(in most cases) as they didn't already
* pickup the extra load from this cpu and hence we need not check
* sibling runqueue info. This will avoid the checks and cache miss
* penalities associated with that.
*/
if (idle_cpu(cpu) || cpu_rq(cpu)->nr_running > 1)
return cpu;
for_each_domain(cpu, sd) {
if (sd->flags & SD_WAKE_IDLE) {
cpus_and(tmp, sd->span, p->cpus_allowed);
for_each_cpu_mask(i, tmp) {
if (idle_cpu(i))
return i;
}
}
else
break;
}
return cpu;
}
#else
static inline int wake_idle(int cpu, struct task_struct *p)
{
return cpu;
}
#endif
/***
* try_to_wake_up - wake up a thread
* @p: the to-be-woken-up thread
* @state: the mask of task states that can be woken
* @sync: do a synchronous wakeup?
*
* Put it on the run-queue if it's not already there. The "current"
* thread is always on the run-queue (except when the actual
* re-schedule is in progress), and as such you're allowed to do
* the simpler "current->state = TASK_RUNNING" to mark yourself
* runnable without the overhead of this.
*
* returns failure only if the task is already active.
*/
static int try_to_wake_up(struct task_struct *p, unsigned int state, int sync)
{
int cpu, this_cpu, success = 0;
unsigned long flags;
long old_state;
struct rq *rq;
#ifdef CONFIG_SMP
struct sched_domain *sd, *this_sd = NULL;
unsigned long load, this_load;
int new_cpu;
#endif
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
cpu = task_cpu(p);
this_cpu = smp_processor_id();
#ifdef CONFIG_SMP
if (unlikely(task_running(rq, p)))
goto out_activate;
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
if (cpu == this_cpu) {
schedstat_inc(rq, ttwu_local);
goto out_set_cpu;
}
for_each_domain(this_cpu, sd) {
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_remote);
this_sd = sd;
break;
}
}
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
/*
* Check for affine wakeup and passive balancing possibilities.
*/
if (this_sd) {
int idx = this_sd->wake_idx;
unsigned int imbalance;
imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
load = source_load(cpu, idx);
this_load = target_load(this_cpu, idx);
new_cpu = this_cpu; /* Wake to this CPU if we can */
if (this_sd->flags & SD_WAKE_AFFINE) {
unsigned long tl = this_load;
unsigned long tl_per_task;
tl_per_task = cpu_avg_load_per_task(this_cpu);
/*
* If sync wakeup then subtract the (maximum possible)
* effect of the currently running task from the load
* of the current CPU:
*/
if (sync)
tl -= current->load_weight;
if ((tl <= load &&
tl + target_load(cpu, idx) <= tl_per_task) ||
100*(tl + p->load_weight) <= imbalance*load) {
/*
* This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and
* there is no bad imbalance.
*/
schedstat_inc(this_sd, ttwu_move_affine);
goto out_set_cpu;
}
}
/*
* Start passive balancing when half the imbalance_pct
* limit is reached.
*/
if (this_sd->flags & SD_WAKE_BALANCE) {
if (imbalance*this_load <= 100*load) {
schedstat_inc(this_sd, ttwu_move_balance);
goto out_set_cpu;
}
}
}
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
out_set_cpu:
new_cpu = wake_idle(new_cpu, p);
if (new_cpu != cpu) {
set_task_cpu(p, new_cpu);
task_rq_unlock(rq, &flags);
/* might preempt at this point */
rq = task_rq_lock(p, &flags);
old_state = p->state;
if (!(old_state & state))
goto out;
if (p->array)
goto out_running;
this_cpu = smp_processor_id();
cpu = task_cpu(p);
}
out_activate:
#endif /* CONFIG_SMP */
if (old_state == TASK_UNINTERRUPTIBLE) {
rq->nr_uninterruptible--;
/*
* Tasks on involuntary sleep don't earn
* sleep_avg beyond just interactive state.
*/
p->sleep_type = SLEEP_NONINTERACTIVE;
} else
/*
* Tasks that have marked their sleep as noninteractive get
* woken up with their sleep average not weighted in an
* interactive way.
*/
if (old_state & TASK_NONINTERACTIVE)
p->sleep_type = SLEEP_NONINTERACTIVE;
activate_task(p, rq, cpu == this_cpu);
/*
* Sync wakeups (i.e. those types of wakeups where the waker
* has indicated that it will leave the CPU in short order)
* don't trigger a preemption, if the woken up task will run on
* this cpu. (in this case the 'I will reschedule' promise of
* the waker guarantees that the freshly woken up task is going
* to be considered on this CPU.)
*/
if (!sync || cpu != this_cpu) {
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
success = 1;
out_running:
p->state = TASK_RUNNING;
out:
task_rq_unlock(rq, &flags);
return success;
}
int fastcall wake_up_process(struct task_struct *p)
{
return try_to_wake_up(p, TASK_STOPPED | TASK_TRACED |
TASK_INTERRUPTIBLE | TASK_UNINTERRUPTIBLE, 0);
}
EXPORT_SYMBOL(wake_up_process);
int fastcall wake_up_state(struct task_struct *p, unsigned int state)
{
return try_to_wake_up(p, state, 0);
}
static void task_running_tick(struct rq *rq, struct task_struct *p);
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*/
void fastcall sched_fork(struct task_struct *p, int clone_flags)
{
int cpu = get_cpu();
#ifdef CONFIG_SMP
cpu = sched_balance_self(cpu, SD_BALANCE_FORK);
#endif
set_task_cpu(p, cpu);
/*
* We mark the process as running here, but have not actually
* inserted it onto the runqueue yet. This guarantees that
* nobody will actually run it, and a signal or other external
* event cannot wake it up and insert it on the runqueue either.
*/
p->state = TASK_RUNNING;
/*
* Make sure we do not leak PI boosting priority to the child:
*/
p->prio = current->normal_prio;
INIT_LIST_HEAD(&p->run_list);
p->array = NULL;
#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
if (unlikely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
p->oncpu = 0;
#endif
#ifdef CONFIG_PREEMPT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = 1;
#endif
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
* resulting in more scheduling fairness.
*/
local_irq_disable();
p->time_slice = (current->time_slice + 1) >> 1;
/*
* The remainder of the first timeslice might be recovered by
* the parent if the child exits early enough.
*/
p->first_time_slice = 1;
current->time_slice >>= 1;
p->timestamp = sched_clock();
if (unlikely(!current->time_slice)) {
/*
* This case is rare, it happens when the parent has only
* a single jiffy left from its timeslice. Taking the
* runqueue lock is not a problem.
*/
current->time_slice = 1;
task_running_tick(cpu_rq(cpu), current);
}
local_irq_enable();
put_cpu();
}
/*
* wake_up_new_task - wake up a newly created task for the first time.
*
* This function will do some initial scheduler statistics housekeeping
* that must be done for every newly created context, then puts the task
* on the runqueue and wakes it.
*/
void fastcall wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
{
struct rq *rq, *this_rq;
unsigned long flags;
int this_cpu, cpu;
rq = task_rq_lock(p, &flags);
BUG_ON(p->state != TASK_RUNNING);
this_cpu = smp_processor_id();
cpu = task_cpu(p);
/*
* We decrease the sleep average of forking parents
* and children as well, to keep max-interactive tasks
* from forking tasks that are max-interactive. The parent
* (current) is done further down, under its lock.
*/
p->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(p) *
CHILD_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
p->prio = effective_prio(p);
if (likely(cpu == this_cpu)) {
if (!(clone_flags & CLONE_VM)) {
/*
* The VM isn't cloned, so we're in a good position to
* do child-runs-first in anticipation of an exec. This
* usually avoids a lot of COW overhead.
*/
if (unlikely(!current->array))
__activate_task(p, rq);
else {
p->prio = current->prio;
p->normal_prio = current->normal_prio;
list_add_tail(&p->run_list, &current->run_list);
p->array = current->array;
p->array->nr_active++;
inc_nr_running(p, rq);
}
set_need_resched();
} else
/* Run child last */
__activate_task(p, rq);
/*
* We skip the following code due to cpu == this_cpu
*
* task_rq_unlock(rq, &flags);
* this_rq = task_rq_lock(current, &flags);
*/
this_rq = rq;
} else {
this_rq = cpu_rq(this_cpu);
/*
* Not the local CPU - must adjust timestamp. This should
* get optimised away in the !CONFIG_SMP case.
*/
p->timestamp = (p->timestamp - this_rq->most_recent_timestamp)
+ rq->most_recent_timestamp;
__activate_task(p, rq);
if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
/*
* Parent and child are on different CPUs, now get the
* parent runqueue to update the parent's ->sleep_avg:
*/
task_rq_unlock(rq, &flags);
this_rq = task_rq_lock(current, &flags);
}
current->sleep_avg = JIFFIES_TO_NS(CURRENT_BONUS(current) *
PARENT_PENALTY / 100 * MAX_SLEEP_AVG / MAX_BONUS);
task_rq_unlock(this_rq, &flags);
}
/*
* Potentially available exiting-child timeslices are
* retrieved here - this way the parent does not get
* penalized for creating too many threads.
*
* (this cannot be used to 'generate' timeslices
* artificially, because any timeslice recovered here
* was given away by the parent in the first place.)
*/
void fastcall sched_exit(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
/*
* If the child was a (relative-) CPU hog then decrease
* the sleep_avg of the parent as well.
*/
rq = task_rq_lock(p->parent, &flags);
if (p->first_time_slice && task_cpu(p) == task_cpu(p->parent)) {
p->parent->time_slice += p->time_slice;
if (unlikely(p->parent->time_slice > task_timeslice(p)))
p->parent->time_slice = task_timeslice(p);
}
if (p->sleep_avg < p->parent->sleep_avg)
p->parent->sleep_avg = p->parent->sleep_avg /
(EXIT_WEIGHT + 1) * EXIT_WEIGHT + p->sleep_avg /
(EXIT_WEIGHT + 1);
task_rq_unlock(rq, &flags);
}
/**
* prepare_task_switch - prepare to switch tasks
* @rq: the runqueue preparing to switch
* @next: the task we are going to switch to.
*
* This is called with the rq lock held and interrupts off. It must
* be paired with a subsequent finish_task_switch after the context
* switch.
*
* prepare_task_switch sets up locking and calls architecture specific
* hooks.
*/
static inline void prepare_task_switch(struct rq *rq, struct task_struct *next)
{
prepare_lock_switch(rq, next);
prepare_arch_switch(next);
}
/**
* finish_task_switch - clean up after a task-switch
* @rq: runqueue associated with task-switch
* @prev: the thread we just switched away from.
*
* finish_task_switch must be called after the context switch, paired
* with a prepare_task_switch call before the context switch.
* finish_task_switch will reconcile locking set up by prepare_task_switch,
* and do any other architecture-specific cleanup actions.
*
* Note that we may have delayed dropping an mm in context_switch(). If
* so, we finish that here outside of the runqueue lock. (Doing it
* with the lock held can cause deadlocks; see schedule() for
* details.)
*/
static inline void finish_task_switch(struct rq *rq, struct task_struct *prev)
__releases(rq->lock)
{
struct mm_struct *mm = rq->prev_mm;
long prev_state;
rq->prev_mm = NULL;
/*
* A task struct has one reference for the use as "current".
* If a task dies, then it sets TASK_DEAD in tsk->state and calls
* schedule one last time. The schedule call will never return, and
* the scheduled task must drop that reference.
* The test for TASK_DEAD must occur while the runqueue locks are
* still held, otherwise prev could be scheduled on another cpu, die
* there before we look at prev->state, and then the reference would
* be dropped twice.
* Manfred Spraul <manfred@colorfullife.com>
*/
prev_state = prev->state;
finish_arch_switch(prev);
finish_lock_switch(rq, prev);
if (mm)
mmdrop(mm);
if (unlikely(prev_state == TASK_DEAD)) {
/*
* Remove function-return probe instances associated with this
* task and put them back on the free list.
*/
kprobe_flush_task(prev);
put_task_struct(prev);
}
}
/**
* schedule_tail - first thing a freshly forked thread must call.
* @prev: the thread we just switched away from.
*/
asmlinkage void schedule_tail(struct task_struct *prev)
__releases(rq->lock)
{
struct rq *rq = this_rq();
finish_task_switch(rq, prev);
#ifdef __ARCH_WANT_UNLOCKED_CTXSW
/* In this case, finish_task_switch does not reenable preemption */
preempt_enable();
#endif
if (current->set_child_tid)
put_user(current->pid, current->set_child_tid);
}
/*
* context_switch - switch to the new MM and the new
* thread's register state.
*/
static inline struct task_struct *
context_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
struct mm_struct *mm = next->mm;
struct mm_struct *oldmm = prev->active_mm;
/*
* For paravirt, this is coupled with an exit in switch_to to
* combine the page table reload and the switch backend into
* one hypercall.
*/
arch_enter_lazy_cpu_mode();
if (!mm) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
if (!prev->mm) {
prev->active_mm = NULL;
WARN_ON(rq->prev_mm);
rq->prev_mm = oldmm;
}
/*
* Since the runqueue lock will be released by the next
* task (which is an invalid locking op but in the case
* of the scheduler it's an obvious special-case), so we
* do an early lockdep release here:
*/
#ifndef __ARCH_WANT_UNLOCKED_CTXSW
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
#endif
/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);
return prev;
}
/*
* nr_running, nr_uninterruptible and nr_context_switches:
*
* externally visible scheduler statistics: current number of runnable
* threads, current number of uninterruptible-sleeping threads, total
* number of context switches performed since bootup.
*/
unsigned long nr_running(void)
{
unsigned long i, sum = 0;
for_each_online_cpu(i)
sum += cpu_rq(i)->nr_running;
return sum;
}
unsigned long nr_uninterruptible(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_uninterruptible;
/*
* Since we read the counters lockless, it might be slightly
* inaccurate. Do not allow it to go below zero though:
*/
if (unlikely((long)sum < 0))
sum = 0;
return sum;
}
unsigned long long nr_context_switches(void)
{
int i;
unsigned long long sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_switches;
return sum;
}
unsigned long nr_iowait(void)
{
unsigned long i, sum = 0;
for_each_possible_cpu(i)
sum += atomic_read(&cpu_rq(i)->nr_iowait);
return sum;
}
unsigned long nr_active(void)
{
unsigned long i, running = 0, uninterruptible = 0;
for_each_online_cpu(i) {
running += cpu_rq(i)->nr_running;
uninterruptible += cpu_rq(i)->nr_uninterruptible;
}
if (unlikely((long)uninterruptible < 0))
uninterruptible = 0;
return running + uninterruptible;
}
#ifdef CONFIG_SMP
/*
* Is this task likely cache-hot:
*/
static inline int
task_hot(struct task_struct *p, unsigned long long now, struct sched_domain *sd)
{
return (long long)(now - p->last_ran) < (long long)sd->cache_hot_time;
}
/*
* double_rq_lock - safely lock two runqueues
*
* Note this does not disable interrupts like task_rq_lock,
* you need to do so manually before calling.
*/
static void double_rq_lock(struct rq *rq1, struct rq *rq2)
__acquires(rq1->lock)
__acquires(rq2->lock)
{
BUG_ON(!irqs_disabled());
if (rq1 == rq2) {
spin_lock(&rq1->lock);
__acquire(rq2->lock); /* Fake it out ;) */
} else {
if (rq1 < rq2) {
spin_lock(&rq1->lock);
spin_lock(&rq2->lock);
} else {
spin_lock(&rq2->lock);
spin_lock(&rq1->lock);
}
}
}
/*
* double_rq_unlock - safely unlock two runqueues
*
* Note this does not restore interrupts like task_rq_unlock,
* you need to do so manually after calling.
*/
static void double_rq_unlock(struct rq *rq1, struct rq *rq2)
__releases(rq1->lock)
__releases(rq2->lock)
{
spin_unlock(&rq1->lock);
if (rq1 != rq2)
spin_unlock(&rq2->lock);
else
__release(rq2->lock);
}
/*
* double_lock_balance - lock the busiest runqueue, this_rq is locked already.
*/
static void double_lock_balance(struct rq *this_rq, struct rq *busiest)
__releases(this_rq->lock)
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
if (unlikely(!irqs_disabled())) {
/* printk() doesn't work good under rq->lock */
spin_unlock(&this_rq->lock);
BUG_ON(1);
}
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest < this_rq) {
spin_unlock(&this_rq->lock);
spin_lock(&busiest->lock);
spin_lock(&this_rq->lock);
} else
spin_lock(&busiest->lock);
}
}
/*
* If dest_cpu is allowed for this process, migrate the task to it.
* This is accomplished by forcing the cpu_allowed mask to only
* allow dest_cpu, which will force the cpu onto dest_cpu. Then
* the cpu_allowed mask is restored.
*/
static void sched_migrate_task(struct task_struct *p, int dest_cpu)
{
struct migration_req req;
unsigned long flags;
struct rq *rq;
rq = task_rq_lock(p, &flags);
if (!cpu_isset(dest_cpu, p->cpus_allowed)
|| unlikely(cpu_is_offline(dest_cpu)))
goto out;
/* force the process onto the specified CPU */
if (migrate_task(p, dest_cpu, &req)) {
/* Need to wait for migration thread (might exit: take ref). */
struct task_struct *mt = rq->migration_thread;
get_task_struct(mt);
task_rq_unlock(rq, &flags);
wake_up_process(mt);
put_task_struct(mt);
wait_for_completion(&req.done);
return;
}
out:
task_rq_unlock(rq, &flags);
}
/*
* sched_exec - execve() is a valuable balancing opportunity, because at
* this point the task has the smallest effective memory and cache footprint.
*/
void sched_exec(void)
{
int new_cpu, this_cpu = get_cpu();
new_cpu = sched_balance_self(this_cpu, SD_BALANCE_EXEC);
put_cpu();
if (new_cpu != this_cpu)
sched_migrate_task(current, new_cpu);
}
/*
* pull_task - move a task from a remote runqueue to the local runqueue.
* Both runqueues must be locked.
*/
static void pull_task(struct rq *src_rq, struct prio_array *src_array,
struct task_struct *p, struct rq *this_rq,
struct prio_array *this_array, int this_cpu)
{
dequeue_task(p, src_array);
dec_nr_running(p, src_rq);
set_task_cpu(p, this_cpu);
inc_nr_running(p, this_rq);
enqueue_task(p, this_array);
p->timestamp = (p->timestamp - src_rq->most_recent_timestamp)
+ this_rq->most_recent_timestamp;
/*
* Note that idle threads have a prio of MAX_PRIO, for this test
* to be always true for them.
*/
if (TASK_PREEMPTS_CURR(p, this_rq))
resched_task(this_rq->curr);
}
/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
*/
static
int can_migrate_task(struct task_struct *p, struct rq *rq, int this_cpu,
struct sched_domain *sd, enum idle_type idle,
int *all_pinned)
{
/*
* We do not migrate tasks that are:
* 1) running (obviously), or
* 2) cannot be migrated to this CPU due to cpus_allowed, or
* 3) are cache-hot on their current CPU.
*/
if (!cpu_isset(this_cpu, p->cpus_allowed))
return 0;
*all_pinned = 0;
if (task_running(rq, p))
return 0;
/*
* Aggressive migration if:
* 1) task is cache cold, or
* 2) too many balance attempts have failed.
*/
if (sd->nr_balance_failed > sd->cache_nice_tries) {
#ifdef CONFIG_SCHEDSTATS
if (task_hot(p, rq->most_recent_timestamp, sd))
schedstat_inc(sd, lb_hot_gained[idle]);
#endif
return 1;
}
if (task_hot(p, rq->most_recent_timestamp, sd))
return 0;
return 1;
}
#define rq_best_prio(rq) min((rq)->curr->prio, (rq)->best_expired_prio)
/*
* move_tasks tries to move up to max_nr_move tasks and max_load_move weighted
* load from busiest to this_rq, as part of a balancing operation within
* "domain". Returns the number of tasks moved.
*
* Called with both runqueues locked.
*/
static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
unsigned long max_nr_move, unsigned long max_load_move,
struct sched_domain *sd, enum idle_type idle,
int *all_pinned)
{
int idx, pulled = 0, pinned = 0, this_best_prio, best_prio,
best_prio_seen, skip_for_load;
struct prio_array *array, *dst_array;
struct list_head *head, *curr;
struct task_struct *tmp;
long rem_load_move;
if (max_nr_move == 0 || max_load_move == 0)
goto out;
rem_load_move = max_load_move;
pinned = 1;
this_best_prio = rq_best_prio(this_rq);
best_prio = rq_best_prio(busiest);
/*
* Enable handling of the case where there is more than one task
* with the best priority. If the current running task is one
* of those with prio==best_prio we know it won't be moved
* and therefore it's safe to override the skip (based on load) of
* any task we find with that prio.
*/
best_prio_seen = best_prio == busiest->curr->prio;
/*
* We first consider expired tasks. Those will likely not be
* executed in the near future, and they are most likely to
* be cache-cold, thus switching CPUs has the least effect
* on them.
*/
if (busiest->expired->nr_active) {
array = busiest->expired;
dst_array = this_rq->expired;
} else {
array = busiest->active;
dst_array = this_rq->active;
}
new_array:
/* Start searching at priority 0: */
idx = 0;
skip_bitmap:
if (!idx)
idx = sched_find_first_bit(array->bitmap);
else
idx = find_next_bit(array->bitmap, MAX_PRIO, idx);
if (idx >= MAX_PRIO) {
if (array == busiest->expired && busiest->active->nr_active) {
array = busiest->active;
dst_array = this_rq->active;
goto new_array;
}
goto out;
}
head = array->queue + idx;
curr = head->prev;
skip_queue:
tmp = list_entry(curr, struct task_struct, run_list);
curr = curr->prev;
/*
* To help distribute high priority tasks accross CPUs we don't
* skip a task if it will be the highest priority task (i.e. smallest
* prio value) on its new queue regardless of its load weight
*/
skip_for_load = tmp->load_weight > rem_load_move;
if (skip_for_load && idx < this_best_prio)
skip_for_load = !best_prio_seen && idx == best_prio;
if (skip_for_load ||
!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) {
best_prio_seen |= idx == best_prio;
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu);
pulled++;
rem_load_move -= tmp->load_weight;
/*
* We only want to steal up to the prescribed number of tasks
* and the prescribed amount of weighted load.
*/
if (pulled < max_nr_move && rem_load_move > 0) {
if (idx < this_best_prio)
this_best_prio = idx;
if (curr != head)
goto skip_queue;
idx++;
goto skip_bitmap;
}
out:
/*
* Right now, this is the only place pull_task() is called,
* so we can safely collect pull_task() stats here rather than
* inside pull_task().
*/
schedstat_add(sd, lb_gained[idle], pulled);
if (all_pinned)
*all_pinned = pinned;
return pulled;
}
/*
* find_busiest_group finds and returns the busiest CPU group within the
* domain. It calculates and returns the amount of weighted load which
* should be moved to restore balance via the imbalance parameter.
*/
static struct sched_group *
find_busiest_group(struct sched_domain *sd, int this_cpu,
unsigned long *imbalance, enum idle_type idle, int *sd_idle,
cpumask_t *cpus, int *balance)
{
struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups;
unsigned long max_load, avg_load, total_load, this_load, total_pwr;
unsigned long max_pull;
unsigned long busiest_load_per_task, busiest_nr_running;
unsigned long this_load_per_task, this_nr_running;
int load_idx;
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
int power_savings_balance = 1;
unsigned long leader_nr_running = 0, min_load_per_task = 0;
unsigned long min_nr_running = ULONG_MAX;
struct sched_group *group_min = NULL, *group_leader = NULL;
#endif
max_load = this_load = total_load = total_pwr = 0;
busiest_load_per_task = busiest_nr_running = 0;
this_load_per_task = this_nr_running = 0;
if (idle == NOT_IDLE)
load_idx = sd->busy_idx;
else if (idle == NEWLY_IDLE)
load_idx = sd->newidle_idx;
else
load_idx = sd->idle_idx;
do {
unsigned long load, group_capacity;
int local_group;
int i;
unsigned int balance_cpu = -1, first_idle_cpu = 0;
unsigned long sum_nr_running, sum_weighted_load;
local_group = cpu_isset(this_cpu, group->cpumask);
if (local_group)
balance_cpu = first_cpu(group->cpumask);
/* Tally up the load of all CPUs in the group */
sum_weighted_load = sum_nr_running = avg_load = 0;
for_each_cpu_mask(i, group->cpumask) {
struct rq *rq;
if (!cpu_isset(i, *cpus))
continue;
rq = cpu_rq(i);
if (*sd_idle && !idle_cpu(i))
*sd_idle = 0;
/* Bias balancing toward cpus of our domain */
if (local_group) {
if (idle_cpu(i) && !first_idle_cpu) {
first_idle_cpu = 1;
balance_cpu = i;
}
load = target_load(i, load_idx);
} else
load = source_load(i, load_idx);
avg_load += load;
sum_nr_running += rq->nr_running;
sum_weighted_load += rq->raw_weighted_load;
}
/*
* First idle cpu or the first cpu(busiest) in this sched group
* is eligible for doing load balancing at this and above
* domains.
*/
if (local_group && balance_cpu != this_cpu && balance) {
*balance = 0;
goto ret;
}
total_load += avg_load;
total_pwr += group->__cpu_power;
/* Adjust by relative CPU power of the group */
avg_load = sg_div_cpu_power(group,
avg_load * SCHED_LOAD_SCALE);
group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
if (local_group) {
this_load = avg_load;
this = group;
this_nr_running = sum_nr_running;
this_load_per_task = sum_weighted_load;
} else if (avg_load > max_load &&
sum_nr_running > group_capacity) {
max_load = avg_load;
busiest = group;
busiest_nr_running = sum_nr_running;
busiest_load_per_task = sum_weighted_load;
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/*
* Busy processors will not participate in power savings
* balance.
*/
if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
goto group_next;
/*
* If the local group is idle or completely loaded
* no need to do power savings balance at this domain
*/
if (local_group && (this_nr_running >= group_capacity ||
!this_nr_running))
power_savings_balance = 0;
/*
* If a group is already running at full capacity or idle,
* don't include that group in power savings calculations
*/
if (!power_savings_balance || sum_nr_running >= group_capacity
|| !sum_nr_running)
goto group_next;
/*
* Calculate the group which has the least non-idle load.
* This is the group from where we need to pick up the load
* for saving power
*/
if ((sum_nr_running < min_nr_running) ||
(sum_nr_running == min_nr_running &&
first_cpu(group->cpumask) <
first_cpu(group_min->cpumask))) {
group_min = group;
min_nr_running = sum_nr_running;
min_load_per_task = sum_weighted_load /
sum_nr_running;
}
/*
* Calculate the group which is almost near its
* capacity but still has some space to pick up some load
* from other group and save more power
*/
if (sum_nr_running <= group_capacity - 1) {
if (sum_nr_running > leader_nr_running ||
(sum_nr_running == leader_nr_running &&
first_cpu(group->cpumask) >
first_cpu(group_leader->cpumask))) {
group_leader = group;
leader_nr_running = sum_nr_running;
}
}
group_next:
#endif
group = group->next;
} while (group != sd->groups);
if (!busiest || this_load >= max_load || busiest_nr_running == 0)
goto out_balanced;
avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr;
if (this_load >= avg_load ||
100*max_load <= sd->imbalance_pct*this_load)
goto out_balanced;
busiest_load_per_task /= busiest_nr_running;
/*
* We're trying to get all the cpus to the average_load, so we don't
* want to push ourselves above the average load, nor do we wish to
* reduce the max loaded cpu below the average load, as either of these
* actions would just result in more rebalancing later, and ping-pong
* tasks around. Thus we look for the minimum possible imbalance.
* Negative imbalances (*we* are more loaded than anyone else) will
* be counted as no imbalance for these purposes -- we can't fix that
* by pulling tasks to us. Be careful of negative numbers as they'll
* appear as very large values with unsigned longs.
*/
if (max_load <= busiest_load_per_task)
goto out_balanced;
/*
* In the presence of smp nice balancing, certain scenarios can have
* max load less than avg load(as we skip the groups at or below
* its cpu_power, while calculating max_load..)
*/
if (max_load < avg_load) {
*imbalance = 0;
goto small_imbalance;
}
/* Don't want to pull so many tasks that a group would go idle */
max_pull = min(max_load - avg_load, max_load - busiest_load_per_task);
/* How much load to actually move to equalise the imbalance */
*imbalance = min(max_pull * busiest->__cpu_power,
(avg_load - this_load) * this->__cpu_power)
/ SCHED_LOAD_SCALE;
/*
* if *imbalance is less than the average load per runnable task
* there is no gaurantee that any tasks will be moved so we'll have
* a think about bumping its value to force at least one task to be
* moved
*/
if (*imbalance < busiest_load_per_task) {
unsigned long tmp, pwr_now, pwr_move;
unsigned int imbn;
small_imbalance:
pwr_move = pwr_now = 0;
imbn = 2;
if (this_nr_running) {
this_load_per_task /= this_nr_running;
if (busiest_load_per_task > this_load_per_task)
imbn = 1;
} else
this_load_per_task = SCHED_LOAD_SCALE;
if (max_load - this_load >= busiest_load_per_task * imbn) {
*imbalance = busiest_load_per_task;
return busiest;
}
/*
* OK, we don't have enough imbalance to justify moving tasks,
* however we may be able to increase total CPU power used by
* moving them.
*/
pwr_now += busiest->__cpu_power *
min(busiest_load_per_task, max_load);
pwr_now += this->__cpu_power *
min(this_load_per_task, this_load);
pwr_now /= SCHED_LOAD_SCALE;
/* Amount of load we'd subtract */
tmp = sg_div_cpu_power(busiest,
busiest_load_per_task * SCHED_LOAD_SCALE);
if (max_load > tmp)
pwr_move += busiest->__cpu_power *
min(busiest_load_per_task, max_load - tmp);
/* Amount of load we'd add */
if (max_load * busiest->__cpu_power <
busiest_load_per_task * SCHED_LOAD_SCALE)
tmp = sg_div_cpu_power(this,
max_load * busiest->__cpu_power);
else
tmp = sg_div_cpu_power(this,
busiest_load_per_task * SCHED_LOAD_SCALE);
pwr_move += this->__cpu_power *
min(this_load_per_task, this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain throughput */
if (pwr_move <= pwr_now)
goto out_balanced;
*imbalance = busiest_load_per_task;
}
return busiest;
out_balanced:
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
if (idle == NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
goto ret;
if (this == group_leader && group_leader != group_min) {
*imbalance = min_load_per_task;
return group_min;
}
#endif
ret:
*imbalance = 0;
return NULL;
}
/*
* find_busiest_queue - find the busiest runqueue among the cpus in group.
*/
static struct rq *
find_busiest_queue(struct sched_group *group, enum idle_type idle,
unsigned long imbalance, cpumask_t *cpus)
{
struct rq *busiest = NULL, *rq;
unsigned long max_load = 0;
int i;
for_each_cpu_mask(i, group->cpumask) {
if (!cpu_isset(i, *cpus))
continue;
rq = cpu_rq(i);
if (rq->nr_running == 1 && rq->raw_weighted_load > imbalance)
continue;
if (rq->raw_weighted_load > max_load) {
max_load = rq->raw_weighted_load;
busiest = rq;
}
}
return busiest;
}
/*
* Max backoff if we encounter pinned tasks. Pretty arbitrary value, but
* so long as it is large enough.
*/
#define MAX_PINNED_INTERVAL 512
static inline unsigned long minus_1_or_zero(unsigned long n)
{
return n > 0 ? n - 1 : 0;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*/
static int load_balance(int this_cpu, struct rq *this_rq,
struct sched_domain *sd, enum idle_type idle,
int *balance)
{
int nr_moved, all_pinned = 0, active_balance = 0, sd_idle = 0;
struct sched_group *group;
unsigned long imbalance;
struct rq *busiest;
cpumask_t cpus = CPU_MASK_ALL;
unsigned long flags;
/*
* When power savings policy is enabled for the parent domain, idle
* sibling can pick up load irrespective of busy siblings. In this case,
* let the state of idle sibling percolate up as IDLE, instead of
* portraying it as NOT_IDLE.
*/
if (idle != NOT_IDLE && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
sd_idle = 1;
schedstat_inc(sd, lb_cnt[idle]);
redo:
group = find_busiest_group(sd, this_cpu, &imbalance, idle, &sd_idle,
&cpus, balance);
if (*balance == 0)
goto out_balanced;
if (!group) {
schedstat_inc(sd, lb_nobusyg[idle]);
goto out_balanced;
}
busiest = find_busiest_queue(group, idle, imbalance, &cpus);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[idle]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[idle], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/*
* Attempt to move tasks. If find_busiest_group has found
* an imbalance but busiest->nr_running <= 1, the group is
* still unbalanced. nr_moved simply stays zero, so it is
* correctly treated as an imbalance.
*/
local_irq_save(flags);
double_rq_lock(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
minus_1_or_zero(busiest->nr_running),
imbalance, sd, idle, &all_pinned);
double_rq_unlock(this_rq, busiest);
local_irq_restore(flags);
/*
* some other cpu did the load balance for us.
*/
if (nr_moved && this_cpu != smp_processor_id())
resched_cpu(this_cpu);
/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(all_pinned)) {
cpu_clear(cpu_of(busiest), cpus);
if (!cpus_empty(cpus))
goto redo;
goto out_balanced;
}
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[idle]);
sd->nr_balance_failed++;
if (unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2)) {
spin_lock_irqsave(&busiest->lock, flags);
/* don't kick the migration_thread, if the curr
* task on busiest cpu can't be moved to this_cpu
*/
if (!cpu_isset(this_cpu, busiest->curr->cpus_allowed)) {
spin_unlock_irqrestore(&busiest->lock, flags);
all_pinned = 1;
goto out_one_pinned;
}
if (!busiest->active_balance) {
busiest->active_balance = 1;
busiest->push_cpu = this_cpu;
active_balance = 1;
}
spin_unlock_irqrestore(&busiest->lock, flags);
if (active_balance)
wake_up_process(busiest->migration_thread);
/*
* We've kicked active balancing, reset the failure
* counter.
*/
sd->nr_balance_failed = sd->cache_nice_tries+1;
}
} else
sd->nr_balance_failed = 0;
if (likely(!active_balance)) {
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
} else {
/*
* If we've begun active balancing, start to back off. This
* case may not be covered by the all_pinned logic if there
* is only 1 task on the busy runqueue (because we don't call
* move_tasks).
*/
if (sd->balance_interval < sd->max_interval)
sd->balance_interval *= 2;
}
if (!nr_moved && !sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
return -1;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[idle]);
sd->nr_balance_failed = 0;
out_one_pinned:
/* tune up the balancing interval */
if ((all_pinned && sd->balance_interval < MAX_PINNED_INTERVAL) ||
(sd->balance_interval < sd->max_interval))
sd->balance_interval *= 2;
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
return -1;
return 0;
}
/*
* Check this_cpu to ensure it is balanced within domain. Attempt to move
* tasks if there is an imbalance.
*
* Called from schedule when this_rq is about to become idle (NEWLY_IDLE).
* this_rq is locked.
*/
static int
load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
{
struct sched_group *group;
struct rq *busiest = NULL;
unsigned long imbalance;
int nr_moved = 0;
int sd_idle = 0;
cpumask_t cpus = CPU_MASK_ALL;
/*
* When power savings policy is enabled for the parent domain, idle
* sibling can pick up load irrespective of busy siblings. In this case,
* let the state of idle sibling percolate up as IDLE, instead of
* portraying it as NOT_IDLE.
*/
if (sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
sd_idle = 1;
schedstat_inc(sd, lb_cnt[NEWLY_IDLE]);
redo:
group = find_busiest_group(sd, this_cpu, &imbalance, NEWLY_IDLE,
&sd_idle, &cpus, NULL);
if (!group) {
schedstat_inc(sd, lb_nobusyg[NEWLY_IDLE]);
goto out_balanced;
}
busiest = find_busiest_queue(group, NEWLY_IDLE, imbalance,
&cpus);
if (!busiest) {
schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]);
goto out_balanced;
}
BUG_ON(busiest == this_rq);
schedstat_add(sd, lb_imbalance[NEWLY_IDLE], imbalance);
nr_moved = 0;
if (busiest->nr_running > 1) {
/* Attempt to move tasks */
double_lock_balance(this_rq, busiest);
nr_moved = move_tasks(this_rq, this_cpu, busiest,
minus_1_or_zero(busiest->nr_running),
imbalance, sd, NEWLY_IDLE, NULL);
spin_unlock(&busiest->lock);
if (!nr_moved) {
cpu_clear(cpu_of(busiest), cpus);
if (!cpus_empty(cpus))
goto redo;
}
}
if (!nr_moved) {
schedstat_inc(sd, lb_failed[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
return -1;
} else
sd->nr_balance_failed = 0;
return nr_moved;
out_balanced:
schedstat_inc(sd, lb_balanced[NEWLY_IDLE]);
if (!sd_idle && sd->flags & SD_SHARE_CPUPOWER &&
!test_sd_parent(sd, SD_POWERSAVINGS_BALANCE))
return -1;
sd->nr_balance_failed = 0;
return 0;
}
/*
* idle_balance is called by schedule() if this_cpu is about to become
* idle. Attempts to pull tasks from other CPUs.
*/
static void idle_balance(int this_cpu, struct rq *this_rq)
{
struct sched_domain *sd;
int pulled_task = 0;
unsigned long next_balance = jiffies + 60 * HZ;
for_each_domain(this_cpu, sd) {
if (sd->flags & SD_BALANCE_NEWIDLE) {
/* If we've pulled tasks over stop searching: */
pulled_task = load_balance_newidle(this_cpu,
this_rq, sd);
if (time_after(next_balance,
sd->last_balance + sd->balance_interval))
next_balance = sd->last_balance
+ sd->balance_interval;
if (pulled_task)
break;
}
}
if (!pulled_task)
/*
* We are going idle. next_balance may be set based on
* a busy processor. So reset next_balance.
*/
this_rq->next_balance = next_balance;
}
/*
* active_load_balance is run by migration threads. It pushes running tasks
* off the busiest CPU onto idle CPUs. It requires at least 1 task to be
* running on each physical CPU where possible, and avoids physical /
* logical imbalances.
*
* Called with busiest_rq locked.
*/
static void active_load_balance(struct rq *busiest_rq, int busiest_cpu)
{
int target_cpu = busiest_rq->push_cpu;
struct sched_domain *sd;
struct rq *target_rq;
/* Is there any task to move? */
if (busiest_rq->nr_running <= 1)
return;
target_rq = cpu_rq(target_cpu);
/*
* This condition is "impossible", if it occurs
* we need to fix it. Originally reported by
* Bjorn Helgaas on a 128-cpu setup.
*/
BUG_ON(busiest_rq == target_rq);
/* move a task from busiest_rq to target_rq */
double_lock_balance(busiest_rq, target_rq);
/* Search for an sd spanning us and the target CPU. */
for_each_domain(target_cpu, sd) {
if ((sd->flags & SD_LOAD_BALANCE) &&
cpu_isset(busiest_cpu, sd->span))
break;
}
if (likely(sd)) {
schedstat_inc(sd, alb_cnt);
if (move_tasks(target_rq, target_cpu, busiest_rq, 1,
RTPRIO_TO_LOAD_WEIGHT(100), sd, SCHED_IDLE,
NULL))
schedstat_inc(sd, alb_pushed);
else
schedstat_inc(sd, alb_failed);
}
spin_unlock(&target_rq->lock);
}
static void update_load(struct rq *this_rq)
{
unsigned long this_load;
unsigned int i, scale;
this_load = this_rq->raw_weighted_load;
/* Update our load: */
for (i = 0, scale = 1; i < 3; i++, scale += scale) {
unsigned long old_load, new_load;
/* scale is effectively 1 << i now, and >> i divides by scale */
old_load = this_rq->cpu_load[i];
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
if (new_load > old_load)
new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
}
}
#ifdef CONFIG_NO_HZ
static struct {
atomic_t load_balancer;
cpumask_t cpu_mask;
} nohz ____cacheline_aligned = {
.load_balancer = ATOMIC_INIT(-1),
.cpu_mask = CPU_MASK_NONE,
};
/*
* This routine will try to nominate the ilb (idle load balancing)
* owner among the cpus whose ticks are stopped. ilb owner will do the idle
* load balancing on behalf of all those cpus. If all the cpus in the system
* go into this tickless mode, then there will be no ilb owner (as there is
* no need for one) and all the cpus will sleep till the next wakeup event
* arrives...
*
* For the ilb owner, tick is not stopped. And this tick will be used
* for idle load balancing. ilb owner will still be part of
* nohz.cpu_mask..
*
* While stopping the tick, this cpu will become the ilb owner if there
* is no other owner. And will be the owner till that cpu becomes busy
* or if all cpus in the system stop their ticks at which point
* there is no need for ilb owner.
*
* When the ilb owner becomes busy, it nominates another owner, during the
* next busy scheduler_tick()
*/
int select_nohz_load_balancer(int stop_tick)
{
int cpu = smp_processor_id();
if (stop_tick) {
cpu_set(cpu, nohz.cpu_mask);
cpu_rq(cpu)->in_nohz_recently = 1;
/*
* If we are going offline and still the leader, give up!
*/
if (cpu_is_offline(cpu) &&
atomic_read(&nohz.load_balancer) == cpu) {
if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
BUG();
return 0;
}
/* time for ilb owner also to sleep */
if (cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
if (atomic_read(&nohz.load_balancer) == cpu)
atomic_set(&nohz.load_balancer, -1);
return 0;
}
if (atomic_read(&nohz.load_balancer) == -1) {
/* make me the ilb owner */
if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
return 1;
} else if (atomic_read(&nohz.load_balancer) == cpu)
return 1;
} else {
if (!cpu_isset(cpu, nohz.cpu_mask))
return 0;
cpu_clear(cpu, nohz.cpu_mask);
if (atomic_read(&nohz.load_balancer) == cpu)
if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
BUG();
}
return 0;
}
#endif
static DEFINE_SPINLOCK(balancing);
/*
* It checks each scheduling domain to see if it is due to be balanced,
* and initiates a balancing operation if so.
*
* Balancing parameters are set up in arch_init_sched_domains.
*/
static inline void rebalance_domains(int cpu, enum idle_type idle)
{
int balance = 1;
struct rq *rq = cpu_rq(cpu);
unsigned long interval;
struct sched_domain *sd;
/* Earliest time when we have to do rebalance again */
unsigned long next_balance = jiffies + 60*HZ;
for_each_domain(cpu, sd) {
if (!(sd->flags & SD_LOAD_BALANCE))
continue;
interval = sd->balance_interval;
if (idle != SCHED_IDLE)
interval *= sd->busy_factor;
/* scale ms to jiffies */
interval = msecs_to_jiffies(interval);
if (unlikely(!interval))
interval = 1;
if (sd->flags & SD_SERIALIZE) {
if (!spin_trylock(&balancing))
goto out;
}
if (time_after_eq(jiffies, sd->last_balance + interval)) {
if (load_balance(cpu, rq, sd, idle, &balance)) {
/*
* We've pulled tasks over so either we're no
* longer idle, or one of our SMT siblings is
* not idle.
*/
idle = NOT_IDLE;
}
sd->last_balance = jiffies;
}
if (sd->flags & SD_SERIALIZE)
spin_unlock(&balancing);
out:
if (time_after(next_balance, sd->last_balance + interval))
next_balance = sd->last_balance + interval;
/*
* Stop the load balance at this level. There is another
* CPU in our sched group which is doing load balancing more
* actively.
*/
if (!balance)
break;
}
rq->next_balance = next_balance;
}
/*
* run_rebalance_domains is triggered when needed from the scheduler tick.
* In CONFIG_NO_HZ case, the idle load balance owner will do the
* rebalancing for all the cpus for whom scheduler ticks are stopped.
*/
static void run_rebalance_domains(struct softirq_action *h)
{
int local_cpu = smp_processor_id();
struct rq *local_rq = cpu_rq(local_cpu);
enum idle_type idle = local_rq->idle_at_tick ? SCHED_IDLE : NOT_IDLE;
rebalance_domains(local_cpu, idle);
#ifdef CONFIG_NO_HZ
/*
* If this cpu is the owner for idle load balancing, then do the
* balancing on behalf of the other idle cpus whose ticks are
* stopped.
*/
if (local_rq->idle_at_tick &&
atomic_read(&nohz.load_balancer) == local_cpu) {
cpumask_t cpus = nohz.cpu_mask;
struct rq *rq;
int balance_cpu;
cpu_clear(local_cpu, cpus);
for_each_cpu_mask(balance_cpu, cpus) {
/*
* If this cpu gets work to do, stop the load balancing
* work being done for other cpus. Next load
* balancing owner will pick it up.
*/
if (need_resched())
break;
rebalance_domains(balance_cpu, SCHED_IDLE);
rq = cpu_rq(balance_cpu);
if (time_after(local_rq->next_balance, rq->next_balance))
local_rq->next_balance = rq->next_balance;
}
}
#endif
}
/*
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
*
* In case of CONFIG_NO_HZ, this is the place where we nominate a new
* idle load balancing owner or decide to stop the periodic load balancing,
* if the whole system is idle.
*/
static inline void trigger_load_balance(int cpu)
{
struct rq *rq = cpu_rq(cpu);
#ifdef CONFIG_NO_HZ
/*
* If we were in the nohz mode recently and busy at the current
* scheduler tick, then check if we need to nominate new idle
* load balancer.
*/
if (rq->in_nohz_recently && !rq->idle_at_tick) {
rq->in_nohz_recently = 0;
if (atomic_read(&nohz.load_balancer) == cpu) {
cpu_clear(cpu, nohz.cpu_mask);
atomic_set(&nohz.load_balancer, -1);
}
if (atomic_read(&nohz.load_balancer) == -1) {
/*
* simple selection for now: Nominate the
* first cpu in the nohz list to be the next
* ilb owner.
*
* TBD: Traverse the sched domains and nominate
* the nearest cpu in the nohz.cpu_mask.
*/
int ilb = first_cpu(nohz.cpu_mask);
if (ilb != NR_CPUS)
resched_cpu(ilb);
}
}
/*
* If this cpu is idle and doing idle load balancing for all the
* cpus with ticks stopped, is it time for that to stop?
*/
if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
cpus_weight(nohz.cpu_mask) == num_online_cpus()) {
resched_cpu(cpu);
return;
}
/*
* If this cpu is idle and the idle load balancing is done by
* someone else, then no need raise the SCHED_SOFTIRQ
*/
if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
cpu_isset(cpu, nohz.cpu_mask))
return;
#endif
if (time_after_eq(jiffies, rq->next_balance))
raise_softirq(SCHED_SOFTIRQ);
}
#else
/*
* on UP we do not need to balance between CPUs:
*/
static inline void idle_balance(int cpu, struct rq *rq)
{
}
#endif
DEFINE_PER_CPU(struct kernel_stat, kstat);
EXPORT_PER_CPU_SYMBOL(kstat);
/*
* This is called on clock ticks and on context switches.
* Bank in p->sched_time the ns elapsed since the last tick or switch.
*/
static inline void
update_cpu_clock(struct task_struct *p, struct rq *rq, unsigned long long now)
{
p->sched_time += now - p->last_ran;
p->last_ran = rq->most_recent_timestamp = now;
}
/*
* Return current->sched_time plus any more ns on the sched_clock
* that have not yet been banked.
*/
unsigned long long current_sched_time(const struct task_struct *p)
{
unsigned long long ns;
unsigned long flags;
local_irq_save(flags);
ns = p->sched_time + sched_clock() - p->last_ran;
local_irq_restore(flags);
return ns;
}
/*
* We place interactive tasks back into the active array, if possible.
*
* To guarantee that this does not starve expired tasks we ignore the
* interactivity of a task if the first expired task had to wait more
* than a 'reasonable' amount of time. This deadline timeout is
* load-dependent, as the frequency of array switched decreases with
* increasing number of running tasks. We also ignore the interactivity
* if a better static_prio task has expired:
*/
static inline int expired_starving(struct rq *rq)
{
if (rq->curr->static_prio > rq->best_expired_prio)
return 1;
if (!STARVATION_LIMIT || !rq->expired_timestamp)
return 0;
if (jiffies - rq->expired_timestamp > STARVATION_LIMIT * rq->nr_running)
return 1;
return 0;
}
/*
* Account user cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in user space since the last update
*/
void account_user_time(struct task_struct *p, cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp;
p->utime = cputime_add(p->utime, cputime);
/* Add user time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (TASK_NICE(p) > 0)
cpustat->nice = cputime64_add(cpustat->nice, tmp);
else
cpustat->user = cputime64_add(cpustat->user, tmp);
}
/*
* Account system cpu time to a process.
* @p: the process that the cpu time gets accounted to
* @hardirq_offset: the offset to subtract from hardirq_count()
* @cputime: the cpu time spent in kernel space since the last update
*/
void account_system_time(struct task_struct *p, int hardirq_offset,
cputime_t cputime)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
struct rq *rq = this_rq();
cputime64_t tmp;
p->stime = cputime_add(p->stime, cputime);
/* Add system time to cpustat. */
tmp = cputime_to_cputime64(cputime);
if (hardirq_count() - hardirq_offset)
cpustat->irq = cputime64_add(cpustat->irq, tmp);
else if (softirq_count())
cpustat->softirq = cputime64_add(cpustat->softirq, tmp);
else if (p != rq->idle)
cpustat->system = cputime64_add(cpustat->system, tmp);
else if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
/* Account for system time used */
acct_update_integrals(p);
}
/*
* Account for involuntary wait time.
* @p: the process from which the cpu time has been stolen
* @steal: the cpu time spent in involuntary wait
*/
void account_steal_time(struct task_struct *p, cputime_t steal)
{
struct cpu_usage_stat *cpustat = &kstat_this_cpu.cpustat;
cputime64_t tmp = cputime_to_cputime64(steal);
struct rq *rq = this_rq();
if (p == rq->idle) {
p->stime = cputime_add(p->stime, steal);
if (atomic_read(&rq->nr_iowait) > 0)
cpustat->iowait = cputime64_add(cpustat->iowait, tmp);
else
cpustat->idle = cputime64_add(cpustat->idle, tmp);
} else
cpustat->steal = cputime64_add(cpustat->steal, tmp);
}
static void task_running_tick(struct rq *rq, struct task_struct *p)
{
if (p->array != rq->active) {
/* Task has expired but was not scheduled yet */
set_tsk_need_resched(p);
return;
}
spin_lock(&rq->lock);
/*
* The task was running during this tick - update the
* time slice counter. Note: we do not update a thread's
* priority until it either goes to sleep or uses up its
* timeslice. This makes it possible for interactive tasks
* to use up their timeslices at their highest priority levels.
*/
if (rt_task(p)) {
/*
* RR tasks need a special form of timeslice management.
* FIFO tasks have no timeslices.
*/
if ((p->policy == SCHED_RR) && !--p->time_slice) {
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
set_tsk_need_resched(p);
/* put it at the end of the queue: */
requeue_task(p, rq->active);
}
goto out_unlock;
}
if (!--p->time_slice) {
dequeue_task(p, rq->active);
set_tsk_need_resched(p);
p->prio = effective_prio(p);
p->time_slice = task_timeslice(p);
p->first_time_slice = 0;
if (!rq->expired_timestamp)
rq->expired_timestamp = jiffies;
if (!TASK_INTERACTIVE(p) || expired_starving(rq)) {
enqueue_task(p, rq->expired);
if (p->static_prio < rq->best_expired_prio)
rq->best_expired_prio = p->static_prio;
} else
enqueue_task(p, rq->active);
} else {
/*
* Prevent a too long timeslice allowing a task to monopolize
* the CPU. We do this by splitting up the timeslice into
* smaller pieces.
*
* Note: this does not mean the task's timeslices expire or
* get lost in any way, they just might be preempted by
* another task of equal priority. (one with higher
* priority would have preempted this task already.) We
* requeue this task to the end of the list on this priority
* level, which is in essence a round-robin of tasks with
* equal priority.
*
* This only applies to tasks in the interactive
* delta range with at least TIMESLICE_GRANULARITY to requeue.
*/
if (TASK_INTERACTIVE(p) && !((task_timeslice(p) -
p->time_slice) % TIMESLICE_GRANULARITY(p)) &&
(p->time_slice >= TIMESLICE_GRANULARITY(p)) &&
(p->array == rq->active)) {
requeue_task(p, rq->active);
set_tsk_need_resched(p);
}
}
out_unlock:
spin_unlock(&rq->lock);
}
/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
*
* It also gets called by the fork code, when changing the parent's
* timeslices.
*/
void scheduler_tick(void)
{
unsigned long long now = sched_clock();
struct task_struct *p = current;
int cpu = smp_processor_id();
int idle_at_tick = idle_cpu(cpu);
struct rq *rq = cpu_rq(cpu);
update_cpu_clock(p, rq, now);
if (!idle_at_tick)
task_running_tick(rq, p);
#ifdef CONFIG_SMP
update_load(rq);
rq->idle_at_tick = idle_at_tick;
trigger_load_balance(cpu);
#endif
}
#if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
void fastcall add_preempt_count(int val)
{
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
return;
preempt_count() += val;
/*
* Spinlock count overflowing soon?
*/
DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
PREEMPT_MASK - 10);
}
EXPORT_SYMBOL(add_preempt_count);
void fastcall sub_preempt_count(int val)
{
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
return;
/*
* Is the spinlock portion underflowing?
*/
if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
!(preempt_count() & PREEMPT_MASK)))
return;
preempt_count() -= val;
}
EXPORT_SYMBOL(sub_preempt_count);
#endif
static inline int interactive_sleep(enum sleep_type sleep_type)
{
return (sleep_type == SLEEP_INTERACTIVE ||
sleep_type == SLEEP_INTERRUPTED);
}
/*
* schedule() is the main scheduler function.
*/
asmlinkage void __sched schedule(void)
{
struct task_struct *prev, *next;
struct prio_array *array;
struct list_head *queue;
unsigned long long now;
unsigned long run_time;
int cpu, idx, new_prio;
long *switch_count;
struct rq *rq;
/*
* Test if we are atomic. Since do_exit() needs to call into
* schedule() atomically, we ignore that path for now.
* Otherwise, whine if we are scheduling when we should not be.
*/
if (unlikely(in_atomic() && !current->exit_state)) {
printk(KERN_ERR "BUG: scheduling while atomic: "
"%s/0x%08x/%d\n",
current->comm, preempt_count(), current->pid);
debug_show_held_locks(current);
if (irqs_disabled())
print_irqtrace_events(current);
dump_stack();
}
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
need_resched:
preempt_disable();
prev = current;
release_kernel_lock(prev);
need_resched_nonpreemptible:
rq = this_rq();
/*
* The idle thread is not allowed to schedule!
* Remove this check after it has been exercised a bit.
*/
if (unlikely(prev == rq->idle) && prev->state != TASK_RUNNING) {
printk(KERN_ERR "bad: scheduling from the idle thread!\n");
dump_stack();
}
schedstat_inc(rq, sched_cnt);
now = sched_clock();
if (likely((long long)(now - prev->timestamp) < NS_MAX_SLEEP_AVG)) {
run_time = now - prev->timestamp;
if (unlikely((long long)(now - prev->timestamp) < 0))
run_time = 0;
} else
run_time = NS_MAX_SLEEP_AVG;
/*
* Tasks charged proportionately less run_time at high sleep_avg to
* delay them losing their interactive status
*/
run_time /= (CURRENT_BONUS(prev) ? : 1);
spin_lock_irq(&rq->lock);
switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
switch_count = &prev->nvcsw;
if (unlikely((prev->state & TASK_INTERRUPTIBLE) &&
unlikely(signal_pending(prev))))
prev->state = TASK_RUNNING;
else {
if (prev->state == TASK_UNINTERRUPTIBLE)
rq->nr_uninterruptible++;
deactivate_task(prev, rq);
}
}
cpu = smp_processor_id();
if (unlikely(!rq->nr_running)) {
idle_balance(cpu, rq);
if (!rq->nr_running) {
next = rq->idle;
rq->expired_timestamp = 0;
goto switch_tasks;
}
}
array = rq->active;
if (unlikely(!array->nr_active)) {
/*
* Switch the active and expired arrays.
*/
schedstat_inc(rq, sched_switch);
rq->active = rq->expired;
rq->expired = array;
array = rq->active;
rq->expired_timestamp = 0;
rq->best_expired_prio = MAX_PRIO;
}
idx = sched_find_first_bit(array->bitmap);
queue = array->queue + idx;
next = list_entry(queue->next, struct task_struct, run_list);
if (!rt_task(next) && interactive_sleep(next->sleep_type)) {
unsigned long long delta = now - next->timestamp;
if (unlikely((long long)(now - next->timestamp) < 0))
delta = 0;
if (next->sleep_type == SLEEP_INTERACTIVE)
delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
array = next->array;
new_prio = recalc_task_prio(next, next->timestamp + delta);
if (unlikely(next->prio != new_prio)) {
dequeue_task(next, array);
next->prio = new_prio;
enqueue_task(next, array);
}
}
next->sleep_type = SLEEP_NORMAL;
switch_tasks:
if (next == rq->idle)
schedstat_inc(rq, sched_goidle);
prefetch(next);
prefetch_stack(next);
clear_tsk_need_resched(prev);
rcu_qsctr_inc(task_cpu(prev));
update_cpu_clock(prev, rq, now);
prev->sleep_avg -= run_time;
if ((long)prev->sleep_avg <= 0)
prev->sleep_avg = 0;
prev->timestamp = prev->last_ran = now;
sched_info_switch(prev, next);
if (likely(prev != next)) {
next->timestamp = next->last_ran = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
prepare_task_switch(rq, next);
prev = context_switch(rq, prev, next);
barrier();
/*
* this_rq must be evaluated again because prev may have moved
* CPUs since it called schedule(), thus the 'rq' on its stack
* frame will be invalid.
*/
finish_task_switch(this_rq(), prev);
} else
spin_unlock_irq(&rq->lock);
prev = current;
if (unlikely(reacquire_kernel_lock(prev) < 0))
goto need_resched_nonpreemptible;
preempt_enable_no_resched();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(schedule);
#ifdef CONFIG_PREEMPT
/*
* this is the entry point to schedule() from in-kernel preemption
* off of preempt_enable. Kernel preemptions off return from interrupt
* occur there and call schedule directly.
*/
asmlinkage void __sched preempt_schedule(void)
{
struct thread_info *ti = current_thread_info();
#ifdef CONFIG_PREEMPT_BKL
struct task_struct *task = current;
int saved_lock_depth;
#endif
/*
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
if (likely(ti->preempt_count || irqs_disabled()))
return;
need_resched:
add_preempt_count(PREEMPT_ACTIVE);
/*
* We keep the big kernel semaphore locked, but we
* clear ->lock_depth so that schedule() doesnt
* auto-release the semaphore:
*/
#ifdef CONFIG_PREEMPT_BKL
saved_lock_depth = task->lock_depth;
task->lock_depth = -1;
#endif
schedule();
#ifdef CONFIG_PREEMPT_BKL
task->lock_depth = saved_lock_depth;
#endif
sub_preempt_count(PREEMPT_ACTIVE);
/* we could miss a preemption opportunity between schedule and now */
barrier();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
EXPORT_SYMBOL(preempt_schedule);
/*
* this is the entry point to schedule() from kernel preemption
* off of irq context.
* Note, that this is called and return with irqs disabled. This will
* protect us against recursive calling from irq.
*/
asmlinkage void __sched preempt_schedule_irq(void)
{
struct thread_info *ti = current_thread_info();
#ifdef CONFIG_PREEMPT_BKL
struct task_struct *task = current;
int saved_lock_depth;
#endif
/* Catch callers which need to be fixed */
BUG_ON(ti->preempt_count || !irqs_disabled());
need_resched:
add_preempt_count(PREEMPT_ACTIVE);
/*
* We keep the big kernel semaphore locked, but we
* clear ->lock_depth so that schedule() doesnt
* auto-release the semaphore:
*/
#ifdef CONFIG_PREEMPT_BKL
saved_lock_depth = task->lock_depth;
task->lock_depth = -1;
#endif
local_irq_enable();
schedule();
local_irq_disable();
#ifdef CONFIG_PREEMPT_BKL
task->lock_depth = saved_lock_depth;
#endif
sub_preempt_count(PREEMPT_ACTIVE);
/* we could miss a preemption opportunity between schedule and now */
barrier();
if (unlikely(test_thread_flag(TIF_NEED_RESCHED)))
goto need_resched;
}
#endif /* CONFIG_PREEMPT */
int default_wake_function(wait_queue_t *curr, unsigned mode, int sync,
void *key)
{
return try_to_wake_up(curr->private, mode, sync);
}
EXPORT_SYMBOL(default_wake_function);
/*
* The core wakeup function. Non-exclusive wakeups (nr_exclusive == 0) just
* wake everything up. If it's an exclusive wakeup (nr_exclusive == small +ve
* number) then we wake all the non-exclusive tasks and one exclusive task.
*
* There are circumstances in which we can try to wake a task which has already
* started to run but is not in state TASK_RUNNING. try_to_wake_up() returns
* zero in this (rare) case, and we handle it by continuing to scan the queue.
*/
static void __wake_up_common(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, int sync, void *key)
{
struct list_head *tmp, *next;
list_for_each_safe(tmp, next, &q->task_list) {
wait_queue_t *curr = list_entry(tmp, wait_queue_t, task_list);
unsigned flags = curr->flags;
if (curr->func(curr, mode, sync, key) &&
(flags & WQ_FLAG_EXCLUSIVE) && !--nr_exclusive)
break;
}
}
/**
* __wake_up - wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
* @key: is directly passed to the wakeup function
*/
void fastcall __wake_up(wait_queue_head_t *q, unsigned int mode,
int nr_exclusive, void *key)
{
unsigned long flags;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, 0, key);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL(__wake_up);
/*
* Same as __wake_up but called with the spinlock in wait_queue_head_t held.
*/
void fastcall __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
{
__wake_up_common(q, mode, 1, 0, NULL);
}
/**
* __wake_up_sync - wake up threads blocked on a waitqueue.
* @q: the waitqueue
* @mode: which threads
* @nr_exclusive: how many wake-one or wake-many threads to wake up
*
* The sync wakeup differs that the waker knows that it will schedule
* away soon, so while the target thread will be woken up, it will not
* be migrated to another CPU - ie. the two threads are 'synchronized'
* with each other. This can prevent needless bouncing between CPUs.
*
* On UP it can prevent extra preemption.
*/
void fastcall
__wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
{
unsigned long flags;
int sync = 1;
if (unlikely(!q))
return;
if (unlikely(!nr_exclusive))
sync = 0;
spin_lock_irqsave(&q->lock, flags);
__wake_up_common(q, mode, nr_exclusive, sync, NULL);
spin_unlock_irqrestore(&q->lock, flags);
}
EXPORT_SYMBOL_GPL(__wake_up_sync); /* For internal use only */
void fastcall complete(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done++;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
1, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete);
void fastcall complete_all(struct completion *x)
{
unsigned long flags;
spin_lock_irqsave(&x->wait.lock, flags);
x->done += UINT_MAX/2;
__wake_up_common(&x->wait, TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE,
0, 0, NULL);
spin_unlock_irqrestore(&x->wait.lock, flags);
}
EXPORT_SYMBOL(complete_all);
void fastcall __sched wait_for_completion(struct completion *x)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
spin_unlock_irq(&x->wait.lock);
}
EXPORT_SYMBOL(wait_for_completion);
unsigned long fastcall __sched
wait_for_completion_timeout(struct completion *x, unsigned long timeout)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
timeout = schedule_timeout(timeout);
spin_lock_irq(&x->wait.lock);
if (!timeout) {
__remove_wait_queue(&x->wait, &wait);
goto out;
}
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return timeout;
}
EXPORT_SYMBOL(wait_for_completion_timeout);
int fastcall __sched wait_for_completion_interruptible(struct completion *x)
{
int ret = 0;
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
if (signal_pending(current)) {
ret = -ERESTARTSYS;
__remove_wait_queue(&x->wait, &wait);
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
schedule();
spin_lock_irq(&x->wait.lock);
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return ret;
}
EXPORT_SYMBOL(wait_for_completion_interruptible);
unsigned long fastcall __sched
wait_for_completion_interruptible_timeout(struct completion *x,
unsigned long timeout)
{
might_sleep();
spin_lock_irq(&x->wait.lock);
if (!x->done) {
DECLARE_WAITQUEUE(wait, current);
wait.flags |= WQ_FLAG_EXCLUSIVE;
__add_wait_queue_tail(&x->wait, &wait);
do {
if (signal_pending(current)) {
timeout = -ERESTARTSYS;
__remove_wait_queue(&x->wait, &wait);
goto out;
}
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&x->wait.lock);
timeout = schedule_timeout(timeout);
spin_lock_irq(&x->wait.lock);
if (!timeout) {
__remove_wait_queue(&x->wait, &wait);
goto out;
}
} while (!x->done);
__remove_wait_queue(&x->wait, &wait);
}
x->done--;
out:
spin_unlock_irq(&x->wait.lock);
return timeout;
}
EXPORT_SYMBOL(wait_for_completion_interruptible_timeout);
#define SLEEP_ON_VAR \
unsigned long flags; \
wait_queue_t wait; \
init_waitqueue_entry(&wait, current);
#define SLEEP_ON_HEAD \
spin_lock_irqsave(&q->lock,flags); \
__add_wait_queue(q, &wait); \
spin_unlock(&q->lock);
#define SLEEP_ON_TAIL \
spin_lock_irq(&q->lock); \
__remove_wait_queue(q, &wait); \
spin_unlock_irqrestore(&q->lock, flags);
void fastcall __sched interruptible_sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(interruptible_sleep_on);
long fastcall __sched
interruptible_sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
SLEEP_ON_VAR
current->state = TASK_INTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(interruptible_sleep_on_timeout);
void fastcall __sched sleep_on(wait_queue_head_t *q)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
schedule();
SLEEP_ON_TAIL
}
EXPORT_SYMBOL(sleep_on);
long fastcall __sched sleep_on_timeout(wait_queue_head_t *q, long timeout)
{
SLEEP_ON_VAR
current->state = TASK_UNINTERRUPTIBLE;
SLEEP_ON_HEAD
timeout = schedule_timeout(timeout);
SLEEP_ON_TAIL
return timeout;
}
EXPORT_SYMBOL(sleep_on_timeout);
#ifdef CONFIG_RT_MUTEXES
/*
* rt_mutex_setprio - set the current priority of a task
* @p: task
* @prio: prio value (kernel-internal form)
*
* This function changes the 'effective' priority of a task. It does
* not touch ->normal_prio like __setscheduler().
*
* Used by the rt_mutex code to implement priority inheritance logic.
*/
void rt_mutex_setprio(struct task_struct *p, int prio)
{
struct prio_array *array;
unsigned long flags;
struct rq *rq;
int oldprio;
BUG_ON(prio < 0 || prio > MAX_PRIO);
rq = task_rq_lock(p, &flags);
oldprio = p->prio;
array = p->array;
if (array)
dequeue_task(p, array);
p->prio = prio;
if (array) {
/*
* If changing to an RT priority then queue it
* in the active array!
*/
if (rt_task(p))
array = rq->active;
enqueue_task(p, array);
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
} else if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
task_rq_unlock(rq, &flags);
}
#endif
void set_user_nice(struct task_struct *p, long nice)
{
struct prio_array *array;
int old_prio, delta;
unsigned long flags;
struct rq *rq;
if (TASK_NICE(p) == nice || nice < -20 || nice > 19)
return;
/*
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
rq = task_rq_lock(p, &flags);
/*
* The RT priorities are set via sched_setscheduler(), but we still
* allow the 'normal' nice value to be set - but as expected
* it wont have any effect on scheduling until the task is
* not SCHED_NORMAL/SCHED_BATCH:
*/
if (has_rt_policy(p)) {
p->static_prio = NICE_TO_PRIO(nice);
goto out_unlock;
}
array = p->array;
if (array) {
dequeue_task(p, array);
dec_raw_weighted_load(rq, p);
}
p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p);
old_prio = p->prio;
p->prio = effective_prio(p);
delta = p->prio - old_prio;
if (array) {
enqueue_task(p, array);
inc_raw_weighted_load(rq, p);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
*/
if (delta < 0 || (delta > 0 && task_running(rq, p)))
resched_task(rq->curr);
}
out_unlock:
task_rq_unlock(rq, &flags);
}
EXPORT_SYMBOL(set_user_nice);
/*
* can_nice - check if a task can reduce its nice value
* @p: task
* @nice: nice value
*/
int can_nice(const struct task_struct *p, const int nice)
{
/* convert nice value [19,-20] to rlimit style value [1,40] */
int nice_rlim = 20 - nice;
return (nice_rlim <= p->signal->rlim[RLIMIT_NICE].rlim_cur ||
capable(CAP_SYS_NICE));
}
#ifdef __ARCH_WANT_SYS_NICE
/*
* sys_nice - change the priority of the current process.
* @increment: priority increment
*
* sys_setpriority is a more generic, but much slower function that
* does similar things.
*/
asmlinkage long sys_nice(int increment)
{
long nice, retval;
/*
* Setpriority might change our priority at the same moment.
* We don't have to worry. Conceptually one call occurs first
* and we have a single winner.
*/
if (increment < -40)
increment = -40;
if (increment > 40)
increment = 40;
nice = PRIO_TO_NICE(current->static_prio) + increment;
if (nice < -20)
nice = -20;
if (nice > 19)
nice = 19;
if (increment < 0 && !can_nice(current, nice))
return -EPERM;
retval = security_task_setnice(current, nice);
if (retval)
return retval;
set_user_nice(current, nice);
return 0;
}
#endif
/**
* task_prio - return the priority value of a given task.
* @p: the task in question.
*
* This is the priority value as seen by users in /proc.
* RT tasks are offset by -200. Normal tasks are centered
* around 0, value goes from -16 to +15.
*/
int task_prio(const struct task_struct *p)
{
return p->prio - MAX_RT_PRIO;
}
/**
* task_nice - return the nice value of a given task.
* @p: the task in question.
*/
int task_nice(const struct task_struct *p)
{
return TASK_NICE(p);
}
EXPORT_SYMBOL_GPL(task_nice);
/**
* idle_cpu - is a given cpu idle currently?
* @cpu: the processor in question.
*/
int idle_cpu(int cpu)
{
return cpu_curr(cpu) == cpu_rq(cpu)->idle;
}
/**
* idle_task - return the idle task for a given cpu.
* @cpu: the processor in question.
*/
struct task_struct *idle_task(int cpu)
{
return cpu_rq(cpu)->idle;
}
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
*/
static inline struct task_struct *find_process_by_pid(pid_t pid)
{
return pid ? find_task_by_pid(pid) : current;
}
/* Actually do priority change: must hold rq lock. */
static void __setscheduler(struct task_struct *p, int policy, int prio)
{
BUG_ON(p->array);
p->policy = policy;
p->rt_priority = prio;
p->normal_prio = normal_prio(p);
/* we are holding p->pi_lock already */
p->prio = rt_mutex_getprio(p);
/*
* SCHED_BATCH tasks are treated as perpetual CPU hogs:
*/
if (policy == SCHED_BATCH)
p->sleep_avg = 0;
set_load_weight(p);
}
/**
* sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* NOTE that the task may be already dead.
*/
int sched_setscheduler(struct task_struct *p, int policy,
struct sched_param *param)
{
int retval, oldprio, oldpolicy = -1;
struct prio_array *array;
unsigned long flags;
struct rq *rq;
/* may grab non-irq protected spin_locks */
BUG_ON(in_interrupt());
recheck:
/* double check policy once rq lock held */
if (policy < 0)
policy = oldpolicy = p->policy;
else if (policy != SCHED_FIFO && policy != SCHED_RR &&
policy != SCHED_NORMAL && policy != SCHED_BATCH)
return -EINVAL;
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL and
* SCHED_BATCH is 0.
*/
if (param->sched_priority < 0 ||
(p->mm && param->sched_priority > MAX_USER_RT_PRIO-1) ||
(!p->mm && param->sched_priority > MAX_RT_PRIO-1))
return -EINVAL;
if (is_rt_policy(policy) != (param->sched_priority != 0))
return -EINVAL;
/*
* Allow unprivileged RT tasks to decrease priority:
*/
if (!capable(CAP_SYS_NICE)) {
if (is_rt_policy(policy)) {
unsigned long rlim_rtprio;
unsigned long flags;
if (!lock_task_sighand(p, &flags))
return -ESRCH;
rlim_rtprio = p->signal->rlim[RLIMIT_RTPRIO].rlim_cur;
unlock_task_sighand(p, &flags);
/* can't set/change the rt policy */
if (policy != p->policy && !rlim_rtprio)
return -EPERM;
/* can't increase priority */
if (param->sched_priority > p->rt_priority &&
param->sched_priority > rlim_rtprio)
return -EPERM;
}
/* can't change other user's priorities */
if ((current->euid != p->euid) &&
(current->euid != p->uid))
return -EPERM;
}
retval = security_task_setscheduler(p, policy, param);
if (retval)
return retval;
/*
* make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
*/
spin_lock_irqsave(&p->pi_lock, flags);
/*
* To be able to change p->policy safely, the apropriate
* runqueue lock must be held.
*/
rq = __task_rq_lock(p);
/* recheck policy now with rq lock held */
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
goto recheck;
}
array = p->array;
if (array)
deactivate_task(p, rq);
oldprio = p->prio;
__setscheduler(p, policy, param->sched_priority);
if (array) {
__activate_task(p, rq);
/*
* Reschedule if we are currently running on this runqueue and
* our priority decreased, or if we are not currently running on
* this runqueue and our priority is higher than the current's
*/
if (task_running(rq, p)) {
if (p->prio > oldprio)
resched_task(rq->curr);
} else if (TASK_PREEMPTS_CURR(p, rq))
resched_task(rq->curr);
}
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
rt_mutex_adjust_pi(p);
return 0;
}
EXPORT_SYMBOL_GPL(sched_setscheduler);
static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lparam;
struct task_struct *p;
int retval;
if (!param || pid < 0)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
if (p != NULL)
retval = sched_setscheduler(p, policy, &lparam);
rcu_read_unlock();
return retval;
}
/**
* sys_sched_setscheduler - set/change the scheduler policy and RT priority
* @pid: the pid in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setscheduler(pid_t pid, int policy,
struct sched_param __user *param)
{
/* negative values for policy are not valid */
if (policy < 0)
return -EINVAL;
return do_sched_setscheduler(pid, policy, param);
}
/**
* sys_sched_setparam - set/change the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the new RT priority.
*/
asmlinkage long sys_sched_setparam(pid_t pid, struct sched_param __user *param)
{
return do_sched_setscheduler(pid, -1, param);
}
/**
* sys_sched_getscheduler - get the policy (scheduling class) of a thread
* @pid: the pid in question.
*/
asmlinkage long sys_sched_getscheduler(pid_t pid)
{
struct task_struct *p;
int retval = -EINVAL;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (p) {
retval = security_task_getscheduler(p);
if (!retval)
retval = p->policy;
}
read_unlock(&tasklist_lock);
out_nounlock:
return retval;
}
/**
* sys_sched_getscheduler - get the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the RT priority.
*/
asmlinkage long sys_sched_getparam(pid_t pid, struct sched_param __user *param)
{
struct sched_param lp;
struct task_struct *p;
int retval = -EINVAL;
if (!param || pid < 0)
goto out_nounlock;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
lp.sched_priority = p->rt_priority;
read_unlock(&tasklist_lock);
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
long sched_setaffinity(pid_t pid, cpumask_t new_mask)
{
cpumask_t cpus_allowed;
struct task_struct *p;
int retval;
mutex_lock(&sched_hotcpu_mutex);
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
mutex_unlock(&sched_hotcpu_mutex);
return -ESRCH;
}
/*
* It is not safe to call set_cpus_allowed with the
* tasklist_lock held. We will bump the task_struct's
* usage count and then drop tasklist_lock.
*/
get_task_struct(p);
read_unlock(&tasklist_lock);
retval = -EPERM;
if ((current->euid != p->euid) && (current->euid != p->uid) &&
!capable(CAP_SYS_NICE))
goto out_unlock;
retval = security_task_setscheduler(p, 0, NULL);
if (retval)
goto out_unlock;
cpus_allowed = cpuset_cpus_allowed(p);
cpus_and(new_mask, new_mask, cpus_allowed);
retval = set_cpus_allowed(p, new_mask);
out_unlock:
put_task_struct(p);
mutex_unlock(&sched_hotcpu_mutex);
return retval;
}
static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
cpumask_t *new_mask)
{
if (len < sizeof(cpumask_t)) {
memset(new_mask, 0, sizeof(cpumask_t));
} else if (len > sizeof(cpumask_t)) {
len = sizeof(cpumask_t);
}
return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}
/**
* sys_sched_setaffinity - set the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to the new cpu mask
*/
asmlinkage long sys_sched_setaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
cpumask_t new_mask;
int retval;
retval = get_user_cpu_mask(user_mask_ptr, len, &new_mask);
if (retval)
return retval;
return sched_setaffinity(pid, new_mask);
}
/*
* Represents all cpu's present in the system
* In systems capable of hotplug, this map could dynamically grow
* as new cpu's are detected in the system via any platform specific
* method, such as ACPI for e.g.
*/
cpumask_t cpu_present_map __read_mostly;
EXPORT_SYMBOL(cpu_present_map);
#ifndef CONFIG_SMP
cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_online_map);
cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
EXPORT_SYMBOL(cpu_possible_map);
#endif
long sched_getaffinity(pid_t pid, cpumask_t *mask)
{
struct task_struct *p;
int retval;
mutex_lock(&sched_hotcpu_mutex);
read_lock(&tasklist_lock);
retval = -ESRCH;
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
cpus_and(*mask, p->cpus_allowed, cpu_online_map);
out_unlock:
read_unlock(&tasklist_lock);
mutex_unlock(&sched_hotcpu_mutex);
if (retval)
return retval;
return 0;
}
/**
* sys_sched_getaffinity - get the cpu affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to hold the current cpu mask
*/
asmlinkage long sys_sched_getaffinity(pid_t pid, unsigned int len,
unsigned long __user *user_mask_ptr)
{
int ret;
cpumask_t mask;
if (len < sizeof(cpumask_t))
return -EINVAL;
ret = sched_getaffinity(pid, &mask);
if (ret < 0)
return ret;
if (copy_to_user(user_mask_ptr, &mask, sizeof(cpumask_t)))
return -EFAULT;
return sizeof(cpumask_t);
}
/**
* sys_sched_yield - yield the current processor to other threads.
*
* This function yields the current CPU by moving the calling thread
* to the expired array. If there are no other threads running on this
* CPU then this function will return.
*/
asmlinkage long sys_sched_yield(void)
{
struct rq *rq = this_rq_lock();
struct prio_array *array = current->array, *target = rq->expired;
schedstat_inc(rq, yld_cnt);
/*
* We implement yielding by moving the task into the expired
* queue.
*
* (special rule: RT tasks will just roundrobin in the active
* array.)
*/
if (rt_task(current))
target = rq->active;
if (array->nr_active == 1) {
schedstat_inc(rq, yld_act_empty);
if (!rq->expired->nr_active)
schedstat_inc(rq, yld_both_empty);
} else if (!rq->expired->nr_active)
schedstat_inc(rq, yld_exp_empty);
if (array != target) {
dequeue_task(current, array);
enqueue_task(current, target);
} else
/*
* requeue_task is cheaper so perform that if possible.
*/
requeue_task(current, array);
/*
* Since we are going to call schedule() anyway, there's
* no need to preempt or enable interrupts:
*/
__release(rq->lock);
spin_release(&rq->lock.dep_map, 1, _THIS_IP_);
_raw_spin_unlock(&rq->lock);
preempt_enable_no_resched();
schedule();
return 0;
}
static void __cond_resched(void)
{
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
__might_sleep(__FILE__, __LINE__);
#endif
/*
* The BKS might be reacquired before we have dropped
* PREEMPT_ACTIVE, which could trigger a second
* cond_resched() call.
*/
do {
add_preempt_count(PREEMPT_ACTIVE);
schedule();
sub_preempt_count(PREEMPT_ACTIVE);
} while (need_resched());
}
int __sched cond_resched(void)
{
if (need_resched() && !(preempt_count() & PREEMPT_ACTIVE) &&
system_state == SYSTEM_RUNNING) {
__cond_resched();
return 1;
}
return 0;
}
EXPORT_SYMBOL(cond_resched);
/*
* cond_resched_lock() - if a reschedule is pending, drop the given lock,
* call schedule, and on return reacquire the lock.
*
* This works OK both with and without CONFIG_PREEMPT. We do strange low-level
* operations here to prevent schedule() from being called twice (once via
* spin_unlock(), once by hand).
*/
int cond_resched_lock(spinlock_t *lock)
{
int ret = 0;
if (need_lockbreak(lock)) {
spin_unlock(lock);
cpu_relax();
ret = 1;
spin_lock(lock);
}
if (need_resched() && system_state == SYSTEM_RUNNING) {
spin_release(&lock->dep_map, 1, _THIS_IP_);
_raw_spin_unlock(lock);
preempt_enable_no_resched();
__cond_resched();
ret = 1;
spin_lock(lock);
}
return ret;
}
EXPORT_SYMBOL(cond_resched_lock);
int __sched cond_resched_softirq(void)
{
BUG_ON(!in_softirq());
if (need_resched() && system_state == SYSTEM_RUNNING) {
local_bh_enable();
__cond_resched();
local_bh_disable();
return 1;
}
return 0;
}
EXPORT_SYMBOL(cond_resched_softirq);
/**
* yield - yield the current processor to other threads.
*
* This is a shortcut for kernel-space yielding - it marks the
* thread runnable and calls sys_sched_yield().
*/
void __sched yield(void)
{
set_current_state(TASK_RUNNING);
sys_sched_yield();
}
EXPORT_SYMBOL(yield);
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
*
* But don't do that if it is a deliberate, throttling IO wait (this task
* has set its backing_dev_info: the queue against which it should throttle)
*/
void __sched io_schedule(void)
{
struct rq *rq = &__raw_get_cpu_var(runqueues);
delayacct_blkio_start();
atomic_inc(&rq->nr_iowait);
schedule();
atomic_dec(&rq->nr_iowait);
delayacct_blkio_end();
}
EXPORT_SYMBOL(io_schedule);
long __sched io_schedule_timeout(long timeout)
{
struct rq *rq = &__raw_get_cpu_var(runqueues);
long ret;
delayacct_blkio_start();
atomic_inc(&rq->nr_iowait);
ret = schedule_timeout(timeout);
atomic_dec(&rq->nr_iowait);
delayacct_blkio_end();
return ret;
}
/**
* sys_sched_get_priority_max - return maximum RT priority.
* @policy: scheduling class.
*
* this syscall returns the maximum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_max(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = MAX_USER_RT_PRIO-1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
ret = 0;
break;
}
return ret;
}
/**
* sys_sched_get_priority_min - return minimum RT priority.
* @policy: scheduling class.
*
* this syscall returns the minimum rt_priority that can be used
* by a given scheduling class.
*/
asmlinkage long sys_sched_get_priority_min(int policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = 1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
ret = 0;
}
return ret;
}
/**
* sys_sched_rr_get_interval - return the default timeslice of a process.
* @pid: pid of the process.
* @interval: userspace pointer to the timeslice value.
*
* this syscall writes the default timeslice value of a given process
* into the user-space timespec buffer. A value of '0' means infinity.
*/
asmlinkage
long sys_sched_rr_get_interval(pid_t pid, struct timespec __user *interval)
{
struct task_struct *p;
int retval = -EINVAL;
struct timespec t;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
jiffies_to_timespec(p->policy == SCHED_FIFO ?
0 : task_timeslice(p), &t);
read_unlock(&tasklist_lock);
retval = copy_to_user(interval, &t, sizeof(t)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
read_unlock(&tasklist_lock);
return retval;
}
static const char stat_nam[] = "RSDTtZX";
static void show_task(struct task_struct *p)
{
unsigned long free = 0;
unsigned state;
state = p->state ? __ffs(p->state) + 1 : 0;
printk("%-13.13s %c", p->comm,
state < sizeof(stat_nam) - 1 ? stat_nam[state] : '?');
#if (BITS_PER_LONG == 32)
if (state == TASK_RUNNING)
printk(" running ");
else
printk(" %08lX ", thread_saved_pc(p));
#else
if (state == TASK_RUNNING)
printk(" running task ");
else
printk(" %016lx ", thread_saved_pc(p));
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
{
unsigned long *n = end_of_stack(p);
while (!*n)
n++;
free = (unsigned long)n - (unsigned long)end_of_stack(p);
}
#endif
printk("%5lu %5d %6d", free, p->pid, p->parent->pid);
if (!p->mm)
printk(" (L-TLB)\n");
else
printk(" (NOTLB)\n");
if (state != TASK_RUNNING)
show_stack(p, NULL);
}
void show_state_filter(unsigned long state_filter)
{
struct task_struct *g, *p;
#if (BITS_PER_LONG == 32)
printk("\n"
" free sibling\n");
printk(" task PC stack pid father child younger older\n");
#else
printk("\n"
" free sibling\n");
printk(" task PC stack pid father child younger older\n");
#endif
read_lock(&tasklist_lock);
do_each_thread(g, p) {
/*
* reset the NMI-timeout, listing all files on a slow
* console might take alot of time:
*/
touch_nmi_watchdog();
if (!state_filter || (p->state & state_filter))
show_task(p);
} while_each_thread(g, p);
touch_all_softlockup_watchdogs();
read_unlock(&tasklist_lock);
/*
* Only show locks if all tasks are dumped:
*/
if (state_filter == -1)
debug_show_all_locks();
}
/**
* init_idle - set up an idle thread for a given CPU
* @idle: task in question
* @cpu: cpu the idle task belongs to
*
* NOTE: this function does not set the idle thread's NEED_RESCHED
* flag, to make booting more robust.
*/
void __cpuinit init_idle(struct task_struct *idle, int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
idle->timestamp = sched_clock();
idle->sleep_avg = 0;
idle->array = NULL;
idle->prio = idle->normal_prio = MAX_PRIO;
idle->state = TASK_RUNNING;
idle->cpus_allowed = cpumask_of_cpu(cpu);
set_task_cpu(idle, cpu);
spin_lock_irqsave(&rq->lock, flags);
rq->curr = rq->idle = idle;
#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
idle->oncpu = 1;
#endif
spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
#if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)
task_thread_info(idle)->preempt_count = (idle->lock_depth >= 0);
#else
task_thread_info(idle)->preempt_count = 0;
#endif
}
/*
* In a system that switches off the HZ timer nohz_cpu_mask
* indicates which cpus entered this state. This is used
* in the rcu update to wait only for active cpus. For system
* which do not switch off the HZ timer nohz_cpu_mask should
* always be CPU_MASK_NONE.
*/
cpumask_t nohz_cpu_mask = CPU_MASK_NONE;
#ifdef CONFIG_SMP
/*
* This is how migration works:
*
* 1) we queue a struct migration_req structure in the source CPU's
* runqueue and wake up that CPU's migration thread.
* 2) we down() the locked semaphore => thread blocks.
* 3) migration thread wakes up (implicitly it forces the migrated
* thread off the CPU)
* 4) it gets the migration request and checks whether the migrated
* task is still in the wrong runqueue.
* 5) if it's in the wrong runqueue then the migration thread removes
* it and puts it into the right queue.
* 6) migration thread up()s the semaphore.
* 7) we wake up and the migration is done.
*/
/*
* Change a given task's CPU affinity. Migrate the thread to a
* proper CPU and schedule it away if the CPU it's executing on
* is removed from the allowed bitmask.
*
* NOTE: the caller must have a valid reference to the task, the
* task must not exit() & deallocate itself prematurely. The
* call is not atomic; no spinlocks may be held.
*/
int set_cpus_allowed(struct task_struct *p, cpumask_t new_mask)
{
struct migration_req req;
unsigned long flags;
struct rq *rq;
int ret = 0;
rq = task_rq_lock(p, &flags);
if (!cpus_intersects(new_mask, cpu_online_map)) {
ret = -EINVAL;
goto out;
}
p->cpus_allowed = new_mask;
/* Can the task run on the task's current CPU? If so, we're done */
if (cpu_isset(task_cpu(p), new_mask))
goto out;
if (migrate_task(p, any_online_cpu(new_mask), &req)) {
/* Need help from migration thread: drop lock and wait. */
task_rq_unlock(rq, &flags);
wake_up_process(rq->migration_thread);
wait_for_completion(&req.done);
tlb_migrate_finish(p->mm);
return 0;
}
out:
task_rq_unlock(rq, &flags);
return ret;
}
EXPORT_SYMBOL_GPL(set_cpus_allowed);
/*
* Move (not current) task off this cpu, onto dest cpu. We're doing
* this because either it can't run here any more (set_cpus_allowed()
* away from this CPU, or CPU going down), or because we're
* attempting to rebalance this task on exec (sched_exec).
*
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*
* Returns non-zero if task was successfully migrated.
*/
static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu)
{
struct rq *rq_dest, *rq_src;
int ret = 0;
if (unlikely(cpu_is_offline(dest_cpu)))
return ret;
rq_src = cpu_rq(src_cpu);
rq_dest = cpu_rq(dest_cpu);
double_rq_lock(rq_src, rq_dest);
/* Already moved. */
if (task_cpu(p) != src_cpu)
goto out;
/* Affinity changed (again). */
if (!cpu_isset(dest_cpu, p->cpus_allowed))
goto out;
set_task_cpu(p, dest_cpu);
if (p->array) {
/*
* Sync timestamp with rq_dest's before activating.
* The same thing could be achieved by doing this step
* afterwards, and pretending it was a local activate.
* This way is cleaner and logically correct.
*/
p->timestamp = p->timestamp - rq_src->most_recent_timestamp
+ rq_dest->most_recent_timestamp;
deactivate_task(p, rq_src);
__activate_task(p, rq_dest);
if (TASK_PREEMPTS_CURR(p, rq_dest))
resched_task(rq_dest->curr);
}
ret = 1;
out:
double_rq_unlock(rq_src, rq_dest);
return ret;
}
/*
* migration_thread - this is a highprio system thread that performs
* thread migration by bumping thread off CPU then 'pushing' onto
* another runqueue.
*/
static int migration_thread(void *data)
{
int cpu = (long)data;
struct rq *rq;
rq = cpu_rq(cpu);
BUG_ON(rq->migration_thread != current);
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
struct migration_req *req;
struct list_head *head;
try_to_freeze();
spin_lock_irq(&rq->lock);
if (cpu_is_offline(cpu)) {
spin_unlock_irq(&rq->lock);
goto wait_to_die;
}
if (rq->active_balance) {
active_load_balance(rq, cpu);
rq->active_balance = 0;
}
head = &rq->migration_queue;
if (list_empty(head)) {
spin_unlock_irq(&rq->lock);
schedule();
set_current_state(TASK_INTERRUPTIBLE);
continue;
}
req = list_entry(head->next, struct migration_req, list);
list_del_init(head->next);
spin_unlock(&rq->lock);
__migrate_task(req->task, cpu, req->dest_cpu);
local_irq_enable();
complete(&req->done);
}
__set_current_state(TASK_RUNNING);
return 0;
wait_to_die:
/* Wait for kthread_stop */
set_current_state(TASK_INTERRUPTIBLE);
while (!kthread_should_stop()) {
schedule();
set_current_state(TASK_INTERRUPTIBLE);
}
__set_current_state(TASK_RUNNING);
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Figure out where task on dead CPU should go, use force if neccessary.
* NOTE: interrupts should be disabled by the caller
*/
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
{
unsigned long flags;
cpumask_t mask;
struct rq *rq;
int dest_cpu;
restart:
/* On same node? */
mask = node_to_cpumask(cpu_to_node(dead_cpu));
cpus_and(mask, mask, p->cpus_allowed);
dest_cpu = any_online_cpu(mask);
/* On any allowed CPU? */
if (dest_cpu == NR_CPUS)
dest_cpu = any_online_cpu(p->cpus_allowed);
/* No more Mr. Nice Guy. */
if (dest_cpu == NR_CPUS) {
rq = task_rq_lock(p, &flags);
cpus_setall(p->cpus_allowed);
dest_cpu = any_online_cpu(p->cpus_allowed);
task_rq_unlock(rq, &flags);
/*
* Don't tell them about moving exiting tasks or
* kernel threads (both mm NULL), since they never
* leave kernel.
*/
if (p->mm && printk_ratelimit())
printk(KERN_INFO "process %d (%s) no "
"longer affine to cpu%d\n",
p->pid, p->comm, dead_cpu);
}
if (!__migrate_task(p, dead_cpu, dest_cpu))
goto restart;
}
/*
* While a dead CPU has no uninterruptible tasks queued at this point,
* it might still have a nonzero ->nr_uninterruptible counter, because
* for performance reasons the counter is not stricly tracking tasks to
* their home CPUs. So we just add the counter to another CPU's counter,
* to keep the global sum constant after CPU-down:
*/
static void migrate_nr_uninterruptible(struct rq *rq_src)
{
struct rq *rq_dest = cpu_rq(any_online_cpu(CPU_MASK_ALL));
unsigned long flags;
local_irq_save(flags);
double_rq_lock(rq_src, rq_dest);
rq_dest->nr_uninterruptible += rq_src->nr_uninterruptible;
rq_src->nr_uninterruptible = 0;
double_rq_unlock(rq_src, rq_dest);
local_irq_restore(flags);
}
/* Run through task list and migrate tasks from the dead cpu. */
static void migrate_live_tasks(int src_cpu)
{
struct task_struct *p, *t;
write_lock_irq(&tasklist_lock);
do_each_thread(t, p) {
if (p == current)
continue;
if (task_cpu(p) == src_cpu)
move_task_off_dead_cpu(src_cpu, p);
} while_each_thread(t, p);
write_unlock_irq(&tasklist_lock);
}
/* Schedules idle task to be the next runnable task on current CPU.
* It does so by boosting its priority to highest possible and adding it to
* the _front_ of the runqueue. Used by CPU offline code.
*/
void sched_idle_next(void)
{
int this_cpu = smp_processor_id();
struct rq *rq = cpu_rq(this_cpu);
struct task_struct *p = rq->idle;
unsigned long flags;
/* cpu has to be offline */
BUG_ON(cpu_online(this_cpu));
/*
* Strictly not necessary since rest of the CPUs are stopped by now
* and interrupts disabled on the current cpu.
*/
spin_lock_irqsave(&rq->lock, flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
/* Add idle task to the _front_ of its priority queue: */
__activate_idle_task(p, rq);
spin_unlock_irqrestore(&rq->lock, flags);
}
/*
* Ensures that the idle task is using init_mm right before its cpu goes
* offline.
*/
void idle_task_exit(void)
{
struct mm_struct *mm = current->active_mm;
BUG_ON(cpu_online(smp_processor_id()));
if (mm != &init_mm)
switch_mm(mm, &init_mm, current);
mmdrop(mm);
}
/* called under rq->lock with disabled interrupts */
static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(dead_cpu);
/* Must be exiting, otherwise would be on tasklist. */
BUG_ON(p->exit_state != EXIT_ZOMBIE && p->exit_state != EXIT_DEAD);
/* Cannot have done final schedule yet: would have vanished. */
BUG_ON(p->state == TASK_DEAD);
get_task_struct(p);
/*
* Drop lock around migration; if someone else moves it,
* that's OK. No task can be added to this CPU, so iteration is
* fine.
* NOTE: interrupts should be left disabled --dev@
*/
spin_unlock(&rq->lock);
move_task_off_dead_cpu(dead_cpu, p);
spin_lock(&rq->lock);
put_task_struct(p);
}
/* release_task() removes task from tasklist, so we won't find dead tasks. */
static void migrate_dead_tasks(unsigned int dead_cpu)
{
struct rq *rq = cpu_rq(dead_cpu);
unsigned int arr, i;
for (arr = 0; arr < 2; arr++) {
for (i = 0; i < MAX_PRIO; i++) {
struct list_head *list = &rq->arrays[arr].queue[i];
while (!list_empty(list))
migrate_dead(dead_cpu, list_entry(list->next,
struct task_struct, run_list));
}
}
}
#endif /* CONFIG_HOTPLUG_CPU */
/*
* migration_call - callback that gets triggered when a CPU is added.
* Here we can start up the necessary migration thread for the new CPU.
*/
static int __cpuinit
migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
{
struct task_struct *p;
int cpu = (long)hcpu;
unsigned long flags;
struct rq *rq;
switch (action) {
case CPU_LOCK_ACQUIRE:
mutex_lock(&sched_hotcpu_mutex);
break;
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
if (IS_ERR(p))
return NOTIFY_BAD;
p->flags |= PF_NOFREEZE;
kthread_bind(p, cpu);
/* Must be high prio: stop_machine expects to yield to it. */
rq = task_rq_lock(p, &flags);
__setscheduler(p, SCHED_FIFO, MAX_RT_PRIO-1);
task_rq_unlock(rq, &flags);
cpu_rq(cpu)->migration_thread = p;
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
/* Strictly unneccessary, as first user will wake it. */
wake_up_process(cpu_rq(cpu)->migration_thread);
break;
#ifdef CONFIG_HOTPLUG_CPU
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
if (!cpu_rq(cpu)->migration_thread)
break;
/* Unbind it from offline cpu so it can run. Fall thru. */
kthread_bind(cpu_rq(cpu)->migration_thread,
any_online_cpu(cpu_online_map));
kthread_stop(cpu_rq(cpu)->migration_thread);
cpu_rq(cpu)->migration_thread = NULL;
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
migrate_live_tasks(cpu);
rq = cpu_rq(cpu);
kthread_stop(rq->migration_thread);
rq->migration_thread = NULL;
/* Idle task back to normal (off runqueue, low prio) */
rq = task_rq_lock(rq->idle, &flags);
deactivate_task(rq->idle, rq);
rq->idle->static_prio = MAX_PRIO;
__setscheduler(rq->idle, SCHED_NORMAL, 0);
migrate_dead_tasks(cpu);
task_rq_unlock(rq, &flags);
migrate_nr_uninterruptible(rq);
BUG_ON(rq->nr_running != 0);
/* No need to migrate the tasks: it was best-effort if
* they didn't take sched_hotcpu_mutex. Just wake up
* the requestors. */
spin_lock_irq(&rq->lock);
while (!list_empty(&rq->migration_queue)) {
struct migration_req *req;
req = list_entry(rq->migration_queue.next,
struct migration_req, list);
list_del_init(&req->list);
complete(&req->done);
}
spin_unlock_irq(&rq->lock);
break;
#endif
case CPU_LOCK_RELEASE:
mutex_unlock(&sched_hotcpu_mutex);
break;
}
return NOTIFY_OK;
}
/* Register at highest priority so that task migration (migrate_all_tasks)
* happens before everything else.
*/
static struct notifier_block __cpuinitdata migration_notifier = {
.notifier_call = migration_call,
.priority = 10
};
int __init migration_init(void)
{
void *cpu = (void *)(long)smp_processor_id();
int err;
/* Start one for the boot CPU: */
err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
BUG_ON(err == NOTIFY_BAD);
migration_call(&migration_notifier, CPU_ONLINE, cpu);
register_cpu_notifier(&migration_notifier);
return 0;
}
#endif
#ifdef CONFIG_SMP
/* Number of possible processor ids */
int nr_cpu_ids __read_mostly = NR_CPUS;
EXPORT_SYMBOL(nr_cpu_ids);
#undef SCHED_DOMAIN_DEBUG
#ifdef SCHED_DOMAIN_DEBUG
static void sched_domain_debug(struct sched_domain *sd, int cpu)
{
int level = 0;
if (!sd) {
printk(KERN_DEBUG "CPU%d attaching NULL sched-domain.\n", cpu);
return;
}
printk(KERN_DEBUG "CPU%d attaching sched-domain:\n", cpu);
do {
int i;
char str[NR_CPUS];
struct sched_group *group = sd->groups;
cpumask_t groupmask;
cpumask_scnprintf(str, NR_CPUS, sd->span);
cpus_clear(groupmask);
printk(KERN_DEBUG);
for (i = 0; i < level + 1; i++)
printk(" ");
printk("domain %d: ", level);
if (!(sd->flags & SD_LOAD_BALANCE)) {
printk("does not load-balance\n");
if (sd->parent)
printk(KERN_ERR "ERROR: !SD_LOAD_BALANCE domain"
" has parent");
break;
}
printk("span %s\n", str);
if (!cpu_isset(cpu, sd->span))
printk(KERN_ERR "ERROR: domain->span does not contain "
"CPU%d\n", cpu);
if (!cpu_isset(cpu, group->cpumask))
printk(KERN_ERR "ERROR: domain->groups does not contain"
" CPU%d\n", cpu);
printk(KERN_DEBUG);
for (i = 0; i < level + 2; i++)
printk(" ");
printk("groups:");
do {
if (!group) {
printk("\n");
printk(KERN_ERR "ERROR: group is NULL\n");
break;
}
if (!group->__cpu_power) {
printk("\n");
printk(KERN_ERR "ERROR: domain->cpu_power not "
"set\n");
}
if (!cpus_weight(group->cpumask)) {
printk("\n");
printk(KERN_ERR "ERROR: empty group\n");
}
if (cpus_intersects(groupmask, group->cpumask)) {
printk("\n");
printk(KERN_ERR "ERROR: repeated CPUs\n");
}
cpus_or(groupmask, groupmask, group->cpumask);
cpumask_scnprintf(str, NR_CPUS, group->cpumask);
printk(" %s", str);
group = group->next;
} while (group != sd->groups);
printk("\n");
if (!cpus_equal(sd->span, groupmask))
printk(KERN_ERR "ERROR: groups don't span "
"domain->span\n");
level++;
sd = sd->parent;
if (!sd)
continue;
if (!cpus_subset(groupmask, sd->span))
printk(KERN_ERR "ERROR: parent span is not a superset "
"of domain->span\n");
} while (sd);
}
#else
# define sched_domain_debug(sd, cpu) do { } while (0)
#endif
static int sd_degenerate(struct sched_domain *sd)
{
if (cpus_weight(sd->span) == 1)
return 1;
/* Following flags need at least 2 groups */
if (sd->flags & (SD_LOAD_BALANCE |
SD_BALANCE_NEWIDLE |
SD_BALANCE_FORK |
SD_BALANCE_EXEC |
SD_SHARE_CPUPOWER |
SD_SHARE_PKG_RESOURCES)) {
if (sd->groups != sd->groups->next)
return 0;
}
/* Following flags don't use groups */
if (sd->flags & (SD_WAKE_IDLE |
SD_WAKE_AFFINE |
SD_WAKE_BALANCE))
return 0;
return 1;
}
static int
sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
{
unsigned long cflags = sd->flags, pflags = parent->flags;
if (sd_degenerate(parent))
return 1;
if (!cpus_equal(sd->span, parent->span))
return 0;
/* Does parent contain flags not in child? */
/* WAKE_BALANCE is a subset of WAKE_AFFINE */
if (cflags & SD_WAKE_AFFINE)
pflags &= ~SD_WAKE_BALANCE;
/* Flags needing groups don't count if only 1 group in parent */
if (parent->groups == parent->groups->next) {
pflags &= ~(SD_LOAD_BALANCE |
SD_BALANCE_NEWIDLE |
SD_BALANCE_FORK |
SD_BALANCE_EXEC |
SD_SHARE_CPUPOWER |
SD_SHARE_PKG_RESOURCES);
}
if (~cflags & pflags)
return 0;
return 1;
}
/*
* Attach the domain 'sd' to 'cpu' as its base domain. Callers must
* hold the hotplug lock.
*/
static void cpu_attach_domain(struct sched_domain *sd, int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; tmp = tmp->parent) {
struct sched_domain *parent = tmp->parent;
if (!parent)
break;
if (sd_parent_degenerate(tmp, parent)) {
tmp->parent = parent->parent;
if (parent->parent)
parent->parent->child = tmp;
}
}
if (sd && sd_degenerate(sd)) {
sd = sd->parent;
if (sd)
sd->child = NULL;
}
sched_domain_debug(sd, cpu);
rcu_assign_pointer(rq->sd, sd);
}
/* cpus with isolated domains */
static cpumask_t cpu_isolated_map = CPU_MASK_NONE;
/* Setup the mask of cpus configured for isolated domains */
static int __init isolated_cpu_setup(char *str)
{
int ints[NR_CPUS], i;
str = get_options(str, ARRAY_SIZE(ints), ints);
cpus_clear(cpu_isolated_map);
for (i = 1; i <= ints[0]; i++)
if (ints[i] < NR_CPUS)
cpu_set(ints[i], cpu_isolated_map);
return 1;
}
__setup ("isolcpus=", isolated_cpu_setup);
/*
* init_sched_build_groups takes the cpumask we wish to span, and a pointer
* to a function which identifies what group(along with sched group) a CPU
* belongs to. The return value of group_fn must be a >= 0 and < NR_CPUS
* (due to the fact that we keep track of groups covered with a cpumask_t).
*
* init_sched_build_groups will build a circular linked list of the groups
* covered by the given span, and will set each group's ->cpumask correctly,
* and ->cpu_power to 0.
*/
static void
init_sched_build_groups(cpumask_t span, const cpumask_t *cpu_map,
int (*group_fn)(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg))
{
struct sched_group *first = NULL, *last = NULL;
cpumask_t covered = CPU_MASK_NONE;
int i;
for_each_cpu_mask(i, span) {
struct sched_group *sg;
int group = group_fn(i, cpu_map, &sg);
int j;
if (cpu_isset(i, covered))
continue;
sg->cpumask = CPU_MASK_NONE;
sg->__cpu_power = 0;
for_each_cpu_mask(j, span) {
if (group_fn(j, cpu_map, NULL) != group)
continue;
cpu_set(j, covered);
cpu_set(j, sg->cpumask);
}
if (!first)
first = sg;
if (last)
last->next = sg;
last = sg;
}
last->next = first;
}
#define SD_NODES_PER_DOMAIN 16
/*
* Self-tuning task migration cost measurement between source and target CPUs.
*
* This is done by measuring the cost of manipulating buffers of varying
* sizes. For a given buffer-size here are the steps that are taken:
*
* 1) the source CPU reads+dirties a shared buffer
* 2) the target CPU reads+dirties the same shared buffer
*
* We measure how long they take, in the following 4 scenarios:
*
* - source: CPU1, target: CPU2 | cost1
* - source: CPU2, target: CPU1 | cost2
* - source: CPU1, target: CPU1 | cost3
* - source: CPU2, target: CPU2 | cost4
*
* We then calculate the cost3+cost4-cost1-cost2 difference - this is
* the cost of migration.
*
* We then start off from a small buffer-size and iterate up to larger
* buffer sizes, in 5% steps - measuring each buffer-size separately, and
* doing a maximum search for the cost. (The maximum cost for a migration
* normally occurs when the working set size is around the effective cache
* size.)
*/
#define SEARCH_SCOPE 2
#define MIN_CACHE_SIZE (64*1024U)
#define DEFAULT_CACHE_SIZE (5*1024*1024U)
#define ITERATIONS 1
#define SIZE_THRESH 130
#define COST_THRESH 130
/*
* The migration cost is a function of 'domain distance'. Domain
* distance is the number of steps a CPU has to iterate down its
* domain tree to share a domain with the other CPU. The farther
* two CPUs are from each other, the larger the distance gets.
*
* Note that we use the distance only to cache measurement results,
* the distance value is not used numerically otherwise. When two
* CPUs have the same distance it is assumed that the migration
* cost is the same. (this is a simplification but quite practical)
*/
#define MAX_DOMAIN_DISTANCE 32
static unsigned long long migration_cost[MAX_DOMAIN_DISTANCE] =
{ [ 0 ... MAX_DOMAIN_DISTANCE-1 ] =
/*
* Architectures may override the migration cost and thus avoid
* boot-time calibration. Unit is nanoseconds. Mostly useful for
* virtualized hardware:
*/
#ifdef CONFIG_DEFAULT_MIGRATION_COST
CONFIG_DEFAULT_MIGRATION_COST
#else
-1LL
#endif
};
/*
* Allow override of migration cost - in units of microseconds.
* E.g. migration_cost=1000,2000,3000 will set up a level-1 cost
* of 1 msec, level-2 cost of 2 msecs and level3 cost of 3 msecs:
*/
static int __init migration_cost_setup(char *str)
{
int ints[MAX_DOMAIN_DISTANCE+1], i;
str = get_options(str, ARRAY_SIZE(ints), ints);
printk("#ints: %d\n", ints[0]);
for (i = 1; i <= ints[0]; i++) {
migration_cost[i-1] = (unsigned long long)ints[i]*1000;
printk("migration_cost[%d]: %Ld\n", i-1, migration_cost[i-1]);
}
return 1;
}
__setup ("migration_cost=", migration_cost_setup);
/*
* Global multiplier (divisor) for migration-cutoff values,
* in percentiles. E.g. use a value of 150 to get 1.5 times
* longer cache-hot cutoff times.
*
* (We scale it from 100 to 128 to long long handling easier.)
*/
#define MIGRATION_FACTOR_SCALE 128
static unsigned int migration_factor = MIGRATION_FACTOR_SCALE;
static int __init setup_migration_factor(char *str)
{
get_option(&str, &migration_factor);
migration_factor = migration_factor * MIGRATION_FACTOR_SCALE / 100;
return 1;
}
__setup("migration_factor=", setup_migration_factor);
/*
* Estimated distance of two CPUs, measured via the number of domains
* we have to pass for the two CPUs to be in the same span:
*/
static unsigned long domain_distance(int cpu1, int cpu2)
{
unsigned long distance = 0;
struct sched_domain *sd;
for_each_domain(cpu1, sd) {
WARN_ON(!cpu_isset(cpu1, sd->span));
if (cpu_isset(cpu2, sd->span))
return distance;
distance++;
}
if (distance >= MAX_DOMAIN_DISTANCE) {
WARN_ON(1);
distance = MAX_DOMAIN_DISTANCE-1;
}
return distance;
}
static unsigned int migration_debug;
static int __init setup_migration_debug(char *str)
{
get_option(&str, &migration_debug);
return 1;
}
__setup("migration_debug=", setup_migration_debug);
/*
* Maximum cache-size that the scheduler should try to measure.
* Architectures with larger caches should tune this up during
* bootup. Gets used in the domain-setup code (i.e. during SMP
* bootup).
*/
unsigned int max_cache_size;
static int __init setup_max_cache_size(char *str)
{
get_option(&str, &max_cache_size);
return 1;
}
__setup("max_cache_size=", setup_max_cache_size);
/*
* Dirty a big buffer in a hard-to-predict (for the L2 cache) way. This
* is the operation that is timed, so we try to generate unpredictable
* cachemisses that still end up filling the L2 cache:
*/
static void touch_cache(void *__cache, unsigned long __size)
{
unsigned long size = __size / sizeof(long);
unsigned long chunk1 = size / 3;
unsigned long chunk2 = 2 * size / 3;
unsigned long *cache = __cache;
int i;
for (i = 0; i < size/6; i += 8) {
switch (i % 6) {
case 0: cache[i]++;
case 1: cache[size-1-i]++;
case 2: cache[chunk1-i]++;
case 3: cache[chunk1+i]++;
case 4: cache[chunk2-i]++;
case 5: cache[chunk2+i]++;
}
}
}
/*
* Measure the cache-cost of one task migration. Returns in units of nsec.
*/
static unsigned long long
measure_one(void *cache, unsigned long size, int source, int target)
{
cpumask_t mask, saved_mask;
unsigned long long t0, t1, t2, t3, cost;
saved_mask = current->cpus_allowed;
/*
* Flush source caches to RAM and invalidate them:
*/
sched_cacheflush();
/*
* Migrate to the source CPU:
*/
mask = cpumask_of_cpu(source);
set_cpus_allowed(current, mask);
WARN_ON(smp_processor_id() != source);
/*
* Dirty the working set:
*/
t0 = sched_clock();
touch_cache(cache, size);
t1 = sched_clock();
/*
* Migrate to the target CPU, dirty the L2 cache and access
* the shared buffer. (which represents the working set
* of a migrated task.)
*/
mask = cpumask_of_cpu(target);
set_cpus_allowed(current, mask);
WARN_ON(smp_processor_id() != target);
t2 = sched_clock();
touch_cache(cache, size);
t3 = sched_clock();
cost = t1-t0 + t3-t2;
if (migration_debug >= 2)
printk("[%d->%d]: %8Ld %8Ld %8Ld => %10Ld.\n",
source, target, t1-t0, t1-t0, t3-t2, cost);
/*
* Flush target caches to RAM and invalidate them:
*/
sched_cacheflush();
set_cpus_allowed(current, saved_mask);
return cost;
}
/*
* Measure a series of task migrations and return the average
* result. Since this code runs early during bootup the system
* is 'undisturbed' and the average latency makes sense.
*
* The algorithm in essence auto-detects the relevant cache-size,
* so it will properly detect different cachesizes for different
* cache-hierarchies, depending on how the CPUs are connected.
*
* Architectures can prime the upper limit of the search range via
* max_cache_size, otherwise the search range defaults to 20MB...64K.
*/
static unsigned long long
measure_cost(int cpu1, int cpu2, void *cache, unsigned int size)
{
unsigned long long cost1, cost2;
int i;
/*
* Measure the migration cost of 'size' bytes, over an
* average of 10 runs:
*
* (We perturb the cache size by a small (0..4k)
* value to compensate size/alignment related artifacts.
* We also subtract the cost of the operation done on
* the same CPU.)
*/
cost1 = 0;
/*
* dry run, to make sure we start off cache-cold on cpu1,
* and to get any vmalloc pagefaults in advance:
*/
measure_one(cache, size, cpu1, cpu2);
for (i = 0; i < ITERATIONS; i++)
cost1 += measure_one(cache, size - i * 1024, cpu1, cpu2);
measure_one(cache, size, cpu2, cpu1);
for (i = 0; i < ITERATIONS; i++)
cost1 += measure_one(cache, size - i * 1024, cpu2, cpu1);
/*
* (We measure the non-migrating [cached] cost on both
* cpu1 and cpu2, to handle CPUs with different speeds)
*/
cost2 = 0;
measure_one(cache, size, cpu1, cpu1);
for (i = 0; i < ITERATIONS; i++)
cost2 += measure_one(cache, size - i * 1024, cpu1, cpu1);
measure_one(cache, size, cpu2, cpu2);
for (i = 0; i < ITERATIONS; i++)
cost2 += measure_one(cache, size - i * 1024, cpu2, cpu2);
/*
* Get the per-iteration migration cost:
*/
do_div(cost1, 2 * ITERATIONS);
do_div(cost2, 2 * ITERATIONS);
return cost1 - cost2;
}
static unsigned long long measure_migration_cost(int cpu1, int cpu2)
{
unsigned long long max_cost = 0, fluct = 0, avg_fluct = 0;
unsigned int max_size, size, size_found = 0;
long long cost = 0, prev_cost;
void *cache;
/*
* Search from max_cache_size*5 down to 64K - the real relevant
* cachesize has to lie somewhere inbetween.
*/
if (max_cache_size) {
max_size = max(max_cache_size * SEARCH_SCOPE, MIN_CACHE_SIZE);
size = max(max_cache_size / SEARCH_SCOPE, MIN_CACHE_SIZE);
} else {
/*
* Since we have no estimation about the relevant
* search range
*/
max_size = DEFAULT_CACHE_SIZE * SEARCH_SCOPE;
size = MIN_CACHE_SIZE;
}
if (!cpu_online(cpu1) || !cpu_online(cpu2)) {
printk("cpu %d and %d not both online!\n", cpu1, cpu2);
return 0;
}
/*
* Allocate the working set:
*/
cache = vmalloc(max_size);
if (!cache) {
printk("could not vmalloc %d bytes for cache!\n", 2 * max_size);
return 1000000; /* return 1 msec on very small boxen */
}
while (size <= max_size) {
prev_cost = cost;
cost = measure_cost(cpu1, cpu2, cache, size);
/*
* Update the max:
*/
if (cost > 0) {
if (max_cost < cost) {
max_cost = cost;
size_found = size;
}
}
/*
* Calculate average fluctuation, we use this to prevent
* noise from triggering an early break out of the loop:
*/
fluct = abs(cost - prev_cost);
avg_fluct = (avg_fluct + fluct)/2;
if (migration_debug)
printk("-> [%d][%d][%7d] %3ld.%ld [%3ld.%ld] (%ld): "
"(%8Ld %8Ld)\n",
cpu1, cpu2, size,
(long)cost / 1000000,
((long)cost / 100000) % 10,
(long)max_cost / 1000000,
((long)max_cost / 100000) % 10,
domain_distance(cpu1, cpu2),
cost, avg_fluct);
/*
* If we iterated at least 20% past the previous maximum,
* and the cost has dropped by more than 20% already,
* (taking fluctuations into account) then we assume to
* have found the maximum and break out of the loop early:
*/
if (size_found && (size*100 > size_found*SIZE_THRESH))
if (cost+avg_fluct <= 0 ||
max_cost*100 > (cost+avg_fluct)*COST_THRESH) {
if (migration_debug)
printk("-> found max.\n");
break;
}
/*
* Increase the cachesize in 10% steps:
*/
size = size * 10 / 9;
}
if (migration_debug)
printk("[%d][%d] working set size found: %d, cost: %Ld\n",
cpu1, cpu2, size_found, max_cost);
vfree(cache);
/*
* A task is considered 'cache cold' if at least 2 times
* the worst-case cost of migration has passed.
*
* (this limit is only listened to if the load-balancing
* situation is 'nice' - if there is a large imbalance we
* ignore it for the sake of CPU utilization and
* processing fairness.)
*/
return 2 * max_cost * migration_factor / MIGRATION_FACTOR_SCALE;
}
static void calibrate_migration_costs(const cpumask_t *cpu_map)
{
int cpu1 = -1, cpu2 = -1, cpu, orig_cpu = raw_smp_processor_id();
unsigned long j0, j1, distance, max_distance = 0;
struct sched_domain *sd;
j0 = jiffies;
/*
* First pass - calculate the cacheflush times:
*/
for_each_cpu_mask(cpu1, *cpu_map) {
for_each_cpu_mask(cpu2, *cpu_map) {
if (cpu1 == cpu2)
continue;
distance = domain_distance(cpu1, cpu2);
max_distance = max(max_distance, distance);
/*
* No result cached yet?
*/
if (migration_cost[distance] == -1LL)
migration_cost[distance] =
measure_migration_cost(cpu1, cpu2);
}
}
/*
* Second pass - update the sched domain hierarchy with
* the new cache-hot-time estimations:
*/
for_each_cpu_mask(cpu, *cpu_map) {
distance = 0;
for_each_domain(cpu, sd) {
sd->cache_hot_time = migration_cost[distance];
distance++;
}
}
/*
* Print the matrix:
*/
if (migration_debug)
printk("migration: max_cache_size: %d, cpu: %d MHz:\n",
max_cache_size,
#ifdef CONFIG_X86
cpu_khz/1000
#else
-1
#endif
);
if (system_state == SYSTEM_BOOTING && num_online_cpus() > 1) {
printk("migration_cost=");
for (distance = 0; distance <= max_distance; distance++) {
if (distance)
printk(",");
printk("%ld", (long)migration_cost[distance] / 1000);
}
printk("\n");
}
j1 = jiffies;
if (migration_debug)
printk("migration: %ld seconds\n", (j1-j0) / HZ);
/*
* Move back to the original CPU. NUMA-Q gets confused
* if we migrate to another quad during bootup.
*/
if (raw_smp_processor_id() != orig_cpu) {
cpumask_t mask = cpumask_of_cpu(orig_cpu),
saved_mask = current->cpus_allowed;
set_cpus_allowed(current, mask);
set_cpus_allowed(current, saved_mask);
}
}
#ifdef CONFIG_NUMA
/**
* find_next_best_node - find the next node to include in a sched_domain
* @node: node whose sched_domain we're building
* @used_nodes: nodes already in the sched_domain
*
* Find the next node to include in a given scheduling domain. Simply
* finds the closest node not already in the @used_nodes map.
*
* Should use nodemask_t.
*/
static int find_next_best_node(int node, unsigned long *used_nodes)
{
int i, n, val, min_val, best_node = 0;
min_val = INT_MAX;
for (i = 0; i < MAX_NUMNODES; i++) {
/* Start at @node */
n = (node + i) % MAX_NUMNODES;
if (!nr_cpus_node(n))
continue;
/* Skip already used nodes */
if (test_bit(n, used_nodes))
continue;
/* Simple min distance search */
val = node_distance(node, n);
if (val < min_val) {
min_val = val;
best_node = n;
}
}
set_bit(best_node, used_nodes);
return best_node;
}
/**
* sched_domain_node_span - get a cpumask for a node's sched_domain
* @node: node whose cpumask we're constructing
* @size: number of nodes to include in this span
*
* Given a node, construct a good cpumask for its sched_domain to span. It
* should be one that prevents unnecessary balancing, but also spreads tasks
* out optimally.
*/
static cpumask_t sched_domain_node_span(int node)
{
DECLARE_BITMAP(used_nodes, MAX_NUMNODES);
cpumask_t span, nodemask;
int i;
cpus_clear(span);
bitmap_zero(used_nodes, MAX_NUMNODES);
nodemask = node_to_cpumask(node);
cpus_or(span, span, nodemask);
set_bit(node, used_nodes);
for (i = 1; i < SD_NODES_PER_DOMAIN; i++) {
int next_node = find_next_best_node(node, used_nodes);
nodemask = node_to_cpumask(next_node);
cpus_or(span, span, nodemask);
}
return span;
}
#endif
int sched_smt_power_savings = 0, sched_mc_power_savings = 0;
/*
* SMT sched-domains:
*/
#ifdef CONFIG_SCHED_SMT
static DEFINE_PER_CPU(struct sched_domain, cpu_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_cpus);
static int cpu_to_cpu_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg)
{
if (sg)
*sg = &per_cpu(sched_group_cpus, cpu);
return cpu;
}
#endif
/*
* multi-core sched-domains:
*/
#ifdef CONFIG_SCHED_MC
static DEFINE_PER_CPU(struct sched_domain, core_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_core);
#endif
#if defined(CONFIG_SCHED_MC) && defined(CONFIG_SCHED_SMT)
static int cpu_to_core_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg)
{
int group;
cpumask_t mask = cpu_sibling_map[cpu];
cpus_and(mask, mask, *cpu_map);
group = first_cpu(mask);
if (sg)
*sg = &per_cpu(sched_group_core, group);
return group;
}
#elif defined(CONFIG_SCHED_MC)
static int cpu_to_core_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg)
{
if (sg)
*sg = &per_cpu(sched_group_core, cpu);
return cpu;
}
#endif
static DEFINE_PER_CPU(struct sched_domain, phys_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_phys);
static int cpu_to_phys_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg)
{
int group;
#ifdef CONFIG_SCHED_MC
cpumask_t mask = cpu_coregroup_map(cpu);
cpus_and(mask, mask, *cpu_map);
group = first_cpu(mask);
#elif defined(CONFIG_SCHED_SMT)
cpumask_t mask = cpu_sibling_map[cpu];
cpus_and(mask, mask, *cpu_map);
group = first_cpu(mask);
#else
group = cpu;
#endif
if (sg)
*sg = &per_cpu(sched_group_phys, group);
return group;
}
#ifdef CONFIG_NUMA
/*
* The init_sched_build_groups can't handle what we want to do with node
* groups, so roll our own. Now each node has its own list of groups which
* gets dynamically allocated.
*/
static DEFINE_PER_CPU(struct sched_domain, node_domains);
static struct sched_group **sched_group_nodes_bycpu[NR_CPUS];
static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
static DEFINE_PER_CPU(struct sched_group, sched_group_allnodes);
static int cpu_to_allnodes_group(int cpu, const cpumask_t *cpu_map,
struct sched_group **sg)
{
cpumask_t nodemask = node_to_cpumask(cpu_to_node(cpu));
int group;
cpus_and(nodemask, nodemask, *cpu_map);
group = first_cpu(nodemask);
if (sg)
*sg = &per_cpu(sched_group_allnodes, group);
return group;
}
static void init_numa_sched_groups_power(struct sched_group *group_head)
{
struct sched_group *sg = group_head;
int j;
if (!sg)
return;
next_sg:
for_each_cpu_mask(j, sg->cpumask) {
struct sched_domain *sd;
sd = &per_cpu(phys_domains, j);
if (j != first_cpu(sd->groups->cpumask)) {
/*
* Only add "power" once for each
* physical package.
*/
continue;
}
sg_inc_cpu_power(sg, sd->groups->__cpu_power);
}
sg = sg->next;
if (sg != group_head)
goto next_sg;
}
#endif
#ifdef CONFIG_NUMA
/* Free memory allocated for various sched_group structures */
static void free_sched_groups(const cpumask_t *cpu_map)
{
int cpu, i;
for_each_cpu_mask(cpu, *cpu_map) {
struct sched_group **sched_group_nodes
= sched_group_nodes_bycpu[cpu];
if (!sched_group_nodes)
continue;
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);
struct sched_group *oldsg, *sg = sched_group_nodes[i];
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask))
continue;
if (sg == NULL)
continue;
sg = sg->next;
next_sg:
oldsg = sg;
sg = sg->next;
kfree(oldsg);
if (oldsg != sched_group_nodes[i])
goto next_sg;
}
kfree(sched_group_nodes);
sched_group_nodes_bycpu[cpu] = NULL;
}
}
#else
static void free_sched_groups(const cpumask_t *cpu_map)
{
}
#endif
/*
* Initialize sched groups cpu_power.
*
* cpu_power indicates the capacity of sched group, which is used while
* distributing the load between different sched groups in a sched domain.
* Typically cpu_power for all the groups in a sched domain will be same unless
* there are asymmetries in the topology. If there are asymmetries, group
* having more cpu_power will pickup more load compared to the group having
* less cpu_power.
*
* cpu_power will be a multiple of SCHED_LOAD_SCALE. This multiple represents
* the maximum number of tasks a group can handle in the presence of other idle
* or lightly loaded groups in the same sched domain.
*/
static void init_sched_groups_power(int cpu, struct sched_domain *sd)
{
struct sched_domain *child;
struct sched_group *group;
WARN_ON(!sd || !sd->groups);
if (cpu != first_cpu(sd->groups->cpumask))
return;
child = sd->child;
sd->groups->__cpu_power = 0;
/*
* For perf policy, if the groups in child domain share resources
* (for example cores sharing some portions of the cache hierarchy
* or SMT), then set this domain groups cpu_power such that each group
* can handle only one task, when there are other idle groups in the
* same sched domain.
*/
if (!child || (!(sd->flags & SD_POWERSAVINGS_BALANCE) &&
(child->flags &
(SD_SHARE_CPUPOWER | SD_SHARE_PKG_RESOURCES)))) {
sg_inc_cpu_power(sd->groups, SCHED_LOAD_SCALE);
return;
}
/*
* add cpu_power of each child group to this groups cpu_power
*/
group = child->groups;
do {
sg_inc_cpu_power(sd->groups, group->__cpu_power);
group = group->next;
} while (group != child->groups);
}
/*
* Build sched domains for a given set of cpus and attach the sched domains
* to the individual cpus
*/
static int build_sched_domains(const cpumask_t *cpu_map)
{
int i;
struct sched_domain *sd;
#ifdef CONFIG_NUMA
struct sched_group **sched_group_nodes = NULL;
int sd_allnodes = 0;
/*
* Allocate the per-node list of sched groups
*/
sched_group_nodes = kzalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
GFP_KERNEL);
if (!sched_group_nodes) {
printk(KERN_WARNING "Can not alloc sched group node list\n");
return -ENOMEM;
}
sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
#endif
/*
* Set up domains for cpus specified by the cpu_map.
*/
for_each_cpu_mask(i, *cpu_map) {
struct sched_domain *sd = NULL, *p;
cpumask_t nodemask = node_to_cpumask(cpu_to_node(i));
cpus_and(nodemask, nodemask, *cpu_map);
#ifdef CONFIG_NUMA
if (cpus_weight(*cpu_map)
> SD_NODES_PER_DOMAIN*cpus_weight(nodemask)) {
sd = &per_cpu(allnodes_domains, i);
*sd = SD_ALLNODES_INIT;
sd->span = *cpu_map;
cpu_to_allnodes_group(i, cpu_map, &sd->groups);
p = sd;
sd_allnodes = 1;
} else
p = NULL;
sd = &per_cpu(node_domains, i);
*sd = SD_NODE_INIT;
sd->span = sched_domain_node_span(cpu_to_node(i));
sd->parent = p;
if (p)
p->child = sd;
cpus_and(sd->span, sd->span, *cpu_map);
#endif
p = sd;
sd = &per_cpu(phys_domains, i);
*sd = SD_CPU_INIT;
sd->span = nodemask;
sd->parent = p;
if (p)
p->child = sd;
cpu_to_phys_group(i, cpu_map, &sd->groups);
#ifdef CONFIG_SCHED_MC
p = sd;
sd = &per_cpu(core_domains, i);
*sd = SD_MC_INIT;
sd->span = cpu_coregroup_map(i);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
cpu_to_core_group(i, cpu_map, &sd->groups);
#endif
#ifdef CONFIG_SCHED_SMT
p = sd;
sd = &per_cpu(cpu_domains, i);
*sd = SD_SIBLING_INIT;
sd->span = cpu_sibling_map[i];
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
cpu_to_cpu_group(i, cpu_map, &sd->groups);
#endif
}
#ifdef CONFIG_SCHED_SMT
/* Set up CPU (sibling) groups */
for_each_cpu_mask(i, *cpu_map) {
cpumask_t this_sibling_map = cpu_sibling_map[i];
cpus_and(this_sibling_map, this_sibling_map, *cpu_map);
if (i != first_cpu(this_sibling_map))
continue;
init_sched_build_groups(this_sibling_map, cpu_map, &cpu_to_cpu_group);
}
#endif
#ifdef CONFIG_SCHED_MC
/* Set up multi-core groups */
for_each_cpu_mask(i, *cpu_map) {
cpumask_t this_core_map = cpu_coregroup_map(i);
cpus_and(this_core_map, this_core_map, *cpu_map);
if (i != first_cpu(this_core_map))
continue;
init_sched_build_groups(this_core_map, cpu_map, &cpu_to_core_group);
}
#endif
/* Set up physical groups */
for (i = 0; i < MAX_NUMNODES; i++) {
cpumask_t nodemask = node_to_cpumask(i);
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask))
continue;
init_sched_build_groups(nodemask, cpu_map, &cpu_to_phys_group);
}
#ifdef CONFIG_NUMA
/* Set up node groups */
if (sd_allnodes)
init_sched_build_groups(*cpu_map, cpu_map, &cpu_to_allnodes_group);
for (i = 0; i < MAX_NUMNODES; i++) {
/* Set up node groups */
struct sched_group *sg, *prev;
cpumask_t nodemask = node_to_cpumask(i);
cpumask_t domainspan;
cpumask_t covered = CPU_MASK_NONE;
int j;
cpus_and(nodemask, nodemask, *cpu_map);
if (cpus_empty(nodemask)) {
sched_group_nodes[i] = NULL;
continue;
}
domainspan = sched_domain_node_span(i);
cpus_and(domainspan, domainspan, *cpu_map);
sg = kmalloc_node(sizeof(struct sched_group), GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING "Can not alloc domain group for "
"node %d\n", i);
goto error;
}
sched_group_nodes[i] = sg;
for_each_cpu_mask(j, nodemask) {
struct sched_domain *sd;
sd = &per_cpu(node_domains, j);
sd->groups = sg;
}
sg->__cpu_power = 0;
sg->cpumask = nodemask;
sg->next = sg;
cpus_or(covered, covered, nodemask);
prev = sg;
for (j = 0; j < MAX_NUMNODES; j++) {
cpumask_t tmp, notcovered;
int n = (i + j) % MAX_NUMNODES;
cpus_complement(notcovered, covered);
cpus_and(tmp, notcovered, *cpu_map);
cpus_and(tmp, tmp, domainspan);
if (cpus_empty(tmp))
break;
nodemask = node_to_cpumask(n);
cpus_and(tmp, tmp, nodemask);
if (cpus_empty(tmp))
continue;
sg = kmalloc_node(sizeof(struct sched_group),
GFP_KERNEL, i);
if (!sg) {
printk(KERN_WARNING
"Can not alloc domain group for node %d\n", j);
goto error;
}
sg->__cpu_power = 0;
sg->cpumask = tmp;
sg->next = prev->next;
cpus_or(covered, covered, tmp);
prev->next = sg;
prev = sg;
}
}
#endif
/* Calculate CPU power for physical packages and nodes */
#ifdef CONFIG_SCHED_SMT
for_each_cpu_mask(i, *cpu_map) {
sd = &per_cpu(cpu_domains, i);
init_sched_groups_power(i, sd);
}
#endif
#ifdef CONFIG_SCHED_MC
for_each_cpu_mask(i, *cpu_map) {
sd = &per_cpu(core_domains, i);
init_sched_groups_power(i, sd);
}
#endif
for_each_cpu_mask(i, *cpu_map) {
sd = &per_cpu(phys_domains, i);
init_sched_groups_power(i, sd);
}
#ifdef CONFIG_NUMA
for (i = 0; i < MAX_NUMNODES; i++)
init_numa_sched_groups_power(sched_group_nodes[i]);
if (sd_allnodes) {
struct sched_group *sg;
cpu_to_allnodes_group(first_cpu(*cpu_map), cpu_map, &sg);
init_numa_sched_groups_power(sg);
}
#endif
/* Attach the domains */
for_each_cpu_mask(i, *cpu_map) {
struct sched_domain *sd;
#ifdef CONFIG_SCHED_SMT
sd = &per_cpu(cpu_domains, i);
#elif defined(CONFIG_SCHED_MC)
sd = &per_cpu(core_domains, i);
#else
sd = &per_cpu(phys_domains, i);
#endif
cpu_attach_domain(sd, i);
}
/*
* Tune cache-hot values:
*/
calibrate_migration_costs(cpu_map);
return 0;
#ifdef CONFIG_NUMA
error:
free_sched_groups(cpu_map);
return -ENOMEM;
#endif
}
/*
* Set up scheduler domains and groups. Callers must hold the hotplug lock.
*/
static int arch_init_sched_domains(const cpumask_t *cpu_map)
{
cpumask_t cpu_default_map;
int err;
/*
* Setup mask for cpus without special case scheduling requirements.
* For now this just excludes isolated cpus, but could be used to
* exclude other special cases in the future.
*/
cpus_andnot(cpu_default_map, *cpu_map, cpu_isolated_map);
err = build_sched_domains(&cpu_default_map);
return err;
}
static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
{
free_sched_groups(cpu_map);
}
/*
* Detach sched domains from a group of cpus specified in cpu_map
* These cpus will now be attached to the NULL domain
*/
static void detach_destroy_domains(const cpumask_t *cpu_map)
{
int i;
for_each_cpu_mask(i, *cpu_map)
cpu_attach_domain(NULL, i);
synchronize_sched();
arch_destroy_sched_domains(cpu_map);
}
/*
* Partition sched domains as specified by the cpumasks below.
* This attaches all cpus from the cpumasks to the NULL domain,
* waits for a RCU quiescent period, recalculates sched
* domain information and then attaches them back to the
* correct sched domains
* Call with hotplug lock held
*/
int partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
{
cpumask_t change_map;
int err = 0;
cpus_and(*partition1, *partition1, cpu_online_map);
cpus_and(*partition2, *partition2, cpu_online_map);
cpus_or(change_map, *partition1, *partition2);
/* Detach sched domains from all of the affected cpus */
detach_destroy_domains(&change_map);
if (!cpus_empty(*partition1))
err = build_sched_domains(partition1);
if (!err && !cpus_empty(*partition2))
err = build_sched_domains(partition2);
return err;
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
int arch_reinit_sched_domains(void)
{
int err;
mutex_lock(&sched_hotcpu_mutex);
detach_destroy_domains(&cpu_online_map);
err = arch_init_sched_domains(&cpu_online_map);
mutex_unlock(&sched_hotcpu_mutex);
return err;
}
static ssize_t sched_power_savings_store(const char *buf, size_t count, int smt)
{
int ret;
if (buf[0] != '0' && buf[0] != '1')
return -EINVAL;
if (smt)
sched_smt_power_savings = (buf[0] == '1');
else
sched_mc_power_savings = (buf[0] == '1');
ret = arch_reinit_sched_domains();
return ret ? ret : count;
}
int sched_create_sysfs_power_savings_entries(struct sysdev_class *cls)
{
int err = 0;
#ifdef CONFIG_SCHED_SMT
if (smt_capable())
err = sysfs_create_file(&cls->kset.kobj,
&attr_sched_smt_power_savings.attr);
#endif
#ifdef CONFIG_SCHED_MC
if (!err && mc_capable())
err = sysfs_create_file(&cls->kset.kobj,
&attr_sched_mc_power_savings.attr);
#endif
return err;
}
#endif
#ifdef CONFIG_SCHED_MC
static ssize_t sched_mc_power_savings_show(struct sys_device *dev, char *page)
{
return sprintf(page, "%u\n", sched_mc_power_savings);
}
static ssize_t sched_mc_power_savings_store(struct sys_device *dev,
const char *buf, size_t count)
{
return sched_power_savings_store(buf, count, 0);
}
SYSDEV_ATTR(sched_mc_power_savings, 0644, sched_mc_power_savings_show,
sched_mc_power_savings_store);
#endif
#ifdef CONFIG_SCHED_SMT
static ssize_t sched_smt_power_savings_show(struct sys_device *dev, char *page)
{
return sprintf(page, "%u\n", sched_smt_power_savings);
}
static ssize_t sched_smt_power_savings_store(struct sys_device *dev,
const char *buf, size_t count)
{
return sched_power_savings_store(buf, count, 1);
}
SYSDEV_ATTR(sched_smt_power_savings, 0644, sched_smt_power_savings_show,
sched_smt_power_savings_store);
#endif
/*
* Force a reinitialization of the sched domains hierarchy. The domains
* and groups cannot be updated in place without racing with the balancing
* code, so we temporarily attach all running cpus to the NULL domain
* which will prevent rebalancing while the sched domains are recalculated.
*/
static int update_sched_domains(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
detach_destroy_domains(&cpu_online_map);
return NOTIFY_OK;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DOWN_FAILED:
case CPU_DOWN_FAILED_FROZEN:
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
/*
* Fall through and re-initialise the domains.
*/
break;
default:
return NOTIFY_DONE;
}
/* The hotplug lock is already held by cpu_up/cpu_down */
arch_init_sched_domains(&cpu_online_map);
return NOTIFY_OK;
}
void __init sched_init_smp(void)
{
cpumask_t non_isolated_cpus;
mutex_lock(&sched_hotcpu_mutex);
arch_init_sched_domains(&cpu_online_map);
cpus_andnot(non_isolated_cpus, cpu_possible_map, cpu_isolated_map);
if (cpus_empty(non_isolated_cpus))
cpu_set(smp_processor_id(), non_isolated_cpus);
mutex_unlock(&sched_hotcpu_mutex);
/* XXX: Theoretical race here - CPU may be hotplugged now */
hotcpu_notifier(update_sched_domains, 0);
/* Move init over to a non-isolated CPU */
if (set_cpus_allowed(current, non_isolated_cpus) < 0)
BUG();
}
#else
void __init sched_init_smp(void)
{
}
#endif /* CONFIG_SMP */
int in_sched_functions(unsigned long addr)
{
/* Linker adds these: start and end of __sched functions */
extern char __sched_text_start[], __sched_text_end[];
return in_lock_functions(addr) ||
(addr >= (unsigned long)__sched_text_start
&& addr < (unsigned long)__sched_text_end);
}
void __init sched_init(void)
{
int i, j, k;
int highest_cpu = 0;
for_each_possible_cpu(i) {
struct prio_array *array;
struct rq *rq;
rq = cpu_rq(i);
spin_lock_init(&rq->lock);
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
rq->best_expired_prio = MAX_PRIO;
#ifdef CONFIG_SMP
rq->sd = NULL;
for (j = 1; j < 3; j++)
rq->cpu_load[j] = 0;
rq->active_balance = 0;
rq->push_cpu = 0;
rq->cpu = i;
rq->migration_thread = NULL;
INIT_LIST_HEAD(&rq->migration_queue);
#endif
atomic_set(&rq->nr_iowait, 0);
for (j = 0; j < 2; j++) {
array = rq->arrays + j;
for (k = 0; k < MAX_PRIO; k++) {
INIT_LIST_HEAD(array->queue + k);
__clear_bit(k, array->bitmap);
}
// delimiter for bitsearch
__set_bit(MAX_PRIO, array->bitmap);
}
highest_cpu = i;
}
set_load_weight(&init_task);
#ifdef CONFIG_SMP
nr_cpu_ids = highest_cpu + 1;
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);
#endif
#ifdef CONFIG_RT_MUTEXES
plist_head_init(&init_task.pi_waiters, &init_task.pi_lock);
#endif
/*
* The boot idle thread does lazy MMU switching as well:
*/
atomic_inc(&init_mm.mm_count);
enter_lazy_tlb(&init_mm, current);
/*
* Make us the idle thread. Technically, schedule() should not be
* called from this thread, however somewhere below it might be,
* but because we are the idle thread, we just pick up running again
* when this runqueue becomes "idle".
*/
init_idle(current, smp_processor_id());
}
#ifdef CONFIG_DEBUG_SPINLOCK_SLEEP
void __might_sleep(char *file, int line)
{
#ifdef in_atomic
static unsigned long prev_jiffy; /* ratelimiting */
if ((in_atomic() || irqs_disabled()) &&
system_state == SYSTEM_RUNNING && !oops_in_progress) {
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
printk(KERN_ERR "BUG: sleeping function called from invalid"
" context at %s:%d\n", file, line);
printk("in_atomic():%d, irqs_disabled():%d\n",
in_atomic(), irqs_disabled());
debug_show_held_locks(current);
if (irqs_disabled())
print_irqtrace_events(current);
dump_stack();
}
#endif
}
EXPORT_SYMBOL(__might_sleep);
#endif
#ifdef CONFIG_MAGIC_SYSRQ
void normalize_rt_tasks(void)
{
struct prio_array *array;
struct task_struct *g, *p;
unsigned long flags;
struct rq *rq;
read_lock_irq(&tasklist_lock);
do_each_thread(g, p) {
if (!rt_task(p))
continue;
spin_lock_irqsave(&p->pi_lock, flags);
rq = __task_rq_lock(p);
array = p->array;
if (array)
deactivate_task(p, task_rq(p));
__setscheduler(p, SCHED_NORMAL, 0);
if (array) {
__activate_task(p, task_rq(p));
resched_task(rq->curr);
}
__task_rq_unlock(rq);
spin_unlock_irqrestore(&p->pi_lock, flags);
} while_each_thread(g, p);
read_unlock_irq(&tasklist_lock);
}
#endif /* CONFIG_MAGIC_SYSRQ */
#ifdef CONFIG_IA64
/*
* These functions are only useful for the IA64 MCA handling.
*
* They can only be called when the whole system has been
* stopped - every CPU needs to be quiescent, and no scheduling
* activity can take place. Using them for anything else would
* be a serious bug, and as a result, they aren't even visible
* under any other configuration.
*/
/**
* curr_task - return the current task for a given cpu.
* @cpu: the processor in question.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*/
struct task_struct *curr_task(int cpu)
{
return cpu_curr(cpu);
}
/**
* set_curr_task - set the current task for a given cpu.
* @cpu: the processor in question.
* @p: the task pointer to set.
*
* Description: This function must only be used when non-maskable interrupts
* are serviced on a separate stack. It allows the architecture to switch the
* notion of the current task on a cpu in a non-blocking manner. This function
* must be called with all CPU's synchronized, and interrupts disabled, the
* and caller must save the original value of the current task (see
* curr_task() above) and restore that value before reenabling interrupts and
* re-starting the system.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*/
void set_curr_task(int cpu, struct task_struct *p)
{
cpu_curr(cpu) = p;
}
#endif
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