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Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Browse Source 
Pull RCU updates from Paul E. McKenney:

  - Documentation updates.

  - Changes permitting use of call_rcu() and friends very early in
    boot, for example, before rcu_init() is invoked.

  - Miscellaneous fixes.

  - Add in-kernel API to enable and disable expediting of normal RCU
    grace periods.

  - Improve RCU's handling of (hotplug-) outgoing CPUs.

    Note: ARM support is lagging a bit here, and these improved
    diagnostics might generate (harmless) splats.

  - NO_HZ_FULL_SYSIDLE fixes.

  - Tiny RCU updates to make it more tiny.

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2015-03-27 10:04:06 +01:00
commit 4bfe186dbe
30 changed files with 948 additions and 437 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

45
Documentation/atomic_ops.txt
View File

@ -201,11 +201,11 @@ These routines add 1 and subtract 1, respectively, from the given
atomic_t and return the new counter value after the operation is
performed.
Unlike the above routines, it is required that explicit memory
barriers are performed before and after the operation. It must be
done such that all memory operations before and after the atomic
operation calls are strongly ordered with respect to the atomic
operation itself.
Unlike the above routines, it is required that these primitives
include explicit memory barriers that are performed before and after
the operation. It must be done such that all memory operations before
and after the atomic operation calls are strongly ordered with respect
to the atomic operation itself.
For example, it should behave as if a smp_mb() call existed both
before and after the atomic operation.
@ -233,21 +233,21 @@ These two routines increment and decrement by 1, respectively, the
given atomic counter. They return a boolean indicating whether the
resulting counter value was zero or not.
It requires explicit memory barrier semantics around the operation as
above.
Again, these primitives provide explicit memory barrier semantics around
the atomic operation.
int atomic_sub_and_test(int i, atomic_t *v);
This is identical to atomic_dec_and_test() except that an explicit
decrement is given instead of the implicit "1". It requires explicit
memory barrier semantics around the operation.
decrement is given instead of the implicit "1". This primitive must
provide explicit memory barrier semantics around the operation.
int atomic_add_negative(int i, atomic_t *v);
The given increment is added to the given atomic counter value. A
boolean is return which indicates whether the resulting counter value
is negative. It requires explicit memory barrier semantics around the
operation.
The given increment is added to the given atomic counter value. A boolean
is return which indicates whether the resulting counter value is negative.
This primitive must provide explicit memory barrier semantics around
the operation.
Then:
@ -257,7 +257,7 @@ This performs an atomic exchange operation on the atomic variable v, setting
the given new value. It returns the old value that the atomic variable v had
just before the operation.
atomic_xchg requires explicit memory barriers around the operation.
atomic_xchg must provide explicit memory barriers around the operation.
int atomic_cmpxchg(atomic_t *v, int old, int new);
@ -266,7 +266,7 @@ with the given old and new values. Like all atomic_xxx operations,
atomic_cmpxchg will only satisfy its atomicity semantics as long as all
other accesses of *v are performed through atomic_xxx operations.
atomic_cmpxchg requires explicit memory barriers around the operation.
atomic_cmpxchg must provide explicit memory barriers around the operation.
The semantics for atomic_cmpxchg are the same as those defined for 'cas'
below.
@ -279,8 +279,8 @@ If the atomic value v is not equal to u, this function adds a to v, and
returns non zero. If v is equal to u then it returns zero. This is done as
an atomic operation.
atomic_add_unless requires explicit memory barriers around the operation
unless it fails (returns 0).
atomic_add_unless must provide explicit memory barriers around the
operation unless it fails (returns 0).
atomic_inc_not_zero, equivalent to atomic_add_unless(v, 1, 0)
@ -460,9 +460,9 @@ the return value into an int. There are other places where things
like this occur as well.
These routines, like the atomic_t counter operations returning values,
require explicit memory barrier semantics around their execution. All
memory operations before the atomic bit operation call must be made
visible globally before the atomic bit operation is made visible.
must provide explicit memory barrier semantics around their execution.
All memory operations before the atomic bit operation call must be
made visible globally before the atomic bit operation is made visible.
Likewise, the atomic bit operation must be visible globally before any
subsequent memory operation is made visible. For example:
@ -536,8 +536,9 @@ except that two underscores are prefixed to the interface name.
These non-atomic variants also do not require any special memory
barrier semantics.
The routines xchg() and cmpxchg() need the same exact memory barriers
as the atomic and bit operations returning values.
The routines xchg() and cmpxchg() must provide the same exact
memory-barrier semantics as the atomic and bit operations returning
values.
Spinlocks and rwlocks have memory barrier expectations as well.
The rule to follow is simple:

20
Documentation/kernel-parameters.txt
View File

@ -2968,6 +2968,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Set maximum number of finished RCU callbacks to
process in one batch.
rcutree.gp_init_delay= [KNL]
Set the number of jiffies to delay each step of
RCU grace-period initialization. This only has
effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
set.
rcutree.rcu_fanout_leaf= [KNL]
Increase the number of CPUs assigned to each
leaf rcu_node structure. Useful for very large
@ -2991,11 +2997,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
value is one, and maximum value is HZ.
rcutree.kthread_prio= [KNL,BOOT]
Set the SCHED_FIFO priority of the RCU
per-CPU kthreads (rcuc/N). This value is also
used for the priority of the RCU boost threads
(rcub/N). Valid values are 1-99 and the default
is 1 (the least-favored priority).
Set the SCHED_FIFO priority of the RCU per-CPU
kthreads (rcuc/N). This value is also used for
the priority of the RCU boost threads (rcub/N)
and for the RCU grace-period kthreads (rcu_bh,
rcu_preempt, and rcu_sched). If RCU_BOOST is
set, valid values are 1-99 and the default is 1
(the least-favored priority). Otherwise, when
RCU_BOOST is not set, valid values are 0-99 and
the default is zero (non-realtime operation).
rcutree.rcu_nocb_leader_stride= [KNL]
Set the number of NOCB kthread groups, which

34
Documentation/kernel-per-CPU-kthreads.txt
View File

@ -190,20 +190,24 @@ To reduce its OS jitter, do any of the following:
on each CPU, including cs_dbs_timer() and od_dbs_timer().
WARNING: Please check your CPU specifications to
make sure that this is safe on your particular system.
d. It is not possible to entirely get rid of OS jitter
from vmstat_update() on CONFIG_SMP=y systems, but you
can decrease its frequency by writing a large value
to /proc/sys/vm/stat_interval. The default value is
HZ, for an interval of one second. Of course, larger
values will make your virtual-memory statistics update
more slowly. Of course, you can also run your workload
at a real-time priority, thus preempting vmstat_update(),
d. As of v3.18, Christoph Lameter's on-demand vmstat workers
commit prevents OS jitter due to vmstat_update() on
CONFIG_SMP=y systems. Before v3.18, is not possible
to entirely get rid of the OS jitter, but you can
decrease its frequency by writing a large value to
/proc/sys/vm/stat_interval. The default value is HZ,
for an interval of one second. Of course, larger values
will make your virtual-memory statistics update more
slowly. Of course, you can also run your workload at
a real-time priority, thus preempting vmstat_update(),
but if your workload is CPU-bound, this is a bad idea.
However, there is an RFC patch from Christoph Lameter
(based on an earlier one from Gilad Ben-Yossef) that
reduces or even eliminates vmstat overhead for some
workloads at https://lkml.org/lkml/2013/9/4/379.
e. If running on high-end powerpc servers, build with
e. Boot with "elevator=noop" to avoid workqueue use by
the block layer.
f. If running on high-end powerpc servers, build with
CONFIG_PPC_RTAS_DAEMON=n. This prevents the RTAS
daemon from running on each CPU every second or so.
(This will require editing Kconfig files and will defeat
@ -211,12 +215,12 @@ To reduce its OS jitter, do any of the following:
due to the rtas_event_scan() function.
WARNING: Please check your CPU specifications to
make sure that this is safe on your particular system.
f. If running on Cell Processor, build your kernel with
g. If running on Cell Processor, build your kernel with
CBE_CPUFREQ_SPU_GOVERNOR=n to avoid OS jitter from
spu_gov_work().
WARNING: Please check your CPU specifications to
make sure that this is safe on your particular system.
g. If running on PowerMAC, build your kernel with
h. If running on PowerMAC, build your kernel with
CONFIG_PMAC_RACKMETER=n to disable the CPU-meter,
avoiding OS jitter from rackmeter_do_timer().
@ -258,8 +262,12 @@ Purpose: Detect software lockups on each CPU.
To reduce its OS jitter, do at least one of the following:
1. Build with CONFIG_LOCKUP_DETECTOR=n, which will prevent these
kthreads from being created in the first place.
2. Echo a zero to /proc/sys/kernel/watchdog to disable the
2. Boot with "nosoftlockup=0", which will also prevent these kthreads
from being created. Other related watchdog and softlockup boot
parameters may be found in Documentation/kernel-parameters.txt
and Documentation/watchdog/watchdog-parameters.txt.
3. Echo a zero to /proc/sys/kernel/watchdog to disable the
watchdog timer.
3. Echo a large number of /proc/sys/kernel/watchdog_thresh in
4. Echo a large number of /proc/sys/kernel/watchdog_thresh in
order to reduce the frequency of OS jitter due to the watchdog
timer down to a level that is acceptable for your workload.

42
Documentation/memory-barriers.txt
View File

@ -592,9 +592,9 @@ See also the subsection on "Cache Coherency" for a more thorough example.
CONTROL DEPENDENCIES
--------------------
A control dependency requires a full read memory barrier, not simply a data
dependency barrier to make it work correctly. Consider the following bit of
code:
A load-load control dependency requires a full read memory barrier, not
simply a data dependency barrier to make it work correctly. Consider the
following bit of code:
q = ACCESS_ONCE(a);
if (q) {
@ -615,14 +615,15 @@ case what's actually required is:
}
However, stores are not speculated. This means that ordering -is- provided
in the following example:
for load-store control dependencies, as in the following example:
q = ACCESS_ONCE(a);
if (q) {
ACCESS_ONCE(b) = p;
}
Please note that ACCESS_ONCE() is not optional! Without the
Control dependencies pair normally with other types of barriers.
That said, please note that ACCESS_ONCE() is not optional! Without the
ACCESS_ONCE(), might combine the load from 'a' with other loads from
'a', and the store to 'b' with other stores to 'b', with possible highly
counterintuitive effects on ordering.
@ -813,6 +814,8 @@ In summary:
barrier() can help to preserve your control dependency. Please
see the Compiler Barrier section for more information.
(*) Control dependencies pair normally with other types of barriers.
(*) Control dependencies do -not- provide transitivity. If you
need transitivity, use smp_mb().
@ -823,14 +826,14 @@ SMP BARRIER PAIRING
When dealing with CPU-CPU interactions, certain types of memory barrier should
always be paired. A lack of appropriate pairing is almost certainly an error.
General barriers pair with each other, though they also pair with
most other types of barriers, albeit without transitivity. An acquire
barrier pairs with a release barrier, but both may also pair with other
barriers, including of course general barriers. A write barrier pairs
with a data dependency barrier, an acquire barrier, a release barrier,
a read barrier, or a general barrier. Similarly a read barrier or a
data dependency barrier pairs with a write barrier, an acquire barrier,
a release barrier, or a general barrier:
General barriers pair with each other, though they also pair with most
other types of barriers, albeit without transitivity. An acquire barrier
pairs with a release barrier, but both may also pair with other barriers,
including of course general barriers. A write barrier pairs with a data
dependency barrier, a control dependency, an acquire barrier, a release
barrier, a read barrier, or a general barrier. Similarly a read barrier,
control dependency, or a data dependency barrier pairs with a write
barrier, an acquire barrier, a release barrier, or a general barrier:
CPU 1 CPU 2
=============== ===============
@ -850,6 +853,19 @@ Or:
<data dependency barrier>
y = *x;
Or even:
CPU 1 CPU 2
=============== ===============================
r1 = ACCESS_ONCE(y);
<general barrier>
ACCESS_ONCE(y) = 1; if (r2 = ACCESS_ONCE(x)) {
<implicit control dependency>
ACCESS_ONCE(y) = 1;
}
assert(r1 == 0 || r2 == 0);
Basically, the read barrier always has to be there, even though it can be of
the "weaker" type.

10
Documentation/timers/NO_HZ.txt
View File

@ -158,13 +158,9 @@ not come for free:
to the need to inform kernel subsystems (such as RCU) about
the change in mode.
3. POSIX CPU timers on adaptive-tick CPUs may miss their deadlines
(perhaps indefinitely) because they currently rely on
scheduling-tick interrupts. This will likely be fixed in
one of two ways: (1) Prevent CPUs with POSIX CPU timers from
entering adaptive-tick mode, or (2) Use hrtimers or other
adaptive-ticks-immune mechanism to cause the POSIX CPU timer to
fire properly.
3. POSIX CPU timers prevent CPUs from entering adaptive-tick mode.
Real-time applications needing to take actions based on CPU time
consumption need to use other means of doing so.
4. If there are more perf events pending than the hardware can
accommodate, they are normally round-robined so as to collect

6
arch/blackfin/mach-common/smp.c
View File

@ -413,16 +413,14 @@ int __cpu_disable(void)
return 0;
}
static DECLARE_COMPLETION(cpu_killed);
int __cpu_die(unsigned int cpu)
{
return wait_for_completion_timeout(&cpu_killed, 5000);
return cpu_wait_death(cpu, 5);
}
void cpu_die(void)
{
complete(&cpu_killed);
(void)cpu_report_death();
atomic_dec(&init_mm.mm_users);
atomic_dec(&init_mm.mm_count);

5
arch/metag/kernel/smp.c
View File

@ -261,7 +261,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
}
#ifdef CONFIG_HOTPLUG_CPU
static DECLARE_COMPLETION(cpu_killed);
/*
* __cpu_disable runs on the processor to be shutdown.
@ -299,7 +298,7 @@ int __cpu_disable(void)
*/
void __cpu_die(unsigned int cpu)
{
if (!wait_for_completion_timeout(&cpu_killed, msecs_to_jiffies(1)))
if (!cpu_wait_death(cpu, 1))
pr_err("CPU%u: unable to kill\n", cpu);
}
@ -314,7 +313,7 @@ void cpu_die(void)
local_irq_disable();
idle_task_exit();
complete(&cpu_killed);
(void)cpu_report_death();
asm ("XOR TXENABLE, D0Re0,D0Re0\n");
}

2
arch/x86/include/asm/cpu.h
View File

@ -34,8 +34,6 @@ extern int _debug_hotplug_cpu(int cpu, int action);
#endif
#endif
DECLARE_PER_CPU(int, cpu_state);
int mwait_usable(const struct cpuinfo_x86 *);
#endif /* _ASM_X86_CPU_H */

2
arch/x86/include/asm/smp.h
View File

@ -150,12 +150,12 @@ static inline void arch_send_call_function_ipi_mask(const struct cpumask *mask)
}
void cpu_disable_common(void);
void cpu_die_common(unsigned int cpu);
void native_smp_prepare_boot_cpu(void);
void native_smp_prepare_cpus(unsigned int max_cpus);
void native_smp_cpus_done(unsigned int max_cpus);
int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);
int native_cpu_disable(void);
int common_cpu_die(unsigned int cpu);
void native_cpu_die(unsigned int cpu);
void native_play_dead(void);
void play_dead_common(void);

39
arch/x86/kernel/smpboot.c
View File

@ -77,9 +77,6 @@
#include <asm/realmode.h>
#include <asm/misc.h>
/* State of each CPU */
DEFINE_PER_CPU(int, cpu_state) = { 0 };
/* Number of siblings per CPU package */
int smp_num_siblings = 1;
EXPORT_SYMBOL(smp_num_siblings);
@ -257,7 +254,7 @@ static void notrace start_secondary(void *unused)
lock_vector_lock();
set_cpu_online(smp_processor_id(), true);
unlock_vector_lock();
per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
cpu_set_state_online(smp_processor_id());
x86_platform.nmi_init();
/* enable local interrupts */
@ -948,7 +945,10 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
*/
mtrr_save_state();
per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
/* x86 CPUs take themselves offline, so delayed offline is OK. */
err = cpu_check_up_prepare(cpu);
if (err && err != -EBUSY)
return err;
/* the FPU context is blank, nobody can own it */
__cpu_disable_lazy_restore(cpu);
@ -1191,7 +1191,7 @@ void __init native_smp_prepare_boot_cpu(void)
switch_to_new_gdt(me);
/* already set me in cpu_online_mask in boot_cpu_init() */
cpumask_set_cpu(me, cpu_callout_mask);
per_cpu(cpu_state, me) = CPU_ONLINE;
cpu_set_state_online(me);
}
void __init native_smp_cpus_done(unsigned int max_cpus)
@ -1318,14 +1318,10 @@ static void __ref remove_cpu_from_maps(int cpu)
numa_remove_cpu(cpu);
}
static DEFINE_PER_CPU(struct completion, die_complete);
void cpu_disable_common(void)
{
int cpu = smp_processor_id();
init_completion(&per_cpu(die_complete, smp_processor_id()));
remove_siblinginfo(cpu);
/* It's now safe to remove this processor from the online map */
@ -1349,24 +1345,27 @@ int native_cpu_disable(void)
return 0;
}
void cpu_die_common(unsigned int cpu)
int common_cpu_die(unsigned int cpu)
{
wait_for_completion_timeout(&per_cpu(die_complete, cpu), HZ);
}
int ret = 0;
void native_cpu_die(unsigned int cpu)
{
/* We don't do anything here: idle task is faking death itself. */
cpu_die_common(cpu);
/* They ack this in play_dead() by setting CPU_DEAD */
if (per_cpu(cpu_state, cpu) == CPU_DEAD) {
if (cpu_wait_death(cpu, 5)) {
if (system_state == SYSTEM_RUNNING)
pr_info("CPU %u is now offline\n", cpu);
} else {
pr_err("CPU %u didn't die...\n", cpu);
ret = -1;
}
return ret;
}
void native_cpu_die(unsigned int cpu)
{
common_cpu_die(cpu);
}
void play_dead_common(void)
@ -1375,10 +1374,8 @@ void play_dead_common(void)
reset_lazy_tlbstate();
amd_e400_remove_cpu(raw_smp_processor_id());
mb();
/* Ack it */
__this_cpu_write(cpu_state, CPU_DEAD);
complete(&per_cpu(die_complete, smp_processor_id()));
(void)cpu_report_death();
/*
* With physical CPU hotplug, we should halt the cpu

46
arch/x86/xen/smp.c
View File

@ -90,14 +90,10 @@ static void cpu_bringup(void)
set_cpu_online(cpu, true);
this_cpu_write(cpu_state, CPU_ONLINE);
wmb();
cpu_set_state_online(cpu); /* Implies full memory barrier. */
/* We can take interrupts now: we're officially "up". */
local_irq_enable();
wmb(); /* make sure everything is out */
}
/*
@ -459,7 +455,13 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
xen_setup_timer(cpu);
xen_init_lock_cpu(cpu);
per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
/*
* PV VCPUs are always successfully taken down (see 'while' loop
* in xen_cpu_die()), so -EBUSY is an error.
*/
rc = cpu_check_up_prepare(cpu);
if (rc)
return rc;
/* make sure interrupts start blocked */
per_cpu(xen_vcpu, cpu)->evtchn_upcall_mask = 1;
@ -479,10 +481,8 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle)
rc = HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL);
BUG_ON(rc);
while(per_cpu(cpu_state, cpu) != CPU_ONLINE) {
while (cpu_report_state(cpu) != CPU_ONLINE)
HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
barrier();
}
return 0;
}
@ -511,11 +511,11 @@ static void xen_cpu_die(unsigned int cpu)
schedule_timeout(HZ/10);
}
cpu_die_common(cpu);
xen_smp_intr_free(cpu);
xen_uninit_lock_cpu(cpu);
xen_teardown_timer(cpu);
if (common_cpu_die(cpu) == 0) {
xen_smp_intr_free(cpu);
xen_uninit_lock_cpu(cpu);
xen_teardown_timer(cpu);
}
}
static void xen_play_dead(void) /* used only with HOTPLUG_CPU */
@ -747,6 +747,16 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
{
int rc;
/*
* This can happen if CPU was offlined earlier and
* offlining timed out in common_cpu_die().
*/
if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
xen_smp_intr_free(cpu);
xen_uninit_lock_cpu(cpu);
}
/*
* xen_smp_intr_init() needs to run before native_cpu_up()
* so that IPI vectors are set up on the booting CPU before
@ -768,12 +778,6 @@ static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
return rc;
}
static void xen_hvm_cpu_die(unsigned int cpu)
{
xen_cpu_die(cpu);
native_cpu_die(cpu);
}
void __init xen_hvm_smp_init(void)
{
if (!xen_have_vector_callback)
@ -781,7 +785,7 @@ void __init xen_hvm_smp_init(void)
smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
smp_ops.cpu_up = xen_hvm_cpu_up;
smp_ops.cpu_die = xen_hvm_cpu_die;
smp_ops.cpu_die = xen_cpu_die;
smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
smp_ops.send_call_func_single_ipi = xen_smp_send_call_function_single_ipi;
smp_ops.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu;

14
include/linux/cpu.h
View File

@ -95,6 +95,10 @@ enum {
* Called on the new cpu, just before
* enabling interrupts. Must not sleep,
* must not fail */
#define CPU_DYING_IDLE 0x000B /* CPU (unsigned)v dying, reached
* idle loop. */
#define CPU_BROKEN 0x000C /* CPU (unsigned)v did not die properly,
* perhaps due to preemption. */
/* Used for CPU hotplug events occurring while tasks are frozen due to a suspend
* operation in progress
@ -271,4 +275,14 @@ void arch_cpu_idle_enter(void);
void arch_cpu_idle_exit(void);
void arch_cpu_idle_dead(void);
DECLARE_PER_CPU(bool, cpu_dead_idle);
int cpu_report_state(int cpu);
int cpu_check_up_prepare(int cpu);
void cpu_set_state_online(int cpu);
#ifdef CONFIG_HOTPLUG_CPU
bool cpu_wait_death(unsigned int cpu, int seconds);
bool cpu_report_death(void);
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
#endif /* _LINUX_CPU_H_ */

7
include/linux/lockdep.h
View File

@ -531,8 +531,13 @@ do { \
# define might_lock_read(lock) do { } while (0)
#endif
#ifdef CONFIG_PROVE_RCU
#ifdef CONFIG_LOCKDEP
void lockdep_rcu_suspicious(const char *file, const int line, const char *s);
#else
static inline void
lockdep_rcu_suspicious(const char *file, const int line, const char *s)
{
}
#endif
#endif /* __LINUX_LOCKDEP_H */

40
include/linux/rcupdate.h
View File

@ -48,6 +48,26 @@
extern int rcu_expedited; /* for sysctl */
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */
{
return false;
}
static inline void rcu_expedite_gp(void)
{
}
static inline void rcu_unexpedite_gp(void)
{
}
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_expedited(void); /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
#endif /* #else #ifdef CONFIG_TINY_RCU */
enum rcutorture_type {
RCU_FLAVOR,
RCU_BH_FLAVOR,
@ -195,6 +215,15 @@ void call_rcu_sched(struct rcu_head *head,
void synchronize_sched(void);
/*
* Structure allowing asynchronous waiting on RCU.
*/
struct rcu_synchronize {
struct rcu_head head;
struct completion completion;
};
void wakeme_after_rcu(struct rcu_head *head);
/**
* call_rcu_tasks() - Queue an RCU for invocation task-based grace period
* @head: structure to be used for queueing the RCU updates.
@ -258,6 +287,7 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
void rcu_init(void);
void rcu_end_inkernel_boot(void);
void rcu_sched_qs(void);
void rcu_bh_qs(void);
void rcu_check_callbacks(int user);
@ -266,6 +296,8 @@ void rcu_idle_enter(void);
void rcu_idle_exit(void);
void rcu_irq_enter(void);
void rcu_irq_exit(void);
int rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu);
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);
@ -720,7 +752,7 @@ static inline void rcu_preempt_sleep_check(void)
* annotated as __rcu.
*/
#define rcu_dereference_check(p, c) \
__rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu)
__rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu)
/**
* rcu_dereference_bh_check() - rcu_dereference_bh with debug checking
@ -730,7 +762,7 @@ static inline void rcu_preempt_sleep_check(void)
* This is the RCU-bh counterpart to rcu_dereference_check().
*/
#define rcu_dereference_bh_check(p, c) \
__rcu_dereference_check((p), rcu_read_lock_bh_held() || (c), __rcu)
__rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu)
/**
* rcu_dereference_sched_check() - rcu_dereference_sched with debug checking
@ -740,7 +772,7 @@ static inline void rcu_preempt_sleep_check(void)
* This is the RCU-sched counterpart to rcu_dereference_check().
*/
#define rcu_dereference_sched_check(p, c) \
__rcu_dereference_check((p), rcu_read_lock_sched_held() || (c), \
__rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \
__rcu)
#define rcu_dereference_raw(p) rcu_dereference_check(p, 1) /*@@@ needed? @@@*/
@ -933,9 +965,9 @@ static inline void rcu_read_unlock(void)
{
rcu_lockdep_assert(rcu_is_watching(),
"rcu_read_unlock() used illegally while idle");
rcu_lock_release(&rcu_lock_map);
__release(RCU);
__rcu_read_unlock();
rcu_lock_release(&rcu_lock_map); /* Keep acq info for rls diags. */
}
/**

2
include/linux/srcu.h
View File

@ -182,7 +182,7 @@ static inline int srcu_read_lock_held(struct srcu_struct *sp)
* lockdep_is_held() calls.
*/
#define srcu_dereference_check(p, sp, c) \
__rcu_dereference_check((p), srcu_read_lock_held(sp) || (c), __rcu)
__rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu)
/**
* srcu_dereference - fetch SRCU-protected pointer for later dereferencing

13
init/Kconfig
View File

@ -791,6 +791,19 @@ config RCU_NOCB_CPU_ALL
endchoice
config RCU_EXPEDITE_BOOT
bool
default n
help
This option enables expedited grace periods at boot time,
as if rcu_expedite_gp() had been invoked early in boot.
The corresponding rcu_unexpedite_gp() is invoked from
rcu_end_inkernel_boot(), which is intended to be invoked
at the end of the kernel-only boot sequence, just before
init is exec'ed.
Accept the default if unsure.
endmenu # "RCU Subsystem"
config BUILD_BIN2C

4
kernel/cpu.c
View File

@ -408,8 +408,10 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
*
* Wait for the stop thread to go away.
*/
while (!idle_cpu(cpu))
while (!per_cpu(cpu_dead_idle, cpu))
cpu_relax();
smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
per_cpu(cpu_dead_idle, cpu) = false;
/* This actually kills the CPU. */
__cpu_die(cpu);

27
kernel/rcu/rcutorture.c
View File

@ -853,6 +853,8 @@ rcu_torture_fqs(void *arg)
static int
rcu_torture_writer(void *arg)
{
bool can_expedite = !rcu_gp_is_expedited();
int expediting = 0;
unsigned long gp_snap;
bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
bool gp_sync1 = gp_sync;
@ -865,9 +867,15 @@ rcu_torture_writer(void *arg)
int nsynctypes = 0;
VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
pr_alert("%s" TORTURE_FLAG
" Grace periods expedited from boot/sysfs for %s,\n",
torture_type, cur_ops->name);
pr_alert("%s" TORTURE_FLAG
" Testing of dynamic grace-period expediting diabled.\n",
torture_type);
/* Initialize synctype[] array. If none set, take default. */
if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync)
if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1)
gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync)
synctype[nsynctypes++] = RTWS_COND_GET;
@ -949,9 +957,26 @@ rcu_torture_writer(void *arg)
}
}
rcutorture_record_progress(++rcu_torture_current_version);
/* Cycle through nesting levels of rcu_expedite_gp() calls. */
if (can_expedite &&
!(torture_random(&rand) & 0xff & (!!expediting - 1))) {
WARN_ON_ONCE(expediting == 0 && rcu_gp_is_expedited());
if (expediting >= 0)
rcu_expedite_gp();
else
rcu_unexpedite_gp();
if (++expediting > 3)
expediting = -expediting;
}
rcu_torture_writer_state = RTWS_STUTTER;
stutter_wait("rcu_torture_writer");
} while (!torture_must_stop());
/* Reset expediting back to unexpedited. */
if (expediting > 0)
expediting = -expediting;
while (can_expedite && expediting++ < 0)
rcu_unexpedite_gp();
WARN_ON_ONCE(can_expedite && rcu_gp_is_expedited());
rcu_torture_writer_state = RTWS_STOPPING;
torture_kthread_stopping("rcu_torture_writer");
return 0;

19
kernel/rcu/srcu.c
View File

@ -402,23 +402,6 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *head,
}
EXPORT_SYMBOL_GPL(call_srcu);
struct rcu_synchronize {
struct rcu_head head;
struct completion completion;
};
/*
* Awaken the corresponding synchronize_srcu() instance now that a
* grace period has elapsed.
*/
static void wakeme_after_rcu(struct rcu_head *head)
{
struct rcu_synchronize *rcu;
rcu = container_of(head, struct rcu_synchronize, head);
complete(&rcu->completion);
}
static void srcu_advance_batches(struct srcu_struct *sp, int trycount);
static void srcu_reschedule(struct srcu_struct *sp);
@ -507,7 +490,7 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
*/
void synchronize_srcu(struct srcu_struct *sp)
{
__synchronize_srcu(sp, rcu_expedited
__synchronize_srcu(sp, rcu_gp_is_expedited()
? SYNCHRONIZE_SRCU_EXP_TRYCOUNT
: SYNCHRONIZE_SRCU_TRYCOUNT);
}

14
kernel/rcu/tiny.c
View File

@ -103,8 +103,7 @@ EXPORT_SYMBOL(__rcu_is_watching);
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
RCU_TRACE(reset_cpu_stall_ticks(rcp));
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
if (rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
return 1;
}
@ -169,17 +168,6 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
unsigned long flags;
RCU_TRACE(int cb_count = 0);
/* If no RCU callbacks ready to invoke, just return. */
if (&rcp->rcucblist == rcp->donetail) {
RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));
RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
!!ACCESS_ONCE(rcp->rcucblist),
need_resched(),
is_idle_task(current),
false));
return;
}
/* Move the ready-to-invoke callbacks to a local list. */
local_irq_save(flags);
RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1));

437
kernel/rcu/tree.c
View File

@ -91,8 +91,10 @@ static const char *tp_##sname##_varname __used __tracepoint_string = sname##_var
#define RCU_STATE_INITIALIZER(sname, sabbr, cr) \
DEFINE_RCU_TPS(sname) \
DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data); \
struct rcu_state sname##_state = { \
.level = { &sname##_state.node[0] }, \
.rda = &sname##_data, \
.call = cr, \
.fqs_state = RCU_GP_IDLE, \
.gpnum = 0UL - 300UL, \
@ -101,11 +103,9 @@ struct rcu_state sname##_state = { \
.orphan_nxttail = &sname##_state.orphan_nxtlist, \
.orphan_donetail = &sname##_state.orphan_donelist, \
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.onoff_mutex = __MUTEX_INITIALIZER(sname##_state.onoff_mutex), \
.name = RCU_STATE_NAME(sname), \
.abbr = sabbr, \
}; \
DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data)
}
RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
@ -152,6 +152,8 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
*/
static int rcu_scheduler_fully_active __read_mostly;
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf);
static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf);
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
static void invoke_rcu_core(void);
static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
@ -160,6 +162,12 @@ static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO;
module_param(kthread_prio, int, 0644);
/* Delay in jiffies for grace-period initialization delays. */
static int gp_init_delay = IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_INIT)
? CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY
: 0;
module_param(gp_init_delay, int, 0644);
/*
* Track the rcutorture test sequence number and the update version
* number within a given test. The rcutorture_testseq is incremented
@ -172,6 +180,17 @@ module_param(kthread_prio, int, 0644);
unsigned long rcutorture_testseq;
unsigned long rcutorture_vernum;
/*
* Compute the mask of online CPUs for the specified rcu_node structure.
* This will not be stable unless the rcu_node structure's ->lock is
* held, but the bit corresponding to the current CPU will be stable
* in most contexts.
*/
unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
{
return ACCESS_ONCE(rnp->qsmaskinitnext);
}
/*
* Return true if an RCU grace period is in progress. The ACCESS_ONCE()s
* permit this function to be invoked without holding the root rcu_node
@ -292,10 +311,10 @@ void rcu_note_context_switch(void)
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
/*
* Register a quiesecent state for all RCU flavors. If there is an
* Register a quiescent state for all RCU flavors. If there is an
* emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
* dyntick-idle quiescent state visible to other CPUs (but only for those
* RCU flavors in desparate need of a quiescent state, which will normally
* RCU flavors in desperate need of a quiescent state, which will normally
* be none of them). Either way, do a lightweight quiescent state for
* all RCU flavors.
*/
@ -409,6 +428,15 @@ void rcu_bh_force_quiescent_state(void)
}
EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
/*
* Force a quiescent state for RCU-sched.
*/
void rcu_sched_force_quiescent_state(void)
{
force_quiescent_state(&rcu_sched_state);
}
EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
/*
* Show the state of the grace-period kthreads.
*/
@ -482,15 +510,6 @@ void rcutorture_record_progress(unsigned long vernum)
}
EXPORT_SYMBOL_GPL(rcutorture_record_progress);
/*
* Force a quiescent state for RCU-sched.
*/
void rcu_sched_force_quiescent_state(void)
{
force_quiescent_state(&rcu_sched_state);
}
EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
/*
* Does the CPU have callbacks ready to be invoked?
*/
@ -954,7 +973,7 @@ bool rcu_lockdep_current_cpu_online(void)
preempt_disable();
rdp = this_cpu_ptr(&rcu_sched_data);
rnp = rdp->mynode;
ret = (rdp->grpmask & rnp->qsmaskinit) ||
ret = (rdp->grpmask & rcu_rnp_online_cpus(rnp)) ||
!rcu_scheduler_fully_active;
preempt_enable();
return ret;
@ -1196,9 +1215,10 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gpnum)
} else {
j = jiffies;
gpa = ACCESS_ONCE(rsp->gp_activity);
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld\n",
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",
rsp->name, j - gpa, j, gpa,
jiffies_till_next_fqs);
jiffies_till_next_fqs,
rcu_get_root(rsp)->qsmask);
/* In this case, the current CPU might be at fault. */
sched_show_task(current);
}
@ -1327,18 +1347,28 @@ void rcu_cpu_stall_reset(void)
ACCESS_ONCE(rsp->jiffies_stall) = jiffies + ULONG_MAX / 2;
}
/*
* Initialize the specified rcu_data structure's default callback list
* to empty. The default callback list is the one that is not used by
* no-callbacks CPUs.
*/
static void init_default_callback_list(struct rcu_data *rdp)
{
int i;
rdp->nxtlist = NULL;
for (i = 0; i < RCU_NEXT_SIZE; i++)
rdp->nxttail[i] = &rdp->nxtlist;
}
/*
* Initialize the specified rcu_data structure's callback list to empty.
*/
static void init_callback_list(struct rcu_data *rdp)
{
int i;
if (init_nocb_callback_list(rdp))
return;
rdp->nxtlist = NULL;
for (i = 0; i < RCU_NEXT_SIZE; i++)
rdp->nxttail[i] = &rdp->nxtlist;
init_default_callback_list(rdp);
}
/*
@ -1703,11 +1733,11 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
*/
static int rcu_gp_init(struct rcu_state *rsp)
{
unsigned long oldmask;
struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
ACCESS_ONCE(rsp->gp_activity) = jiffies;
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
if (!ACCESS_ONCE(rsp->gp_flags)) {
@ -1733,9 +1763,54 @@ static int rcu_gp_init(struct rcu_state *rsp)
trace_rcu_grace_period(rsp->name, rsp->gpnum, TPS("start"));
raw_spin_unlock_irq(&rnp->lock);
/* Exclude any concurrent CPU-hotplug operations. */
mutex_lock(&rsp->onoff_mutex);
smp_mb__after_unlock_lock(); /* ->gpnum increment before GP! */
/*
* Apply per-leaf buffered online and offline operations to the
* rcu_node tree. Note that this new grace period need not wait
* for subsequent online CPUs, and that quiescent-state forcing
* will handle subsequent offline CPUs.
*/
rcu_for_each_leaf_node(rsp, rnp) {
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
!rnp->wait_blkd_tasks) {
/* Nothing to do on this leaf rcu_node structure. */
raw_spin_unlock_irq(&rnp->lock);
continue;
}
/* Record old state, apply changes to ->qsmaskinit field. */
oldmask = rnp->qsmaskinit;
rnp->qsmaskinit = rnp->qsmaskinitnext;
/* If zero-ness of ->qsmaskinit changed, propagate up tree. */
if (!oldmask != !rnp->qsmaskinit) {
if (!oldmask) /* First online CPU for this rcu_node. */
rcu_init_new_rnp(rnp);
else if (rcu_preempt_has_tasks(rnp)) /* blocked tasks */
rnp->wait_blkd_tasks = true;
else /* Last offline CPU and can propagate. */
rcu_cleanup_dead_rnp(rnp);
}
/*
* If all waited-on tasks from prior grace period are
* done, and if all this rcu_node structure's CPUs are
* still offline, propagate up the rcu_node tree and
* clear ->wait_blkd_tasks. Otherwise, if one of this
* rcu_node structure's CPUs has since come back online,
* simply clear ->wait_blkd_tasks (but rcu_cleanup_dead_rnp()
* checks for this, so just call it unconditionally).
*/
if (rnp->wait_blkd_tasks &&
(!rcu_preempt_has_tasks(rnp) ||
rnp->qsmaskinit)) {
rnp->wait_blkd_tasks = false;
rcu_cleanup_dead_rnp(rnp);
}
raw_spin_unlock_irq(&rnp->lock);
}
/*
* Set the quiescent-state-needed bits in all the rcu_node
@ -1757,8 +1832,8 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
ACCESS_ONCE(rnp->gpnum) = rsp->gpnum;
WARN_ON_ONCE(rnp->completed != rsp->completed);
ACCESS_ONCE(rnp->completed) = rsp->completed;
if (WARN_ON_ONCE(rnp->completed != rsp->completed))
ACCESS_ONCE(rnp->completed) = rsp->completed;
if (rnp == rdp->mynode)
(void)__note_gp_changes(rsp, rnp, rdp);
rcu_preempt_boost_start_gp(rnp);
@ -1768,9 +1843,12 @@ static int rcu_gp_init(struct rcu_state *rsp)
raw_spin_unlock_irq(&rnp->lock);
cond_resched_rcu_qs();
ACCESS_ONCE(rsp->gp_activity) = jiffies;
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_SLOW_INIT) &&
gp_init_delay > 0 &&
!(rsp->gpnum % (rcu_num_nodes * 10)))
schedule_timeout_uninterruptible(gp_init_delay);
}
mutex_unlock(&rsp->onoff_mutex);
return 1;
}
@ -1798,7 +1876,7 @@ static int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
fqs_state = RCU_FORCE_QS;
} else {
/* Handle dyntick-idle and offline CPUs. */
isidle = false;
isidle = true;
force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj);
}
/* Clear flag to prevent immediate re-entry. */
@ -1852,6 +1930,8 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
rcu_for_each_node_breadth_first(rsp, rnp) {
raw_spin_lock_irq(&rnp->lock);
smp_mb__after_unlock_lock();
WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp));
WARN_ON_ONCE(rnp->qsmask);
ACCESS_ONCE(rnp->completed) = rsp->gpnum;
rdp = this_cpu_ptr(rsp->rda);
if (rnp == rdp->mynode)
@ -1895,6 +1975,7 @@ static int __noreturn rcu_gp_kthread(void *arg)
struct rcu_state *rsp = arg;
struct rcu_node *rnp = rcu_get_root(rsp);
rcu_bind_gp_kthread();
for (;;) {
/* Handle grace-period start. */
@ -2062,25 +2143,32 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
* Similar to rcu_report_qs_rdp(), for which it is a helper function.
* Allows quiescent states for a group of CPUs to be reported at one go
* to the specified rcu_node structure, though all the CPUs in the group
* must be represented by the same rcu_node structure (which need not be
* a leaf rcu_node structure, though it often will be). That structure's
* lock must be held upon entry, and it is released before return.
* must be represented by the same rcu_node structure (which need not be a
* leaf rcu_node structure, though it often will be). The gps parameter
* is the grace-period snapshot, which means that the quiescent states
* are valid only if rnp->gpnum is equal to gps. That structure's lock
* must be held upon entry, and it is released before return.
*/
static void
rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
struct rcu_node *rnp, unsigned long flags)
struct rcu_node *rnp, unsigned long gps, unsigned long flags)
__releases(rnp->lock)
{
unsigned long oldmask = 0;
struct rcu_node *rnp_c;
/* Walk up the rcu_node hierarchy. */
for (;;) {
if (!(rnp->qsmask & mask)) {
if (!(rnp->qsmask & mask) || rnp->gpnum != gps) {
/* Our bit has already been cleared, so done. */
/*
* Our bit has already been cleared, or the
* relevant grace period is already over, so done.
*/
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
rnp->qsmask &= ~mask;
trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
mask, rnp->qsmask, rnp->level,
@ -2104,7 +2192,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
rnp = rnp->parent;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
WARN_ON_ONCE(rnp_c->qsmask);
oldmask = rnp_c->qsmask;
}
/*
@ -2115,6 +2203,46 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */
}
/*
* Record a quiescent state for all tasks that were previously queued
* on the specified rcu_node structure and that were blocking the current
* RCU grace period. The caller must hold the specified rnp->lock with
* irqs disabled, and this lock is released upon return, but irqs remain
* disabled.
*/
static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
unsigned long gps;
unsigned long mask;
struct rcu_node *rnp_p;
if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p ||
rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return; /* Still need more quiescent states! */
}
rnp_p = rnp->parent;
if (rnp_p == NULL) {
/*
* Only one rcu_node structure in the tree, so don't
* try to report up to its nonexistent parent!
*/
rcu_report_qs_rsp(rsp, flags);
return;
}
/* Report up the rest of the hierarchy, tracking current ->gpnum. */
gps = rnp->gpnum;
mask = rnp->grpmask;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock();
rcu_report_qs_rnp(mask, rsp, rnp_p, gps, flags);
}
/*
* Record a quiescent state for the specified CPU to that CPU's rcu_data
* structure. This must be either called from the specified CPU, or
@ -2163,7 +2291,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
*/
needwake = rcu_accelerate_cbs(rsp, rnp, rdp);
rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
/* ^^^ Released rnp->lock */
if (needwake)
rcu_gp_kthread_wake(rsp);
}
@ -2256,8 +2385,12 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
}
/* Finally, initialize the rcu_data structure's list to empty. */
/*
* Finally, initialize the rcu_data structure's list to empty and
* disallow further callbacks on this CPU.
*/
init_callback_list(rdp);
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
}
/*
@ -2355,6 +2488,7 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock(); /* GP memory ordering. */
rnp->qsmaskinit &= ~mask;
rnp->qsmask &= ~mask;
if (rnp->qsmaskinit) {
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
return;
@ -2363,6 +2497,26 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
}
}
/*
* The CPU is exiting the idle loop into the arch_cpu_idle_dead()
* function. We now remove it from the rcu_node tree's ->qsmaskinit
* bit masks.
*/
static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
unsigned long mask;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
mask = rdp->grpmask;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */
rnp->qsmaskinitnext &= ~mask;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/*
* The CPU has been completely removed, and some other CPU is reporting
* this fact from process context. Do the remainder of the cleanup,
@ -2379,29 +2533,15 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);
/* Exclude any attempts to start a new grace period. */
mutex_lock(&rsp->onoff_mutex);
raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
/* Orphan the dead CPU's callbacks, and adopt them if appropriate. */
raw_spin_lock_irqsave(&rsp->orphan_lock, flags);
rcu_send_cbs_to_orphanage(cpu, rsp, rnp, rdp);
rcu_adopt_orphan_cbs(rsp, flags);
raw_spin_unlock_irqrestore(&rsp->orphan_lock, flags);
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock(); /* Enforce GP memory-order guarantee. */
rnp->qsmaskinit &= ~rdp->grpmask;
if (rnp->qsmaskinit == 0 && !rcu_preempt_has_tasks(rnp))
rcu_cleanup_dead_rnp(rnp);
rcu_report_qs_rnp(rdp->grpmask, rsp, rnp, flags); /* Rlses rnp->lock. */
WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
"rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
cpu, rdp->qlen, rdp->nxtlist);
init_callback_list(rdp);
/* Disallow further callbacks on this CPU. */
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
mutex_unlock(&rsp->onoff_mutex);
}
#else /* #ifdef CONFIG_HOTPLUG_CPU */
@ -2414,6 +2554,10 @@ static void __maybe_unused rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf)
{
}
static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
{
}
static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
}
@ -2589,26 +2733,47 @@ static void force_qs_rnp(struct rcu_state *rsp,
return;
}
if (rnp->qsmask == 0) {
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
continue;
if (rcu_state_p == &rcu_sched_state ||
rsp != rcu_state_p ||
rcu_preempt_blocked_readers_cgp(rnp)) {
/*
* No point in scanning bits because they
* are all zero. But we might need to
* priority-boost blocked readers.
*/
rcu_initiate_boost(rnp, flags);
/* rcu_initiate_boost() releases rnp->lock */
continue;
}
if (rnp->parent &&
(rnp->parent->qsmask & rnp->grpmask)) {
/*
* Race between grace-period
* initialization and task exiting RCU
* read-side critical section: Report.
*/
rcu_report_unblock_qs_rnp(rsp, rnp, flags);
/* rcu_report_unblock_qs_rnp() rlses ->lock */
continue;
}
}
cpu = rnp->grplo;
bit = 1;
for (; cpu <= rnp->grphi; cpu++, bit <<= 1) {
if ((rnp->qsmask & bit) != 0) {
if ((rnp->qsmaskinit & bit) != 0)
*isidle = false;
if ((rnp->qsmaskinit & bit) == 0)
*isidle = false; /* Pending hotplug. */
if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj))
mask |= bit;
}
}
if (mask != 0) {
/* rcu_report_qs_rnp() releases rnp->lock. */
rcu_report_qs_rnp(mask, rsp, rnp, flags);
continue;
/* Idle/offline CPUs, report (releases rnp->lock. */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags);
} else {
/* Nothing to do here, so just drop the lock. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
}
@ -2741,7 +2906,7 @@ static void __call_rcu_core(struct rcu_state *rsp, struct rcu_data *rdp,
* If called from an extended quiescent state, invoke the RCU
* core in order to force a re-evaluation of RCU's idleness.
*/
if (!rcu_is_watching() && cpu_online(smp_processor_id()))
if (!rcu_is_watching())
invoke_rcu_core();
/* If interrupts were disabled or CPU offline, don't invoke RCU core. */
@ -2827,11 +2992,22 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
if (cpu != -1)
rdp = per_cpu_ptr(rsp->rda, cpu);
offline = !__call_rcu_nocb(rdp, head, lazy, flags);
WARN_ON_ONCE(offline);
/* _call_rcu() is illegal on offline CPU; leak the callback. */
local_irq_restore(flags);
return;
if (likely(rdp->mynode)) {
/* Post-boot, so this should be for a no-CBs CPU. */
offline = !__call_rcu_nocb(rdp, head, lazy, flags);
WARN_ON_ONCE(offline);
/* Offline CPU, _call_rcu() illegal, leak callback. */
local_irq_restore(flags);
return;
}
/*
* Very early boot, before rcu_init(). Initialize if needed
* and then drop through to queue the callback.
*/
BUG_ON(cpu != -1);
WARN_ON_ONCE(!rcu_is_watching());
if (!likely(rdp->nxtlist))
init_default_callback_list(rdp);
}
ACCESS_ONCE(rdp->qlen) = rdp->qlen + 1;
if (lazy)
@ -2954,7 +3130,7 @@ void synchronize_sched(void)
"Illegal synchronize_sched() in RCU-sched read-side critical section");
if (rcu_blocking_is_gp())
return;
if (rcu_expedited)
if (rcu_gp_is_expedited())
synchronize_sched_expedited();
else
wait_rcu_gp(call_rcu_sched);
@ -2981,7 +3157,7 @@ void synchronize_rcu_bh(void)
"Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
if (rcu_blocking_is_gp())
return;
if (rcu_expedited)
if (rcu_gp_is_expedited())
synchronize_rcu_bh_expedited();
else
wait_rcu_gp(call_rcu_bh);
@ -3517,6 +3693,28 @@ void rcu_barrier_sched(void)
}
EXPORT_SYMBOL_GPL(rcu_barrier_sched);
/*
* Propagate ->qsinitmask bits up the rcu_node tree to account for the
* first CPU in a given leaf rcu_node structure coming online. The caller
* must hold the corresponding leaf rcu_node ->lock with interrrupts
* disabled.
*/
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
{
long mask;
struct rcu_node *rnp = rnp_leaf;
for (;;) {
mask = rnp->grpmask;
rnp = rnp->parent;
if (rnp == NULL)
return;
raw_spin_lock(&rnp->lock); /* Interrupts already disabled. */
rnp->qsmaskinit |= mask;
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
}
}
/*
* Do boot-time initialization of a CPU's per-CPU RCU data.
*/
@ -3553,49 +3751,37 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
struct rcu_node *rnp = rcu_get_root(rsp);
/* Exclude new grace periods. */
mutex_lock(&rsp->onoff_mutex);
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
rdp->beenonline = 1; /* We have now been online. */
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->blimit = blimit;
init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
if (!rdp->nxtlist)
init_callback_list(rdp); /* Re-enable callbacks on this CPU. */
rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
rcu_sysidle_init_percpu_data(rdp->dynticks);
atomic_set(&rdp->dynticks->dynticks,
(atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
/* Add CPU to rcu_node bitmasks. */
/*
* Add CPU to leaf rcu_node pending-online bitmask. Any needed
* propagation up the rcu_node tree will happen at the beginning
* of the next grace period.
*/
rnp = rdp->mynode;
mask = rdp->grpmask;
do {
/* Exclude any attempts to start a new GP on small systems. */
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
rnp->qsmaskinit |= mask;
mask = rnp->grpmask;
if (rnp == rdp->mynode) {
/*
* If there is a grace period in progress, we will
* set up to wait for it next time we run the
* RCU core code.
*/
rdp->gpnum = rnp->completed;
rdp->completed = rnp->completed;
rdp->passed_quiesce = 0;
rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
rdp->qs_pending = 0;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
}
raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
rnp = rnp->parent;
} while (rnp != NULL && !(rnp->qsmaskinit & mask));
local_irq_restore(flags);
mutex_unlock(&rsp->onoff_mutex);
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock();
rnp->qsmaskinitnext |= mask;
rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
rdp->completed = rnp->completed;
rdp->passed_quiesce = false;
rdp->rcu_qs_ctr_snap = __this_cpu_read(rcu_qs_ctr);
rdp->qs_pending = false;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
static void rcu_prepare_cpu(int cpu)
@ -3609,15 +3795,14 @@ static void rcu_prepare_cpu(int cpu)
/*
* Handle CPU online/offline notification events.
*/
static int rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
int rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
long cpu = (long)hcpu;
struct rcu_data *rdp = per_cpu_ptr(rcu_state_p->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
struct rcu_state *rsp;
trace_rcu_utilization(TPS("Start CPU hotplug"));
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
@ -3637,6 +3822,11 @@ static int rcu_cpu_notify(struct notifier_block *self,
for_each_rcu_flavor(rsp)
rcu_cleanup_dying_cpu(rsp);
break;
case CPU_DYING_IDLE:
for_each_rcu_flavor(rsp) {
rcu_cleanup_dying_idle_cpu(cpu, rsp);
}
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
case CPU_UP_CANCELED:
@ -3649,7 +3839,6 @@ static int rcu_cpu_notify(struct notifier_block *self,
default:
break;
}
trace_rcu_utilization(TPS("End CPU hotplug"));
return NOTIFY_OK;
}
@ -3660,11 +3849,12 @@ static int rcu_pm_notify(struct notifier_block *self,
case PM_HIBERNATION_PREPARE:
case PM_SUSPEND_PREPARE:
if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
rcu_expedited = 1;
rcu_expedite_gp();
break;
case PM_POST_HIBERNATION:
case PM_POST_SUSPEND:
rcu_expedited = 0;
if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */
rcu_unexpedite_gp();
break;
default:
break;
@ -3734,30 +3924,26 @@ void rcu_scheduler_starting(void)
* Compute the per-level fanout, either using the exact fanout specified
* or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT.
*/
#ifdef CONFIG_RCU_FANOUT_EXACT
static void __init rcu_init_levelspread(struct rcu_state *rsp)
{
int i;
rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
for (i = rcu_num_lvls - 2; i >= 0; i--)
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
}
#else /* #ifdef CONFIG_RCU_FANOUT_EXACT */
static void __init rcu_init_levelspread(struct rcu_state *rsp)
{
int ccur;
int cprv;
int i;
if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT)) {
rsp->levelspread[rcu_num_lvls - 1] = rcu_fanout_leaf;
for (i = rcu_num_lvls - 2; i >= 0; i--)
rsp->levelspread[i] = CONFIG_RCU_FANOUT;
} else {
int ccur;
int cprv;
cprv = nr_cpu_ids;
for (i = rcu_num_lvls - 1; i >= 0; i--) {
ccur = rsp->levelcnt[i];
rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
cprv = ccur;
cprv = nr_cpu_ids;
for (i = rcu_num_lvls - 1; i >= 0; i--) {
ccur = rsp->levelcnt[i];
rsp->levelspread[i] = (cprv + ccur - 1) / ccur;
cprv = ccur;
}
}
}
#endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */
/*
* Helper function for rcu_init() that initializes one rcu_state structure.
@ -3833,7 +4019,6 @@ static void __init rcu_init_one(struct rcu_state *rsp,
}
}
rsp->rda = rda;
init_waitqueue_head(&rsp->gp_wq);
rnp = rsp->level[rcu_num_lvls - 1];
for_each_possible_cpu(i) {
@ -3926,6 +4111,8 @@ void __init rcu_init(void)
{
int cpu;
rcu_early_boot_tests();
rcu_bootup_announce();
rcu_init_geometry();
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
@ -3942,8 +4129,6 @@ void __init rcu_init(void)
pm_notifier(rcu_pm_notify, 0);
for_each_online_cpu(cpu)
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
rcu_early_boot_tests();
}
#include "tree_plugin.h"

11
kernel/rcu/tree.h
View File

@ -141,12 +141,20 @@ struct rcu_node {
/* complete (only for PREEMPT_RCU). */
unsigned long qsmaskinit;
/* Per-GP initial value for qsmask & expmask. */
/* Initialized from ->qsmaskinitnext at the */
/* beginning of each grace period. */
unsigned long qsmaskinitnext;
/* Online CPUs for next grace period. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
int grphi; /* highest-numbered CPU or group here. */
u8 grpnum; /* CPU/group number for next level up. */
u8 level; /* root is at level 0. */
bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
/* exit RCU read-side critical sections */
/* before propagating offline up the */
/* rcu_node tree? */
struct rcu_node *parent;
struct list_head blkd_tasks;
/* Tasks blocked in RCU read-side critical */
@ -448,8 +456,6 @@ struct rcu_state {
long qlen; /* Total number of callbacks. */
/* End of fields guarded by orphan_lock. */
struct mutex onoff_mutex; /* Coordinate hotplug & GPs. */
struct mutex barrier_mutex; /* Guards barrier fields. */
atomic_t barrier_cpu_count; /* # CPUs waiting on. */
struct completion barrier_completion; /* Wake at barrier end. */
@ -559,6 +565,7 @@ static void rcu_prepare_kthreads(int cpu);
static void rcu_cleanup_after_idle(void);
static void rcu_prepare_for_idle(void);
static void rcu_idle_count_callbacks_posted(void);
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
static void print_cpu_stall_info_begin(void);
static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
static void print_cpu_stall_info_end(void);

267
kernel/rcu/tree_plugin.h
View File

@ -58,38 +58,33 @@ static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
*/
static void __init rcu_bootup_announce_oddness(void)
{
#ifdef CONFIG_RCU_TRACE
pr_info("\tRCU debugfs-based tracing is enabled.\n");
#endif
#if (defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) || (!defined(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32)
pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
CONFIG_RCU_FANOUT);
#endif
#ifdef CONFIG_RCU_FANOUT_EXACT
pr_info("\tHierarchical RCU autobalancing is disabled.\n");
#endif
#ifdef CONFIG_RCU_FAST_NO_HZ
pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
#endif
#ifdef CONFIG_PROVE_RCU
pr_info("\tRCU lockdep checking is enabled.\n");
#endif
#ifdef CONFIG_RCU_TORTURE_TEST_RUNNABLE
pr_info("\tRCU torture testing starts during boot.\n");
#endif
#if defined(CONFIG_RCU_CPU_STALL_INFO)
pr_info("\tAdditional per-CPU info printed with stalls.\n");
#endif
#if NUM_RCU_LVL_4 != 0
pr_info("\tFour-level hierarchy is enabled.\n");
#endif
if (IS_ENABLED(CONFIG_RCU_TRACE))
pr_info("\tRCU debugfs-based tracing is enabled.\n");
if ((IS_ENABLED(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 64) ||
(!IS_ENABLED(CONFIG_64BIT) && CONFIG_RCU_FANOUT != 32))
pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n",
CONFIG_RCU_FANOUT);
if (IS_ENABLED(CONFIG_RCU_FANOUT_EXACT))
pr_info("\tHierarchical RCU autobalancing is disabled.\n");
if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ))
pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
if (IS_ENABLED(CONFIG_PROVE_RCU))
pr_info("\tRCU lockdep checking is enabled.\n");
if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST_RUNNABLE))
pr_info("\tRCU torture testing starts during boot.\n");
if (IS_ENABLED(CONFIG_RCU_CPU_STALL_INFO))
pr_info("\tAdditional per-CPU info printed with stalls.\n");
if (NUM_RCU_LVL_4 != 0)
pr_info("\tFour-level hierarchy is enabled.\n");
if (CONFIG_RCU_FANOUT_LEAF != 16)
pr_info("\tBuild-time adjustment of leaf fanout to %d.\n",
CONFIG_RCU_FANOUT_LEAF);
if (rcu_fanout_leaf != CONFIG_RCU_FANOUT_LEAF)
pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
if (nr_cpu_ids != NR_CPUS)
pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids);
#ifdef CONFIG_RCU_BOOST
pr_info("\tRCU kthread priority: %d.\n", kthread_prio);
#endif
if (IS_ENABLED(CONFIG_RCU_BOOST))
pr_info("\tRCU kthread priority: %d.\n", kthread_prio);
}
#ifdef CONFIG_PREEMPT_RCU
@ -180,7 +175,7 @@ static void rcu_preempt_note_context_switch(void)
* But first, note that the current CPU must still be
* on line!
*/
WARN_ON_ONCE((rdp->grpmask & rnp->qsmaskinit) == 0);
WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0);
WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
if ((rnp->qsmask & rdp->grpmask) && rnp->gp_tasks != NULL) {
list_add(&t->rcu_node_entry, rnp->gp_tasks->prev);
@ -232,43 +227,6 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
return rnp->gp_tasks != NULL;
}
/*
* Record a quiescent state for all tasks that were previously queued
* on the specified rcu_node structure and that were blocking the current
* RCU grace period. The caller must hold the specified rnp->lock with
* irqs disabled, and this lock is released upon return, but irqs remain
* disabled.
*/
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
unsigned long mask;
struct rcu_node *rnp_p;
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return; /* Still need more quiescent states! */
}
rnp_p = rnp->parent;
if (rnp_p == NULL) {
/*
* Either there is only one rcu_node in the tree,
* or tasks were kicked up to root rcu_node due to
* CPUs going offline.
*/
rcu_report_qs_rsp(&rcu_preempt_state, flags);
return;
}
/* Report up the rest of the hierarchy. */
mask = rnp->grpmask;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
raw_spin_lock(&rnp_p->lock); /* irqs already disabled. */
smp_mb__after_unlock_lock();
rcu_report_qs_rnp(mask, &rcu_preempt_state, rnp_p, flags);
}
/*
* Advance a ->blkd_tasks-list pointer to the next entry, instead
* returning NULL if at the end of the list.
@ -300,7 +258,6 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
*/
void rcu_read_unlock_special(struct task_struct *t)
{
bool empty;
bool empty_exp;
bool empty_norm;
bool empty_exp_now;
@ -334,7 +291,13 @@ void rcu_read_unlock_special(struct task_struct *t)
}
/* Hardware IRQ handlers cannot block, complain if they get here. */
if (WARN_ON_ONCE(in_irq() || in_serving_softirq())) {
if (in_irq() || in_serving_softirq()) {
lockdep_rcu_suspicious(__FILE__, __LINE__,
"rcu_read_unlock() from irq or softirq with blocking in critical section!!!\n");
pr_alert("->rcu_read_unlock_special: %#x (b: %d, nq: %d)\n",
t->rcu_read_unlock_special.s,
t->rcu_read_unlock_special.b.blocked,
t->rcu_read_unlock_special.b.need_qs);
local_irq_restore(flags);
return;
}
@ -356,7 +319,6 @@ void rcu_read_unlock_special(struct task_struct *t)
break;
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
}
empty = !rcu_preempt_has_tasks(rnp);
empty_norm = !rcu_preempt_blocked_readers_cgp(rnp);
empty_exp = !rcu_preempted_readers_exp(rnp);
smp_mb(); /* ensure expedited fastpath sees end of RCU c-s. */
@ -376,14 +338,6 @@ void rcu_read_unlock_special(struct task_struct *t)
drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;
#endif /* #ifdef CONFIG_RCU_BOOST */
/*
* If this was the last task on the list, go see if we
* need to propagate ->qsmaskinit bit clearing up the
* rcu_node tree.
*/
if (!empty && !rcu_preempt_has_tasks(rnp))
rcu_cleanup_dead_rnp(rnp);
/*
* If this was the last task on the current list, and if
* we aren't waiting on any CPUs, report the quiescent state.
@ -399,7 +353,8 @@ void rcu_read_unlock_special(struct task_struct *t)
rnp->grplo,
rnp->grphi,
!!rnp->gp_tasks);
rcu_report_unblock_qs_rnp(rnp, flags);
rcu_report_unblock_qs_rnp(&rcu_preempt_state,
rnp, flags);
} else {
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
@ -520,10 +475,6 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
WARN_ON_ONCE(rnp->qsmask);
}
#ifdef CONFIG_HOTPLUG_CPU
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
* Check for a quiescent state from the current CPU. When a task blocks,
* the task is recorded in the corresponding CPU's rcu_node structure,
@ -585,7 +536,7 @@ void synchronize_rcu(void)
"Illegal synchronize_rcu() in RCU read-side critical section");
if (!rcu_scheduler_active)
return;
if (rcu_expedited)
if (rcu_gp_is_expedited())
synchronize_rcu_expedited();
else
wait_rcu_gp(call_rcu);
@ -630,9 +581,6 @@ static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
* recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!)
*
* Most callers will set the "wake" flag, but the task initiating the
* expedited grace period need not wake itself.
*
* Caller must hold sync_rcu_preempt_exp_mutex.
*/
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
@ -667,29 +615,85 @@ static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
/*
* Snapshot the tasks blocking the newly started preemptible-RCU expedited
* grace period for the specified rcu_node structure. If there are no such
* tasks, report it up the rcu_node hierarchy.
* grace period for the specified rcu_node structure, phase 1. If there
* are such tasks, set the ->expmask bits up the rcu_node tree and also
* set the ->expmask bits on the leaf rcu_node structures to tell phase 2
* that work is needed here.
*
* Caller must hold sync_rcu_preempt_exp_mutex and must exclude
* CPU hotplug operations.
* Caller must hold sync_rcu_preempt_exp_mutex.
*/
static void
sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
sync_rcu_preempt_exp_init1(struct rcu_state *rsp, struct rcu_node *rnp)
{
unsigned long flags;
int must_wait = 0;
unsigned long mask;
struct rcu_node *rnp_up;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
WARN_ON_ONCE(rnp->expmask);
WARN_ON_ONCE(rnp->exp_tasks);
if (!rcu_preempt_has_tasks(rnp)) {
/* No blocked tasks, nothing to do. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
} else {
return;
}
/* Call for Phase 2 and propagate ->expmask bits up the tree. */
rnp->expmask = 1;
rnp_up = rnp;
while (rnp_up->parent) {
mask = rnp_up->grpmask;
rnp_up = rnp_up->parent;
if (rnp_up->expmask & mask)
break;
raw_spin_lock(&rnp_up->lock); /* irqs already off */
smp_mb__after_unlock_lock();
rnp_up->expmask |= mask;
raw_spin_unlock(&rnp_up->lock); /* irqs still off */
}
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/*
* Snapshot the tasks blocking the newly started preemptible-RCU expedited
* grace period for the specified rcu_node structure, phase 2. If the
* leaf rcu_node structure has its ->expmask field set, check for tasks.
* If there are some, clear ->expmask and set ->exp_tasks accordingly,
* then initiate RCU priority boosting. Otherwise, clear ->expmask and
* invoke rcu_report_exp_rnp() to clear out the upper-level ->expmask bits,
* enabling rcu_read_unlock_special() to do the bit-clearing.
*
* Caller must hold sync_rcu_preempt_exp_mutex.
*/
static void
sync_rcu_preempt_exp_init2(struct rcu_state *rsp, struct rcu_node *rnp)
{
unsigned long flags;
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
if (!rnp->expmask) {
/* Phase 1 didn't do anything, so Phase 2 doesn't either. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
/* Phase 1 is over. */
rnp->expmask = 0;
/*
* If there are still blocked tasks, set up ->exp_tasks so that
* rcu_read_unlock_special() will wake us and then boost them.
*/
if (rcu_preempt_has_tasks(rnp)) {
rnp->exp_tasks = rnp->blkd_tasks.next;
rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
must_wait = 1;
return;
}
if (!must_wait)
rcu_report_exp_rnp(rsp, rnp, false); /* Don't wake self. */
/* No longer any blocked tasks, so undo bit setting. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
rcu_report_exp_rnp(rsp, rnp, false);
}
/**
@ -706,7 +710,6 @@ sync_rcu_preempt_exp_init(struct rcu_state *rsp, struct rcu_node *rnp)
*/
void synchronize_rcu_expedited(void)
{
unsigned long flags;
struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_preempt_state;
unsigned long snap;
@ -757,19 +760,16 @@ void synchronize_rcu_expedited(void)
/* force all RCU readers onto ->blkd_tasks lists. */
synchronize_sched_expedited();
/* Initialize ->expmask for all non-leaf rcu_node structures. */
rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) {
raw_spin_lock_irqsave(&rnp->lock, flags);
smp_mb__after_unlock_lock();
rnp->expmask = rnp->qsmaskinit;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/* Snapshot current state of ->blkd_tasks lists. */
/*
* Snapshot current state of ->blkd_tasks lists into ->expmask.
* Phase 1 sets bits and phase 2 permits rcu_read_unlock_special()
* to start clearing them. Doing this in one phase leads to
* strange races between setting and clearing bits, so just say "no"!
*/
rcu_for_each_leaf_node(rsp, rnp)
sync_rcu_preempt_exp_init(rsp, rnp);
if (NUM_RCU_NODES > 1)
sync_rcu_preempt_exp_init(rsp, rcu_get_root(rsp));
sync_rcu_preempt_exp_init1(rsp, rnp);
rcu_for_each_leaf_node(rsp, rnp)
sync_rcu_preempt_exp_init2(rsp, rnp);
put_online_cpus();
@ -859,8 +859,6 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Because there is no preemptible RCU, there can be no readers blocked.
*/
@ -869,8 +867,6 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
return false;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
/*
* Because preemptible RCU does not exist, we never have to check for
* tasks blocked within RCU read-side critical sections.
@ -1170,7 +1166,7 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
* Returns zero if all is well, a negated errno otherwise.
*/
static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
struct rcu_node *rnp)
struct rcu_node *rnp)
{
int rnp_index = rnp - &rsp->node[0];
unsigned long flags;
@ -1180,7 +1176,7 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
if (&rcu_preempt_state != rsp)
return 0;
if (!rcu_scheduler_fully_active || rnp->qsmaskinit == 0)
if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0)
return 0;
rsp->boost = 1;
@ -1273,7 +1269,7 @@ static void rcu_cpu_kthread(unsigned int cpu)
static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
{
struct task_struct *t = rnp->boost_kthread_task;
unsigned long mask = rnp->qsmaskinit;
unsigned long mask = rcu_rnp_online_cpus(rnp);
cpumask_var_t cm;
int cpu;
@ -1945,7 +1941,8 @@ static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu)
rhp = ACCESS_ONCE(rdp->nocb_follower_head);
/* Having no rcuo kthread but CBs after scheduler starts is bad! */
if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp) {
if (!ACCESS_ONCE(rdp->nocb_kthread) && rhp &&
rcu_scheduler_fully_active) {
/* RCU callback enqueued before CPU first came online??? */
pr_err("RCU: Never-onlined no-CBs CPU %d has CB %p\n",
cpu, rhp->func);
@ -2392,18 +2389,8 @@ void __init rcu_init_nohz(void)
pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
for_each_rcu_flavor(rsp) {
for_each_cpu(cpu, rcu_nocb_mask) {
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
/*
* If there are early callbacks, they will need
* to be moved to the nocb lists.
*/
WARN_ON_ONCE(rdp->nxttail[RCU_NEXT_TAIL] !=
&rdp->nxtlist &&
rdp->nxttail[RCU_NEXT_TAIL] != NULL);
init_nocb_callback_list(rdp);
}
for_each_cpu(cpu, rcu_nocb_mask)
init_nocb_callback_list(per_cpu_ptr(rsp->rda, cpu));
rcu_organize_nocb_kthreads(rsp);
}
}
@ -2540,6 +2527,16 @@ static bool init_nocb_callback_list(struct rcu_data *rdp)
if (!rcu_is_nocb_cpu(rdp->cpu))
return false;
/* If there are early-boot callbacks, move them to nocb lists. */
if (rdp->nxtlist) {
rdp->nocb_head = rdp->nxtlist;
rdp->nocb_tail = rdp->nxttail[RCU_NEXT_TAIL];
atomic_long_set(&rdp->nocb_q_count, rdp->qlen);
atomic_long_set(&rdp->nocb_q_count_lazy, rdp->qlen_lazy);
rdp->nxtlist = NULL;
rdp->qlen = 0;
rdp->qlen_lazy = 0;
}
rdp->nxttail[RCU_NEXT_TAIL] = NULL;
return true;
}
@ -2763,7 +2760,8 @@ static void rcu_sysidle_exit(int irq)
/*
* Check to see if the current CPU is idle. Note that usermode execution
* does not count as idle. The caller must have disabled interrupts.
* does not count as idle. The caller must have disabled interrupts,
* and must be running on tick_do_timer_cpu.
*/
static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
unsigned long *maxj)
@ -2784,8 +2782,8 @@ static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
if (!*isidle || rdp->rsp != rcu_state_p ||
cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu)
return;
if (rcu_gp_in_progress(rdp->rsp))
WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
/* Verify affinity of current kthread. */
WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu);
/* Pick up current idle and NMI-nesting counter and check. */
cur = atomic_read(&rdtp->dynticks_idle);
@ -3068,11 +3066,10 @@ static void rcu_bind_gp_kthread(void)
return;
#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
cpu = tick_do_timer_cpu;
if (cpu >= 0 && cpu < nr_cpu_ids && raw_smp_processor_id() != cpu)
if (cpu >= 0 && cpu < nr_cpu_ids)
set_cpus_allowed_ptr(current, cpumask_of(cpu));
#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
if (!is_housekeeping_cpu(raw_smp_processor_id()))
housekeeping_affine(current);
housekeeping_affine(current);
#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
}

4
kernel/rcu/tree_trace.c
View File

@ -283,8 +283,8 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
seq_puts(m, "\n");
level = rnp->level;
}
seq_printf(m, "%lx/%lx %c%c>%c %d:%d ^%d ",
rnp->qsmask, rnp->qsmaskinit,
seq_printf(m, "%lx/%lx->%lx %c%c>%c %d:%d ^%d ",
rnp->qsmask, rnp->qsmaskinit, rnp->qsmaskinitnext,
".G"[rnp->gp_tasks != NULL],
".E"[rnp->exp_tasks != NULL],
".T"[!list_empty(&rnp->blkd_tasks)],

72
kernel/rcu/update.c
View File

@ -62,6 +62,63 @@ MODULE_ALIAS("rcupdate");
module_param(rcu_expedited, int, 0);
#ifndef CONFIG_TINY_RCU
static atomic_t rcu_expedited_nesting =
ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
/*
* Should normal grace-period primitives be expedited? Intended for
* use within RCU. Note that this function takes the rcu_expedited
* sysfs/boot variable into account as well as the rcu_expedite_gp()
* nesting. So looping on rcu_unexpedite_gp() until rcu_gp_is_expedited()
* returns false is a -really- bad idea.
*/
bool rcu_gp_is_expedited(void)
{
return rcu_expedited || atomic_read(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_gp_is_expedited);
/**
* rcu_expedite_gp - Expedite future RCU grace periods
*
* After a call to this function, future calls to synchronize_rcu() and
* friends act as the corresponding synchronize_rcu_expedited() function
* had instead been called.
*/
void rcu_expedite_gp(void)
{
atomic_inc(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_expedite_gp);
/**
* rcu_unexpedite_gp - Cancel prior rcu_expedite_gp() invocation
*
* Undo a prior call to rcu_expedite_gp(). If all prior calls to
* rcu_expedite_gp() are undone by a subsequent call to rcu_unexpedite_gp(),
* and if the rcu_expedited sysfs/boot parameter is not set, then all
* subsequent calls to synchronize_rcu() and friends will return to
* their normal non-expedited behavior.
*/
void rcu_unexpedite_gp(void)
{
atomic_dec(&rcu_expedited_nesting);
}
EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
#endif /* #ifndef CONFIG_TINY_RCU */
/*
* Inform RCU of the end of the in-kernel boot sequence.
*/
void rcu_end_inkernel_boot(void)
{
if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
rcu_unexpedite_gp();
}
#ifdef CONFIG_PREEMPT_RCU
/*
@ -199,16 +256,13 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
struct rcu_synchronize {
struct rcu_head head;
struct completion completion;
};
/*
* Awaken the corresponding synchronize_rcu() instance now that a
* grace period has elapsed.
/**
* wakeme_after_rcu() - Callback function to awaken a task after grace period
* @head: Pointer to rcu_head member within rcu_synchronize structure
*
* Awaken the corresponding task now that a grace period has elapsed.
*/
static void wakeme_after_rcu(struct rcu_head *head)
void wakeme_after_rcu(struct rcu_head *head)
{
struct rcu_synchronize *rcu;

9
kernel/sched/idle.c
View File

@ -210,6 +210,8 @@ use_default:
goto exit_idle;
}
DEFINE_PER_CPU(bool, cpu_dead_idle);
/*
* Generic idle loop implementation
*
@ -234,8 +236,13 @@ static void cpu_idle_loop(void)
check_pgt_cache();
rmb();
if (cpu_is_offline(smp_processor_id()))
if (cpu_is_offline(smp_processor_id())) {
rcu_cpu_notify(NULL, CPU_DYING_IDLE,
(void *)(long)smp_processor_id());
smp_mb(); /* all activity before dead. */
this_cpu_write(cpu_dead_idle, true);
arch_cpu_idle_dead();
}
local_irq_disable();
arch_cpu_idle_enter();

156
kernel/smpboot.c
View File

@ -4,6 +4,7 @@
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/smp.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/slab.h>
@ -314,3 +315,158 @@ void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
put_online_cpus();
}
EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
/*
* Called to poll specified CPU's state, for example, when waiting for
* a CPU to come online.
*/
int cpu_report_state(int cpu)
{
return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
}
/*
* If CPU has died properly, set its state to CPU_UP_PREPARE and
* return success. Otherwise, return -EBUSY if the CPU died after
* cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
* if cpu_wait_death() timed out and the CPU still hasn't gotten around
* to dying. In the latter two cases, the CPU might not be set up
* properly, but it is up to the arch-specific code to decide.
* Finally, -EIO indicates an unanticipated problem.
*
* Note that it is permissible to omit this call entirely, as is
* done in architectures that do no CPU-hotplug error checking.
*/
int cpu_check_up_prepare(int cpu)
{
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
return 0;
}
switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
case CPU_POST_DEAD:
/* The CPU died properly, so just start it up again. */
atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
return 0;
case CPU_DEAD_FROZEN:
/*
* Timeout during CPU death, so let caller know.
* The outgoing CPU completed its processing, but after
* cpu_wait_death() timed out and reported the error. The
* caller is free to proceed, in which case the state
* will be reset properly by cpu_set_state_online().
* Proceeding despite this -EBUSY return makes sense
* for systems where the outgoing CPUs take themselves
* offline, with no post-death manipulation required from
* a surviving CPU.
*/
return -EBUSY;
case CPU_BROKEN:
/*
* The most likely reason we got here is that there was
* a timeout during CPU death, and the outgoing CPU never
* did complete its processing. This could happen on
* a virtualized system if the outgoing VCPU gets preempted
* for more than five seconds, and the user attempts to
* immediately online that same CPU. Trying again later
* might return -EBUSY above, hence -EAGAIN.
*/
return -EAGAIN;
default:
/* Should not happen. Famous last words. */
return -EIO;
}
}
/*
* Mark the specified CPU online.
*
* Note that it is permissible to omit this call entirely, as is
* done in architectures that do no CPU-hotplug error checking.
*/
void cpu_set_state_online(int cpu)
{
(void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Wait for the specified CPU to exit the idle loop and die.
*/
bool cpu_wait_death(unsigned int cpu, int seconds)
{
int jf_left = seconds * HZ;
int oldstate;
bool ret = true;
int sleep_jf = 1;
might_sleep();
/* The outgoing CPU will normally get done quite quickly. */
if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
goto update_state;
udelay(5);
/* But if the outgoing CPU dawdles, wait increasingly long times. */
while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
schedule_timeout_uninterruptible(sleep_jf);
jf_left -= sleep_jf;
if (jf_left <= 0)
break;
sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
}
update_state:
oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
if (oldstate == CPU_DEAD) {
/* Outgoing CPU died normally, update state. */
smp_mb(); /* atomic_read() before update. */
atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
} else {
/* Outgoing CPU still hasn't died, set state accordingly. */
if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
oldstate, CPU_BROKEN) != oldstate)
goto update_state;
ret = false;
}
return ret;
}
/*
* Called by the outgoing CPU to report its successful death. Return
* false if this report follows the surviving CPU's timing out.
*
* A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
* timed out. This approach allows architectures to omit calls to
* cpu_check_up_prepare() and cpu_set_state_online() without defeating
* the next cpu_wait_death()'s polling loop.
*/
bool cpu_report_death(void)
{
int oldstate;
int newstate;
int cpu = smp_processor_id();
do {
oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
if (oldstate != CPU_BROKEN)
newstate = CPU_DEAD;
else
newstate = CPU_DEAD_FROZEN;
} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
oldstate, newstate) != oldstate);
return newstate == CPU_DEAD;
}
#endif /* #ifdef CONFIG_HOTPLUG_CPU */

35
lib/Kconfig.debug
View File

@ -1180,16 +1180,7 @@ config DEBUG_CREDENTIALS
menu "RCU Debugging"
config PROVE_RCU
bool "RCU debugging: prove RCU correctness"
depends on PROVE_LOCKING
default n
help
This feature enables lockdep extensions that check for correct
use of RCU APIs. This is currently under development. Say Y
if you want to debug RCU usage or help work on the PROVE_RCU
feature.
Say N if you are unsure.
def_bool PROVE_LOCKING
config PROVE_RCU_REPEATEDLY
bool "RCU debugging: don't disable PROVE_RCU on first splat"
@ -1257,6 +1248,30 @@ config RCU_TORTURE_TEST_RUNNABLE
Say N here if you want the RCU torture tests to start only
after being manually enabled via /proc.
config RCU_TORTURE_TEST_SLOW_INIT
bool "Slow down RCU grace-period initialization to expose races"
depends on RCU_TORTURE_TEST
help
This option makes grace-period initialization block for a
few jiffies between initializing each pair of consecutive
rcu_node structures. This helps to expose races involving
grace-period initialization, in other words, it makes your
kernel less stable. It can also greatly increase grace-period
latency, especially on systems with large numbers of CPUs.
This is useful when torture-testing RCU, but in almost no
other circumstance.
Say Y here if you want your system to crash and hang more often.
Say N if you want a sane system.
config RCU_TORTURE_TEST_SLOW_INIT_DELAY
int "How much to slow down RCU grace-period initialization"
range 0 5
default 3
help
This option specifies the number of jiffies to wait between
each rcu_node structure initialization.
config RCU_CPU_STALL_TIMEOUT
int "RCU CPU stall timeout in seconds"
depends on RCU_STALL_COMMON

2
tools/testing/selftests/rcutorture/bin/kvm.sh
View File

@ -310,7 +310,7 @@ function dump(first, pastlast)
cfr[jn] = cf[j] "." cfrep[cf[j]];
}
if (cpusr[jn] > ncpus && ncpus != 0)
ovf = "(!)";
ovf = "-ovf";
else
ovf = "";
print "echo ", cfr[jn], cpusr[jn] ovf ": Starting build. `date`";

1
tools/testing/selftests/rcutorture/configs/rcu/CFcommon
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@ -1,2 +1,3 @@
CONFIG_RCU_TORTURE_TEST=y
CONFIG_PRINTK_TIME=y
CONFIG_RCU_TORTURE_TEST_SLOW_INIT=y