mirror of
https://github.com/torvalds/linux.git
synced 2024-12-16 16:12:52 +00:00
d9a3da0699
Implement an synchronize_rcu_expedited() for preemptible RCU that actually is expedited. This uses synchronize_sched_expedited() to force all threads currently running in a preemptible-RCU read-side critical section onto the appropriate ->blocked_tasks[] list, then takes a snapshot of all of these lists and waits for them to drain. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1259784616158-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
372 lines
15 KiB
C
372 lines
15 KiB
C
/*
|
|
* Read-Copy Update mechanism for mutual exclusion (tree-based version)
|
|
* Internal non-public definitions.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
*
|
|
* Copyright IBM Corporation, 2008
|
|
*
|
|
* Author: Ingo Molnar <mingo@elte.hu>
|
|
* Paul E. McKenney <paulmck@linux.vnet.ibm.com>
|
|
*/
|
|
|
|
#include <linux/cache.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/threads.h>
|
|
#include <linux/cpumask.h>
|
|
#include <linux/seqlock.h>
|
|
|
|
/*
|
|
* Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
|
|
* In theory, it should be possible to add more levels straightforwardly.
|
|
* In practice, this has not been tested, so there is probably some
|
|
* bug somewhere.
|
|
*/
|
|
#define MAX_RCU_LVLS 4
|
|
#define RCU_FANOUT (CONFIG_RCU_FANOUT)
|
|
#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
|
|
#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
|
|
#define RCU_FANOUT_FOURTH (RCU_FANOUT_CUBE * RCU_FANOUT)
|
|
|
|
#if NR_CPUS <= RCU_FANOUT
|
|
# define NUM_RCU_LVLS 1
|
|
# define NUM_RCU_LVL_0 1
|
|
# define NUM_RCU_LVL_1 (NR_CPUS)
|
|
# define NUM_RCU_LVL_2 0
|
|
# define NUM_RCU_LVL_3 0
|
|
# define NUM_RCU_LVL_4 0
|
|
#elif NR_CPUS <= RCU_FANOUT_SQ
|
|
# define NUM_RCU_LVLS 2
|
|
# define NUM_RCU_LVL_0 1
|
|
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
|
|
# define NUM_RCU_LVL_2 (NR_CPUS)
|
|
# define NUM_RCU_LVL_3 0
|
|
# define NUM_RCU_LVL_4 0
|
|
#elif NR_CPUS <= RCU_FANOUT_CUBE
|
|
# define NUM_RCU_LVLS 3
|
|
# define NUM_RCU_LVL_0 1
|
|
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ)
|
|
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
|
|
# define NUM_RCU_LVL_3 NR_CPUS
|
|
# define NUM_RCU_LVL_4 0
|
|
#elif NR_CPUS <= RCU_FANOUT_FOURTH
|
|
# define NUM_RCU_LVLS 4
|
|
# define NUM_RCU_LVL_0 1
|
|
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_CUBE)
|
|
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_SQ)
|
|
# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT)
|
|
# define NUM_RCU_LVL_4 NR_CPUS
|
|
#else
|
|
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
|
|
#endif /* #if (NR_CPUS) <= RCU_FANOUT */
|
|
|
|
#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3 + NUM_RCU_LVL_4)
|
|
#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
|
|
|
|
/*
|
|
* Dynticks per-CPU state.
|
|
*/
|
|
struct rcu_dynticks {
|
|
int dynticks_nesting; /* Track nesting level, sort of. */
|
|
int dynticks; /* Even value for dynticks-idle, else odd. */
|
|
int dynticks_nmi; /* Even value for either dynticks-idle or */
|
|
/* not in nmi handler, else odd. So this */
|
|
/* remains even for nmi from irq handler. */
|
|
};
|
|
|
|
/*
|
|
* Definition for node within the RCU grace-period-detection hierarchy.
|
|
*/
|
|
struct rcu_node {
|
|
spinlock_t lock; /* Root rcu_node's lock protects some */
|
|
/* rcu_state fields as well as following. */
|
|
long gpnum; /* Current grace period for this node. */
|
|
/* This will either be equal to or one */
|
|
/* behind the root rcu_node's gpnum. */
|
|
long completed; /* Last grace period completed for this node. */
|
|
/* This will either be equal to or one */
|
|
/* behind the root rcu_node's gpnum. */
|
|
unsigned long qsmask; /* CPUs or groups that need to switch in */
|
|
/* order for current grace period to proceed.*/
|
|
/* In leaf rcu_node, each bit corresponds to */
|
|
/* an rcu_data structure, otherwise, each */
|
|
/* bit corresponds to a child rcu_node */
|
|
/* structure. */
|
|
unsigned long expmask; /* Groups that have ->blocked_tasks[] */
|
|
/* elements that need to drain to allow the */
|
|
/* current expedited grace period to */
|
|
/* complete (only for TREE_PREEMPT_RCU). */
|
|
unsigned long qsmaskinit;
|
|
/* Per-GP initial value for qsmask & expmask. */
|
|
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. */
|
|
struct rcu_node *parent;
|
|
struct list_head blocked_tasks[4];
|
|
/* Tasks blocked in RCU read-side critsect. */
|
|
/* Grace period number (->gpnum) x blocked */
|
|
/* by tasks on the (x & 0x1) element of the */
|
|
/* blocked_tasks[] array. */
|
|
} ____cacheline_internodealigned_in_smp;
|
|
|
|
/*
|
|
* Do a full breadth-first scan of the rcu_node structures for the
|
|
* specified rcu_state structure.
|
|
*/
|
|
#define rcu_for_each_node_breadth_first(rsp, rnp) \
|
|
for ((rnp) = &(rsp)->node[0]; \
|
|
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
|
|
|
|
/*
|
|
* Do a breadth-first scan of the non-leaf rcu_node structures for the
|
|
* specified rcu_state structure. Note that if there is a singleton
|
|
* rcu_node tree with but one rcu_node structure, this loop is a no-op.
|
|
*/
|
|
#define rcu_for_each_nonleaf_node_breadth_first(rsp, rnp) \
|
|
for ((rnp) = &(rsp)->node[0]; \
|
|
(rnp) < (rsp)->level[NUM_RCU_LVLS - 1]; (rnp)++)
|
|
|
|
/*
|
|
* Scan the leaves of the rcu_node hierarchy for the specified rcu_state
|
|
* structure. Note that if there is a singleton rcu_node tree with but
|
|
* one rcu_node structure, this loop -will- visit the rcu_node structure.
|
|
* It is still a leaf node, even if it is also the root node.
|
|
*/
|
|
#define rcu_for_each_leaf_node(rsp, rnp) \
|
|
for ((rnp) = (rsp)->level[NUM_RCU_LVLS - 1]; \
|
|
(rnp) < &(rsp)->node[NUM_RCU_NODES]; (rnp)++)
|
|
|
|
/* Index values for nxttail array in struct rcu_data. */
|
|
#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
|
|
#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
|
|
#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
|
|
#define RCU_NEXT_TAIL 3
|
|
#define RCU_NEXT_SIZE 4
|
|
|
|
/* Per-CPU data for read-copy update. */
|
|
struct rcu_data {
|
|
/* 1) quiescent-state and grace-period handling : */
|
|
long completed; /* Track rsp->completed gp number */
|
|
/* in order to detect GP end. */
|
|
long gpnum; /* Highest gp number that this CPU */
|
|
/* is aware of having started. */
|
|
long passed_quiesc_completed;
|
|
/* Value of completed at time of qs. */
|
|
bool passed_quiesc; /* User-mode/idle loop etc. */
|
|
bool qs_pending; /* Core waits for quiesc state. */
|
|
bool beenonline; /* CPU online at least once. */
|
|
bool preemptable; /* Preemptable RCU? */
|
|
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
|
|
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
|
|
|
|
/* 2) batch handling */
|
|
/*
|
|
* If nxtlist is not NULL, it is partitioned as follows.
|
|
* Any of the partitions might be empty, in which case the
|
|
* pointer to that partition will be equal to the pointer for
|
|
* the following partition. When the list is empty, all of
|
|
* the nxttail elements point to the ->nxtlist pointer itself,
|
|
* which in that case is NULL.
|
|
*
|
|
* [nxtlist, *nxttail[RCU_DONE_TAIL]):
|
|
* Entries that batch # <= ->completed
|
|
* The grace period for these entries has completed, and
|
|
* the other grace-period-completed entries may be moved
|
|
* here temporarily in rcu_process_callbacks().
|
|
* [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
|
|
* Entries that batch # <= ->completed - 1: waiting for current GP
|
|
* [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
|
|
* Entries known to have arrived before current GP ended
|
|
* [*nxttail[RCU_NEXT_READY_TAIL], *nxttail[RCU_NEXT_TAIL]):
|
|
* Entries that might have arrived after current GP ended
|
|
* Note that the value of *nxttail[RCU_NEXT_TAIL] will
|
|
* always be NULL, as this is the end of the list.
|
|
*/
|
|
struct rcu_head *nxtlist;
|
|
struct rcu_head **nxttail[RCU_NEXT_SIZE];
|
|
long qlen; /* # of queued callbacks */
|
|
long qlen_last_fqs_check;
|
|
/* qlen at last check for QS forcing */
|
|
unsigned long n_force_qs_snap;
|
|
/* did other CPU force QS recently? */
|
|
long blimit; /* Upper limit on a processed batch */
|
|
|
|
#ifdef CONFIG_NO_HZ
|
|
/* 3) dynticks interface. */
|
|
struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
|
|
int dynticks_snap; /* Per-GP tracking for dynticks. */
|
|
int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */
|
|
#endif /* #ifdef CONFIG_NO_HZ */
|
|
|
|
/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
|
|
#ifdef CONFIG_NO_HZ
|
|
unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
|
|
#endif /* #ifdef CONFIG_NO_HZ */
|
|
unsigned long offline_fqs; /* Kicked due to being offline. */
|
|
unsigned long resched_ipi; /* Sent a resched IPI. */
|
|
|
|
/* 5) __rcu_pending() statistics. */
|
|
long n_rcu_pending; /* rcu_pending() calls since boot. */
|
|
long n_rp_qs_pending;
|
|
long n_rp_cb_ready;
|
|
long n_rp_cpu_needs_gp;
|
|
long n_rp_gp_completed;
|
|
long n_rp_gp_started;
|
|
long n_rp_need_fqs;
|
|
long n_rp_need_nothing;
|
|
|
|
int cpu;
|
|
};
|
|
|
|
/* Values for signaled field in struct rcu_state. */
|
|
#define RCU_GP_IDLE 0 /* No grace period in progress. */
|
|
#define RCU_GP_INIT 1 /* Grace period being initialized. */
|
|
#define RCU_SAVE_DYNTICK 2 /* Need to scan dyntick state. */
|
|
#define RCU_SAVE_COMPLETED 3 /* Need to save rsp->completed. */
|
|
#define RCU_FORCE_QS 4 /* Need to force quiescent state. */
|
|
#ifdef CONFIG_NO_HZ
|
|
#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
|
|
#else /* #ifdef CONFIG_NO_HZ */
|
|
#define RCU_SIGNAL_INIT RCU_SAVE_COMPLETED
|
|
#endif /* #else #ifdef CONFIG_NO_HZ */
|
|
|
|
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
|
|
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
|
|
#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */
|
|
#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */
|
|
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
|
|
/* to take at least one */
|
|
/* scheduling clock irq */
|
|
/* before ratting on them. */
|
|
|
|
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
|
|
/*
|
|
* RCU global state, including node hierarchy. This hierarchy is
|
|
* represented in "heap" form in a dense array. The root (first level)
|
|
* of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
|
|
* level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
|
|
* and the third level in ->node[m+1] and following (->node[m+1] referenced
|
|
* by ->level[2]). The number of levels is determined by the number of
|
|
* CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
|
|
* consisting of a single rcu_node.
|
|
*/
|
|
struct rcu_state {
|
|
struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
|
|
struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
|
|
u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
|
|
u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
|
|
struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
|
|
|
|
/* The following fields are guarded by the root rcu_node's lock. */
|
|
|
|
u8 signaled ____cacheline_internodealigned_in_smp;
|
|
/* Force QS state. */
|
|
long gpnum; /* Current gp number. */
|
|
long completed; /* # of last completed gp. */
|
|
|
|
/* End of fields guarded by root rcu_node's lock. */
|
|
|
|
spinlock_t onofflock; /* exclude on/offline and */
|
|
/* starting new GP. Also */
|
|
/* protects the following */
|
|
/* orphan_cbs fields. */
|
|
struct rcu_head *orphan_cbs_list; /* list of rcu_head structs */
|
|
/* orphaned by all CPUs in */
|
|
/* a given leaf rcu_node */
|
|
/* going offline. */
|
|
struct rcu_head **orphan_cbs_tail; /* And tail pointer. */
|
|
long orphan_qlen; /* Number of orphaned cbs. */
|
|
spinlock_t fqslock; /* Only one task forcing */
|
|
/* quiescent states. */
|
|
long completed_fqs; /* Value of completed @ snap. */
|
|
/* Protected by fqslock. */
|
|
unsigned long jiffies_force_qs; /* Time at which to invoke */
|
|
/* force_quiescent_state(). */
|
|
unsigned long n_force_qs; /* Number of calls to */
|
|
/* force_quiescent_state(). */
|
|
unsigned long n_force_qs_lh; /* ~Number of calls leaving */
|
|
/* due to lock unavailable. */
|
|
unsigned long n_force_qs_ngp; /* Number of calls leaving */
|
|
/* due to no GP active. */
|
|
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
|
|
unsigned long gp_start; /* Time at which GP started, */
|
|
/* but in jiffies. */
|
|
unsigned long jiffies_stall; /* Time at which to check */
|
|
/* for CPU stalls. */
|
|
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
};
|
|
|
|
/* Return values for rcu_preempt_offline_tasks(). */
|
|
|
|
#define RCU_OFL_TASKS_NORM_GP 0x1 /* Tasks blocking normal */
|
|
/* GP were moved to root. */
|
|
#define RCU_OFL_TASKS_EXP_GP 0x2 /* Tasks blocking expedited */
|
|
/* GP were moved to root. */
|
|
|
|
#ifdef RCU_TREE_NONCORE
|
|
|
|
/*
|
|
* RCU implementation internal declarations:
|
|
*/
|
|
extern struct rcu_state rcu_sched_state;
|
|
DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
|
|
|
|
extern struct rcu_state rcu_bh_state;
|
|
DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
|
|
|
|
#ifdef CONFIG_TREE_PREEMPT_RCU
|
|
extern struct rcu_state rcu_preempt_state;
|
|
DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
|
|
#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
|
|
|
|
#else /* #ifdef RCU_TREE_NONCORE */
|
|
|
|
/* Forward declarations for rcutree_plugin.h */
|
|
static void rcu_bootup_announce(void);
|
|
long rcu_batches_completed(void);
|
|
static void rcu_preempt_note_context_switch(int cpu);
|
|
static int rcu_preempted_readers(struct rcu_node *rnp);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
|
|
unsigned long flags);
|
|
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
|
|
static void rcu_print_task_stall(struct rcu_node *rnp);
|
|
#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
|
|
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
|
|
struct rcu_node *rnp,
|
|
struct rcu_data *rdp);
|
|
static void rcu_preempt_offline_cpu(int cpu);
|
|
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
static void rcu_preempt_check_callbacks(int cpu);
|
|
static void rcu_preempt_process_callbacks(void);
|
|
void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
|
|
#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
|
|
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp);
|
|
#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
|
|
static int rcu_preempt_pending(int cpu);
|
|
static int rcu_preempt_needs_cpu(int cpu);
|
|
static void __cpuinit rcu_preempt_init_percpu_data(int cpu);
|
|
static void rcu_preempt_send_cbs_to_orphanage(void);
|
|
static void __init __rcu_init_preempt(void);
|
|
|
|
#endif /* #else #ifdef RCU_TREE_NONCORE */
|