![Paul E. McKenney](/assets/img/avatar_default.png)
Peter Zijlstra proposed using SRCU to reduce mmap_sem contention [1,2], however, there are workloads that could result in a high volume of concurrent invocations of call_srcu(), which with current SRCU would result in excessive lock contention on the srcu_struct structure's ->queue_lock, which protects SRCU's callback lists. This commit therefore moves SRCU to per-CPU callback lists, thus greatly reducing contention. Because a given SRCU instance no longer has a single centralized callback list, starting grace periods and invoking callbacks are both more complex than in the single-list Classic SRCU implementation. Starting grace periods and handling callbacks are now handled using an srcu_node tree that is in some ways similar to the rcu_node trees used by RCU-bh, RCU-preempt, and RCU-sched (for example, the srcu_node tree shape is controlled by exactly the same Kconfig options and boot parameters that control the shape of the rcu_node tree). In addition, the old per-CPU srcu_array structure is now named srcu_data and contains an rcu_segcblist structure named ->srcu_cblist for its callbacks (and a spinlock to protect this). The srcu_struct gets an srcu_gp_seq that is used to associate callback segments with the corresponding completion-time grace-period number. These completion-time grace-period numbers are propagated up the srcu_node tree so that the grace-period workqueue handler can determine whether additional grace periods are needed on the one hand and where to look for callbacks that are ready to be invoked. The srcu_barrier() function must now wait on all instances of the per-CPU ->srcu_cblist. Because each ->srcu_cblist is protected by ->lock, srcu_barrier() can remotely add the needed callbacks. In theory, it could also remotely start grace periods, but in practice doing so is complex and racy. And interestingly enough, it is never necessary for srcu_barrier() to start a grace period because srcu_barrier() only enqueues a callback when a callback is already present--and it turns out that a grace period has to have already been started for this pre-existing callback. Furthermore, it is only the callback that srcu_barrier() needs to wait on, not any particular grace period. Therefore, a new rcu_segcblist_entrain() function enqueues the srcu_barrier() function's callback into the same segment occupied by the last pre-existing callback in the list. The special case where all the pre-existing callbacks are on a different list (because they are in the process of being invoked) is handled by enqueuing srcu_barrier()'s callback into the RCU_DONE_TAIL segment, relying on the done-callbacks check that takes place after all callbacks are inovked. Note that the readers use the same algorithm as before. Note that there is a separate srcu_idx that tells the readers what counter to increment. This unfortunately cannot be combined with srcu_gp_seq because they need to be incremented at different times. This commit introduces some ugly #ifdefs in rcutorture. These will go away when I feel good enough about Tree SRCU to ditch Classic SRCU. Some crude performance comparisons, courtesy of a quickly hacked rcuperf asynchronous-grace-period capability: Callback Queuing Overhead ------------------------- # CPUS Classic SRCU Tree SRCU ------ ------------ --------- 2 0.349 us 0.342 us 16 31.66 us 0.4 us 41 --------- 0.417 us The times are the 90th percentiles, a statistic that was chosen to reject the overheads of the occasional srcu_barrier() call needed to avoid OOMing the test machine. The rcuperf test hangs when running Classic SRCU at 41 CPUs, hence the line of dashes. Despite the hacks to both the rcuperf code and that statistics, this is a convincing demonstration of Tree SRCU's performance and scalability advantages. [1] https://lwn.net/Articles/309030/ [2] https://patchwork.kernel.org/patch/5108281/ Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Fix initialization if synchronize_srcu_expedited() called first. ]
625 lines
24 KiB
C
625 lines
24 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, you can access it online at
|
|
* http://www.gnu.org/licenses/gpl-2.0.html.
|
|
*
|
|
* 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/rtmutex.h>
|
|
#include <linux/threads.h>
|
|
#include <linux/cpumask.h>
|
|
#include <linux/seqlock.h>
|
|
#include <linux/swait.h>
|
|
#include <linux/stop_machine.h>
|
|
#include <linux/rcu_segcblist.h>
|
|
#include <linux/rcu_node_tree.h>
|
|
|
|
/*
|
|
* Dynticks per-CPU state.
|
|
*/
|
|
struct rcu_dynticks {
|
|
long long dynticks_nesting; /* Track irq/process nesting level. */
|
|
/* Process level is worth LLONG_MAX/2. */
|
|
int dynticks_nmi_nesting; /* Track NMI nesting level. */
|
|
atomic_t dynticks; /* Even value for idle, else odd. */
|
|
bool rcu_need_heavy_qs; /* GP old, need heavy quiescent state. */
|
|
unsigned long rcu_qs_ctr; /* Light universal quiescent state ctr. */
|
|
bool rcu_urgent_qs; /* GP old need light quiescent state. */
|
|
#ifdef CONFIG_NO_HZ_FULL_SYSIDLE
|
|
long long dynticks_idle_nesting;
|
|
/* irq/process nesting level from idle. */
|
|
atomic_t dynticks_idle; /* Even value for idle, else odd. */
|
|
/* "Idle" excludes userspace execution. */
|
|
unsigned long dynticks_idle_jiffies;
|
|
/* End of last non-NMI non-idle period. */
|
|
#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
|
|
#ifdef CONFIG_RCU_FAST_NO_HZ
|
|
bool all_lazy; /* Are all CPU's CBs lazy? */
|
|
unsigned long nonlazy_posted;
|
|
/* # times non-lazy CBs posted to CPU. */
|
|
unsigned long nonlazy_posted_snap;
|
|
/* idle-period nonlazy_posted snapshot. */
|
|
unsigned long last_accelerate;
|
|
/* Last jiffy CBs were accelerated. */
|
|
unsigned long last_advance_all;
|
|
/* Last jiffy CBs were all advanced. */
|
|
int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
|
|
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
|
|
};
|
|
|
|
/* RCU's kthread states for tracing. */
|
|
#define RCU_KTHREAD_STOPPED 0
|
|
#define RCU_KTHREAD_RUNNING 1
|
|
#define RCU_KTHREAD_WAITING 2
|
|
#define RCU_KTHREAD_OFFCPU 3
|
|
#define RCU_KTHREAD_YIELDING 4
|
|
#define RCU_KTHREAD_MAX 4
|
|
|
|
/*
|
|
* Definition for node within the RCU grace-period-detection hierarchy.
|
|
*/
|
|
struct rcu_node {
|
|
raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
|
|
/* some rcu_state fields as well as */
|
|
/* following. */
|
|
unsigned long gpnum; /* Current grace period for this node. */
|
|
/* This will either be equal to or one */
|
|
/* behind the root rcu_node's gpnum. */
|
|
unsigned long completed; /* Last GP 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 qsmaskinit;
|
|
/* Per-GP initial value for qsmask. */
|
|
/* Initialized from ->qsmaskinitnext at the */
|
|
/* beginning of each grace period. */
|
|
unsigned long qsmaskinitnext;
|
|
/* Online CPUs for next grace period. */
|
|
unsigned long expmask; /* CPUs or groups that need to check in */
|
|
/* to allow the current expedited GP */
|
|
/* to complete. */
|
|
unsigned long expmaskinit;
|
|
/* Per-GP initial values for expmask. */
|
|
/* Initialized from ->expmaskinitnext at the */
|
|
/* beginning of each expedited GP. */
|
|
unsigned long expmaskinitnext;
|
|
/* Online CPUs for next expedited GP. */
|
|
/* Any CPU that has ever been online will */
|
|
/* have its bit set. */
|
|
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 */
|
|
/* section. Tasks are placed at the head */
|
|
/* of this list and age towards the tail. */
|
|
struct list_head *gp_tasks;
|
|
/* Pointer to the first task blocking the */
|
|
/* current grace period, or NULL if there */
|
|
/* is no such task. */
|
|
struct list_head *exp_tasks;
|
|
/* Pointer to the first task blocking the */
|
|
/* current expedited grace period, or NULL */
|
|
/* if there is no such task. If there */
|
|
/* is no current expedited grace period, */
|
|
/* then there can cannot be any such task. */
|
|
struct list_head *boost_tasks;
|
|
/* Pointer to first task that needs to be */
|
|
/* priority boosted, or NULL if no priority */
|
|
/* boosting is needed for this rcu_node */
|
|
/* structure. If there are no tasks */
|
|
/* queued on this rcu_node structure that */
|
|
/* are blocking the current grace period, */
|
|
/* there can be no such task. */
|
|
struct rt_mutex boost_mtx;
|
|
/* Used only for the priority-boosting */
|
|
/* side effect, not as a lock. */
|
|
unsigned long boost_time;
|
|
/* When to start boosting (jiffies). */
|
|
struct task_struct *boost_kthread_task;
|
|
/* kthread that takes care of priority */
|
|
/* boosting for this rcu_node structure. */
|
|
unsigned int boost_kthread_status;
|
|
/* State of boost_kthread_task for tracing. */
|
|
unsigned long n_tasks_boosted;
|
|
/* Total number of tasks boosted. */
|
|
unsigned long n_exp_boosts;
|
|
/* Number of tasks boosted for expedited GP. */
|
|
unsigned long n_normal_boosts;
|
|
/* Number of tasks boosted for normal GP. */
|
|
unsigned long n_balk_blkd_tasks;
|
|
/* Refused to boost: no blocked tasks. */
|
|
unsigned long n_balk_exp_gp_tasks;
|
|
/* Refused to boost: nothing blocking GP. */
|
|
unsigned long n_balk_boost_tasks;
|
|
/* Refused to boost: already boosting. */
|
|
unsigned long n_balk_notblocked;
|
|
/* Refused to boost: RCU RS CS still running. */
|
|
unsigned long n_balk_notyet;
|
|
/* Refused to boost: not yet time. */
|
|
unsigned long n_balk_nos;
|
|
/* Refused to boost: not sure why, though. */
|
|
/* This can happen due to race conditions. */
|
|
#ifdef CONFIG_RCU_NOCB_CPU
|
|
struct swait_queue_head nocb_gp_wq[2];
|
|
/* Place for rcu_nocb_kthread() to wait GP. */
|
|
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
|
|
int need_future_gp[2];
|
|
/* Counts of upcoming no-CB GP requests. */
|
|
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
|
|
|
|
spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
|
|
unsigned long exp_seq_rq;
|
|
wait_queue_head_t exp_wq[4];
|
|
} ____cacheline_internodealigned_in_smp;
|
|
|
|
/*
|
|
* Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and
|
|
* are indexed relative to this interval rather than the global CPU ID space.
|
|
* This generates the bit for a CPU in node-local masks.
|
|
*/
|
|
#define leaf_node_cpu_bit(rnp, cpu) (1UL << ((cpu) - (rnp)->grplo))
|
|
|
|
/*
|
|
* Union to allow "aggregate OR" operation on the need for a quiescent
|
|
* state by the normal and expedited grace periods.
|
|
*/
|
|
union rcu_noqs {
|
|
struct {
|
|
u8 norm;
|
|
u8 exp;
|
|
} b; /* Bits. */
|
|
u16 s; /* Set of bits, aggregate OR here. */
|
|
};
|
|
|
|
/* 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 : */
|
|
unsigned long completed; /* Track rsp->completed gp number */
|
|
/* in order to detect GP end. */
|
|
unsigned long gpnum; /* Highest gp number that this CPU */
|
|
/* is aware of having started. */
|
|
unsigned long rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
|
|
/* for rcu_all_qs() invocations. */
|
|
union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
|
|
bool core_needs_qs; /* Core waits for quiesc state. */
|
|
bool beenonline; /* CPU online at least once. */
|
|
bool gpwrap; /* Possible gpnum/completed wrap. */
|
|
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
|
|
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
|
|
unsigned long ticks_this_gp; /* The number of scheduling-clock */
|
|
/* ticks this CPU has handled */
|
|
/* during and after the last grace */
|
|
/* period it is aware of. */
|
|
|
|
/* 2) batch handling */
|
|
struct rcu_segcblist cblist; /* Segmented callback list, with */
|
|
/* different callbacks waiting for */
|
|
/* different grace periods. */
|
|
long qlen_last_fqs_check;
|
|
/* qlen at last check for QS forcing */
|
|
unsigned long n_cbs_invoked; /* count of RCU cbs invoked. */
|
|
unsigned long n_nocbs_invoked; /* count of no-CBs RCU cbs invoked. */
|
|
unsigned long n_cbs_orphaned; /* RCU cbs orphaned by dying CPU */
|
|
unsigned long n_cbs_adopted; /* RCU cbs adopted from dying CPU */
|
|
unsigned long n_force_qs_snap;
|
|
/* did other CPU force QS recently? */
|
|
long blimit; /* Upper limit on a processed batch */
|
|
|
|
/* 3) dynticks interface. */
|
|
struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
|
|
int dynticks_snap; /* Per-GP tracking for dynticks. */
|
|
|
|
/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
|
|
unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
|
|
unsigned long offline_fqs; /* Kicked due to being offline. */
|
|
unsigned long cond_resched_completed;
|
|
/* Grace period that needs help */
|
|
/* from cond_resched(). */
|
|
|
|
/* 5) __rcu_pending() statistics. */
|
|
unsigned long n_rcu_pending; /* rcu_pending() calls since boot. */
|
|
unsigned long n_rp_core_needs_qs;
|
|
unsigned long n_rp_report_qs;
|
|
unsigned long n_rp_cb_ready;
|
|
unsigned long n_rp_cpu_needs_gp;
|
|
unsigned long n_rp_gp_completed;
|
|
unsigned long n_rp_gp_started;
|
|
unsigned long n_rp_nocb_defer_wakeup;
|
|
unsigned long n_rp_need_nothing;
|
|
|
|
/* 6) _rcu_barrier(), OOM callbacks, and expediting. */
|
|
struct rcu_head barrier_head;
|
|
#ifdef CONFIG_RCU_FAST_NO_HZ
|
|
struct rcu_head oom_head;
|
|
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
|
|
atomic_long_t exp_workdone0; /* # done by workqueue. */
|
|
atomic_long_t exp_workdone1; /* # done by others #1. */
|
|
atomic_long_t exp_workdone2; /* # done by others #2. */
|
|
atomic_long_t exp_workdone3; /* # done by others #3. */
|
|
int exp_dynticks_snap; /* Double-check need for IPI. */
|
|
|
|
/* 7) Callback offloading. */
|
|
#ifdef CONFIG_RCU_NOCB_CPU
|
|
struct rcu_head *nocb_head; /* CBs waiting for kthread. */
|
|
struct rcu_head **nocb_tail;
|
|
atomic_long_t nocb_q_count; /* # CBs waiting for nocb */
|
|
atomic_long_t nocb_q_count_lazy; /* invocation (all stages). */
|
|
struct rcu_head *nocb_follower_head; /* CBs ready to invoke. */
|
|
struct rcu_head **nocb_follower_tail;
|
|
struct swait_queue_head nocb_wq; /* For nocb kthreads to sleep on. */
|
|
struct task_struct *nocb_kthread;
|
|
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
|
|
|
|
/* The following fields are used by the leader, hence own cacheline. */
|
|
struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp;
|
|
/* CBs waiting for GP. */
|
|
struct rcu_head **nocb_gp_tail;
|
|
bool nocb_leader_sleep; /* Is the nocb leader thread asleep? */
|
|
struct rcu_data *nocb_next_follower;
|
|
/* Next follower in wakeup chain. */
|
|
|
|
/* The following fields are used by the follower, hence new cachline. */
|
|
struct rcu_data *nocb_leader ____cacheline_internodealigned_in_smp;
|
|
/* Leader CPU takes GP-end wakeups. */
|
|
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
|
|
|
|
/* 8) RCU CPU stall data. */
|
|
unsigned int softirq_snap; /* Snapshot of softirq activity. */
|
|
|
|
int cpu;
|
|
struct rcu_state *rsp;
|
|
};
|
|
|
|
/* Values for nocb_defer_wakeup field in struct rcu_data. */
|
|
#define RCU_NOGP_WAKE_NOT 0
|
|
#define RCU_NOGP_WAKE 1
|
|
#define RCU_NOGP_WAKE_FORCE 2
|
|
|
|
#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
|
|
/* For jiffies_till_first_fqs and */
|
|
/* and jiffies_till_next_fqs. */
|
|
|
|
#define RCU_JIFFIES_FQS_DIV 256 /* Very large systems need more */
|
|
/* delay between bouts of */
|
|
/* quiescent-state forcing. */
|
|
|
|
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time to take */
|
|
/* at least one scheduling clock */
|
|
/* irq before ratting on them. */
|
|
|
|
#define rcu_wait(cond) \
|
|
do { \
|
|
for (;;) { \
|
|
set_current_state(TASK_INTERRUPTIBLE); \
|
|
if (cond) \
|
|
break; \
|
|
schedule(); \
|
|
} \
|
|
__set_current_state(TASK_RUNNING); \
|
|
} while (0)
|
|
|
|
/*
|
|
* 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[RCU_NUM_LVLS + 1];
|
|
/* Hierarchy levels (+1 to */
|
|
/* shut bogus gcc warning) */
|
|
struct rcu_data __percpu *rda; /* pointer of percu rcu_data. */
|
|
call_rcu_func_t call; /* call_rcu() flavor. */
|
|
int ncpus; /* # CPUs seen so far. */
|
|
|
|
/* The following fields are guarded by the root rcu_node's lock. */
|
|
|
|
u8 boost ____cacheline_internodealigned_in_smp;
|
|
/* Subject to priority boost. */
|
|
unsigned long gpnum; /* Current gp number. */
|
|
unsigned long completed; /* # of last completed gp. */
|
|
struct task_struct *gp_kthread; /* Task for grace periods. */
|
|
struct swait_queue_head gp_wq; /* Where GP task waits. */
|
|
short gp_flags; /* Commands for GP task. */
|
|
short gp_state; /* GP kthread sleep state. */
|
|
|
|
/* End of fields guarded by root rcu_node's lock. */
|
|
|
|
raw_spinlock_t orphan_lock ____cacheline_internodealigned_in_smp;
|
|
/* Protect following fields. */
|
|
struct rcu_cblist orphan_pend; /* Orphaned callbacks that */
|
|
/* need a grace period. */
|
|
struct rcu_cblist orphan_done; /* Orphaned callbacks that */
|
|
/* are ready to invoke. */
|
|
/* (Contains counts.) */
|
|
/* End of fields guarded by orphan_lock. */
|
|
|
|
struct mutex barrier_mutex; /* Guards barrier fields. */
|
|
atomic_t barrier_cpu_count; /* # CPUs waiting on. */
|
|
struct completion barrier_completion; /* Wake at barrier end. */
|
|
unsigned long barrier_sequence; /* ++ at start and end of */
|
|
/* _rcu_barrier(). */
|
|
/* End of fields guarded by barrier_mutex. */
|
|
|
|
struct mutex exp_mutex; /* Serialize expedited GP. */
|
|
struct mutex exp_wake_mutex; /* Serialize wakeup. */
|
|
unsigned long expedited_sequence; /* Take a ticket. */
|
|
atomic_t expedited_need_qs; /* # CPUs left to check in. */
|
|
struct swait_queue_head expedited_wq; /* Wait for check-ins. */
|
|
int ncpus_snap; /* # CPUs seen last time. */
|
|
|
|
unsigned long jiffies_force_qs; /* Time at which to invoke */
|
|
/* force_quiescent_state(). */
|
|
unsigned long jiffies_kick_kthreads; /* Time at which to kick */
|
|
/* kthreads, if configured. */
|
|
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. */
|
|
unsigned long gp_start; /* Time at which GP started, */
|
|
/* but in jiffies. */
|
|
unsigned long gp_activity; /* Time of last GP kthread */
|
|
/* activity in jiffies. */
|
|
unsigned long jiffies_stall; /* Time at which to check */
|
|
/* for CPU stalls. */
|
|
unsigned long jiffies_resched; /* Time at which to resched */
|
|
/* a reluctant CPU. */
|
|
unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
|
|
/* GP start. */
|
|
unsigned long gp_max; /* Maximum GP duration in */
|
|
/* jiffies. */
|
|
const char *name; /* Name of structure. */
|
|
char abbr; /* Abbreviated name. */
|
|
struct list_head flavors; /* List of RCU flavors. */
|
|
};
|
|
|
|
/* Values for rcu_state structure's gp_flags field. */
|
|
#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
|
|
#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
|
|
|
|
/* Values for rcu_state structure's gp_state field. */
|
|
#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
|
|
#define RCU_GP_WAIT_GPS 1 /* Wait for grace-period start. */
|
|
#define RCU_GP_DONE_GPS 2 /* Wait done for grace-period start. */
|
|
#define RCU_GP_WAIT_FQS 3 /* Wait for force-quiescent-state time. */
|
|
#define RCU_GP_DOING_FQS 4 /* Wait done for force-quiescent-state time. */
|
|
#define RCU_GP_CLEANUP 5 /* Grace-period cleanup started. */
|
|
#define RCU_GP_CLEANED 6 /* Grace-period cleanup complete. */
|
|
|
|
#ifndef RCU_TREE_NONCORE
|
|
static const char * const gp_state_names[] = {
|
|
"RCU_GP_IDLE",
|
|
"RCU_GP_WAIT_GPS",
|
|
"RCU_GP_DONE_GPS",
|
|
"RCU_GP_WAIT_FQS",
|
|
"RCU_GP_DOING_FQS",
|
|
"RCU_GP_CLEANUP",
|
|
"RCU_GP_CLEANED",
|
|
};
|
|
#endif /* #ifndef RCU_TREE_NONCORE */
|
|
|
|
extern struct list_head rcu_struct_flavors;
|
|
|
|
/* Sequence through rcu_state structures for each RCU flavor. */
|
|
#define for_each_rcu_flavor(rsp) \
|
|
list_for_each_entry((rsp), &rcu_struct_flavors, flavors)
|
|
|
|
/*
|
|
* RCU implementation internal declarations:
|
|
*/
|
|
extern struct rcu_state rcu_sched_state;
|
|
|
|
extern struct rcu_state rcu_bh_state;
|
|
|
|
#ifdef CONFIG_PREEMPT_RCU
|
|
extern struct rcu_state rcu_preempt_state;
|
|
#endif /* #ifdef CONFIG_PREEMPT_RCU */
|
|
|
|
int rcu_dynticks_snap(struct rcu_dynticks *rdtp);
|
|
bool rcu_eqs_special_set(int cpu);
|
|
|
|
#ifdef CONFIG_RCU_BOOST
|
|
DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
|
|
DECLARE_PER_CPU(int, rcu_cpu_kthread_cpu);
|
|
DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
|
|
DECLARE_PER_CPU(char, rcu_cpu_has_work);
|
|
#endif /* #ifdef CONFIG_RCU_BOOST */
|
|
|
|
#ifndef RCU_TREE_NONCORE
|
|
|
|
/* Forward declarations for rcutree_plugin.h */
|
|
static void rcu_bootup_announce(void);
|
|
static void rcu_preempt_note_context_switch(void);
|
|
static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
|
|
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
|
|
static void rcu_print_detail_task_stall(struct rcu_state *rsp);
|
|
static int rcu_print_task_stall(struct rcu_node *rnp);
|
|
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
|
|
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
|
|
static void rcu_preempt_check_callbacks(void);
|
|
void call_rcu(struct rcu_head *head, rcu_callback_t func);
|
|
static void __init __rcu_init_preempt(void);
|
|
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
|
|
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
|
|
static void invoke_rcu_callbacks_kthread(void);
|
|
static bool rcu_is_callbacks_kthread(void);
|
|
#ifdef CONFIG_RCU_BOOST
|
|
static void rcu_preempt_do_callbacks(void);
|
|
static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
|
|
struct rcu_node *rnp);
|
|
#endif /* #ifdef CONFIG_RCU_BOOST */
|
|
static void __init rcu_spawn_boost_kthreads(void);
|
|
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);
|
|
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
|
|
static void increment_cpu_stall_ticks(void);
|
|
static bool rcu_nocb_cpu_needs_barrier(struct rcu_state *rsp, int cpu);
|
|
static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq);
|
|
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
|
|
static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
|
|
static void rcu_init_one_nocb(struct rcu_node *rnp);
|
|
static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
|
|
bool lazy, unsigned long flags);
|
|
static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp,
|
|
struct rcu_data *rdp,
|
|
unsigned long flags);
|
|
static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
|
|
static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
|
|
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
|
|
static void rcu_spawn_all_nocb_kthreads(int cpu);
|
|
static void __init rcu_spawn_nocb_kthreads(void);
|
|
#ifdef CONFIG_RCU_NOCB_CPU
|
|
static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
|
|
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
|
|
static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
|
|
static bool init_nocb_callback_list(struct rcu_data *rdp);
|
|
static void rcu_sysidle_enter(int irq);
|
|
static void rcu_sysidle_exit(int irq);
|
|
static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
|
|
unsigned long *maxj);
|
|
static bool is_sysidle_rcu_state(struct rcu_state *rsp);
|
|
static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle,
|
|
unsigned long maxj);
|
|
static void rcu_bind_gp_kthread(void);
|
|
static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp);
|
|
static bool rcu_nohz_full_cpu(struct rcu_state *rsp);
|
|
static void rcu_dynticks_task_enter(void);
|
|
static void rcu_dynticks_task_exit(void);
|
|
|
|
#ifdef CONFIG_SRCU
|
|
void srcu_online_cpu(unsigned int cpu);
|
|
void srcu_offline_cpu(unsigned int cpu);
|
|
#else /* #ifdef CONFIG_SRCU */
|
|
void srcu_online_cpu(unsigned int cpu) { }
|
|
void srcu_offline_cpu(unsigned int cpu) { }
|
|
#endif /* #else #ifdef CONFIG_SRCU */
|
|
|
|
#endif /* #ifndef RCU_TREE_NONCORE */
|
|
|
|
#ifdef CONFIG_RCU_TRACE
|
|
/* Read out queue lengths for tracing. */
|
|
static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll)
|
|
{
|
|
#ifdef CONFIG_RCU_NOCB_CPU
|
|
*ql = atomic_long_read(&rdp->nocb_q_count);
|
|
*qll = atomic_long_read(&rdp->nocb_q_count_lazy);
|
|
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
|
|
*ql = 0;
|
|
*qll = 0;
|
|
#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
|
|
}
|
|
#endif /* #ifdef CONFIG_RCU_TRACE */
|
|
|
|
/*
|
|
* Wrappers for the rcu_node::lock acquire and release.
|
|
*
|
|
* Because the rcu_nodes form a tree, the tree traversal locking will observe
|
|
* different lock values, this in turn means that an UNLOCK of one level
|
|
* followed by a LOCK of another level does not imply a full memory barrier;
|
|
* and most importantly transitivity is lost.
|
|
*
|
|
* In order to restore full ordering between tree levels, augment the regular
|
|
* lock acquire functions with smp_mb__after_unlock_lock().
|
|
*
|
|
* As ->lock of struct rcu_node is a __private field, therefore one should use
|
|
* these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock.
|
|
*/
|
|
static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp)
|
|
{
|
|
raw_spin_lock(&ACCESS_PRIVATE(rnp, lock));
|
|
smp_mb__after_unlock_lock();
|
|
}
|
|
|
|
static inline void raw_spin_unlock_rcu_node(struct rcu_node *rnp)
|
|
{
|
|
raw_spin_unlock(&ACCESS_PRIVATE(rnp, lock));
|
|
}
|
|
|
|
static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp)
|
|
{
|
|
raw_spin_lock_irq(&ACCESS_PRIVATE(rnp, lock));
|
|
smp_mb__after_unlock_lock();
|
|
}
|
|
|
|
static inline void raw_spin_unlock_irq_rcu_node(struct rcu_node *rnp)
|
|
{
|
|
raw_spin_unlock_irq(&ACCESS_PRIVATE(rnp, lock));
|
|
}
|
|
|
|
#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \
|
|
do { \
|
|
typecheck(unsigned long, flags); \
|
|
raw_spin_lock_irqsave(&ACCESS_PRIVATE(rnp, lock), flags); \
|
|
smp_mb__after_unlock_lock(); \
|
|
} while (0)
|
|
|
|
#define raw_spin_unlock_irqrestore_rcu_node(rnp, flags) \
|
|
do { \
|
|
typecheck(unsigned long, flags); \
|
|
raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(rnp, lock), flags); \
|
|
} while (0)
|
|
|
|
static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp)
|
|
{
|
|
bool locked = raw_spin_trylock(&ACCESS_PRIVATE(rnp, lock));
|
|
|
|
if (locked)
|
|
smp_mb__after_unlock_lock();
|
|
return locked;
|
|
}
|