diff options
31 files changed, 631 insertions, 629 deletions
diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index a27fbfb0efb8..65eb856526b7 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -1,3 +1,5 @@ +What is RCU? -- "Read, Copy, Update" + Please note that the "What is RCU?" LWN series is an excellent place to start learning about RCU: diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c index 7468de429087..3ea0047beb40 100644 --- a/arch/x86/kernel/cpu/mtrr/main.c +++ b/arch/x86/kernel/cpu/mtrr/main.c @@ -46,6 +46,7 @@ #include <linux/pci.h> #include <linux/smp.h> #include <linux/syscore_ops.h> +#include <linux/rcupdate.h> #include <asm/cpufeature.h> #include <asm/e820/api.h> @@ -793,6 +794,9 @@ void mtrr_ap_init(void) if (!use_intel() || mtrr_aps_delayed_init) return; + + rcu_cpu_starting(smp_processor_id()); + /* * Ideally we should hold mtrr_mutex here to avoid mtrr entries * changed, but this routine will be called in cpu boot time, diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 04a20da76786..c8b30067b6ae 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -357,7 +357,7 @@ static void nvme_free_ns_head(struct kref *ref) nvme_mpath_remove_disk(head); ida_simple_remove(&head->subsys->ns_ida, head->instance); list_del_init(&head->entry); - cleanup_srcu_struct(&head->srcu); + cleanup_srcu_struct_quiesced(&head->srcu); nvme_put_subsystem(head->subsys); kfree(head); } diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 36360d07f25b..e679b175b411 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -108,7 +108,6 @@ void rcu_sched_qs(void); void rcu_bh_qs(void); void rcu_check_callbacks(int user); void rcu_report_dead(unsigned int cpu); -void rcu_cpu_starting(unsigned int cpu); void rcutree_migrate_callbacks(int cpu); #ifdef CONFIG_RCU_STALL_COMMON @@ -188,13 +187,13 @@ static inline void exit_tasks_rcu_finish(void) { } #endif /* #else #ifdef CONFIG_TASKS_RCU */ /** - * cond_resched_rcu_qs - Report potential quiescent states to RCU + * cond_resched_tasks_rcu_qs - Report potential quiescent states to RCU * * This macro resembles cond_resched(), except that it is defined to * report potential quiescent states to RCU-tasks even if the cond_resched() * machinery were to be shut off, as some advocate for PREEMPT kernels. */ -#define cond_resched_rcu_qs() \ +#define cond_resched_tasks_rcu_qs() \ do { \ if (!cond_resched()) \ rcu_note_voluntary_context_switch_lite(current); \ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index ce9beec35e34..7b3c82e8a625 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -132,5 +132,6 @@ static inline void rcu_all_qs(void) { barrier(); } #define rcutree_offline_cpu NULL #define rcutree_dead_cpu NULL #define rcutree_dying_cpu NULL +static inline void rcu_cpu_starting(unsigned int cpu) { } #endif /* __LINUX_RCUTINY_H */ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index fd996cdf1833..914655848ef6 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -74,6 +74,7 @@ static inline void synchronize_rcu_bh_expedited(void) void rcu_barrier(void); void rcu_barrier_bh(void); void rcu_barrier_sched(void); +bool rcu_eqs_special_set(int cpu); unsigned long get_state_synchronize_rcu(void); void cond_synchronize_rcu(unsigned long oldstate); unsigned long get_state_synchronize_sched(void); @@ -100,5 +101,6 @@ int rcutree_online_cpu(unsigned int cpu); int rcutree_offline_cpu(unsigned int cpu); int rcutree_dead_cpu(unsigned int cpu); int rcutree_dying_cpu(unsigned int cpu); +void rcu_cpu_starting(unsigned int cpu); #endif /* __LINUX_RCUTREE_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index ca3f3eae8980..5a0c10b45273 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1661,7 +1661,6 @@ static inline int test_tsk_need_resched(struct task_struct *tsk) * explicit rescheduling in places that are safe. The return * value indicates whether a reschedule was done in fact. * cond_resched_lock() will drop the spinlock before scheduling, - * cond_resched_softirq() will enable bhs before scheduling. */ #ifndef CONFIG_PREEMPT extern int _cond_resched(void); @@ -1681,13 +1680,6 @@ extern int __cond_resched_lock(spinlock_t *lock); __cond_resched_lock(lock); \ }) -extern int __cond_resched_softirq(void); - -#define cond_resched_softirq() ({ \ - ___might_sleep(__FILE__, __LINE__, SOFTIRQ_DISABLE_OFFSET); \ - __cond_resched_softirq(); \ -}) - static inline void cond_resched_rcu(void) { #if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 33c1c698df09..91494d7e8e41 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -69,11 +69,45 @@ struct srcu_struct { }; void call_srcu(struct srcu_struct *sp, struct rcu_head *head, void (*func)(struct rcu_head *head)); -void cleanup_srcu_struct(struct srcu_struct *sp); +void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced); int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp); void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp); void synchronize_srcu(struct srcu_struct *sp); +/** + * cleanup_srcu_struct - deconstruct a sleep-RCU structure + * @sp: structure to clean up. + * + * Must invoke this after you are finished using a given srcu_struct that + * was initialized via init_srcu_struct(), else you leak memory. + */ +static inline void cleanup_srcu_struct(struct srcu_struct *sp) +{ + _cleanup_srcu_struct(sp, false); +} + +/** + * cleanup_srcu_struct_quiesced - deconstruct a quiesced sleep-RCU structure + * @sp: structure to clean up. + * + * Must invoke this after you are finished using a given srcu_struct that + * was initialized via init_srcu_struct(), else you leak memory. Also, + * all grace-period processing must have completed. + * + * "Completed" means that the last synchronize_srcu() and + * synchronize_srcu_expedited() calls must have returned before the call + * to cleanup_srcu_struct_quiesced(). It also means that the callback + * from the last call_srcu() must have been invoked before the call to + * cleanup_srcu_struct_quiesced(), but you can use srcu_barrier() to help + * with this last. Violating these rules will get you a WARN_ON() splat + * (with high probability, anyway), and will also cause the srcu_struct + * to be leaked. + */ +static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *sp) +{ + _cleanup_srcu_struct(sp, true); +} + #ifdef CONFIG_DEBUG_LOCK_ALLOC /** diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index d8c33298c153..5936aac357ab 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -84,20 +84,21 @@ TRACE_EVENT(rcu_grace_period, ); /* - * Tracepoint for future grace-period events, including those for no-callbacks - * CPUs. The caller should pull the data from the rcu_node structure, - * other than rcuname, which comes from the rcu_state structure, and event, - * which is one of the following: + * Tracepoint for future grace-period events. The caller should pull + * the data from the rcu_node structure, other than rcuname, which comes + * from the rcu_state structure, and event, which is one of the following: * - * "Startleaf": Request a nocb grace period based on leaf-node data. + * "Startleaf": Request a grace period based on leaf-node data. + * "Prestarted": Someone beat us to the request * "Startedleaf": Leaf-node start proved sufficient. * "Startedleafroot": Leaf-node start proved sufficient after checking root. * "Startedroot": Requested a nocb grace period based on root-node data. + * "NoGPkthread": The RCU grace-period kthread has not yet started. * "StartWait": Start waiting for the requested grace period. * "ResumeWait": Resume waiting after signal. * "EndWait": Complete wait. * "Cleanup": Clean up rcu_node structure after previous GP. - * "CleanupMore": Clean up, and another no-CB GP is needed. + * "CleanupMore": Clean up, and another GP is needed. */ TRACE_EVENT(rcu_future_grace_period, diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 7a693e31184a..40cea6735c2d 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -270,6 +270,12 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) } } +/* Returns first leaf rcu_node of the specified RCU flavor. */ +#define rcu_first_leaf_node(rsp) ((rsp)->level[rcu_num_lvls - 1]) + +/* Is this rcu_node a leaf? */ +#define rcu_is_leaf_node(rnp) ((rnp)->level == rcu_num_lvls - 1) + /* * Do a full breadth-first scan of the rcu_node structures for the * specified rcu_state structure. @@ -284,8 +290,7 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) * 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[rcu_num_lvls - 1]; (rnp)++) + for ((rnp) = &(rsp)->node[0]; !rcu_is_leaf_node(rsp, rnp); (rnp)++) /* * Scan the leaves of the rcu_node hierarchy for the specified rcu_state @@ -294,7 +299,7 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) * 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[rcu_num_lvls - 1]; \ + for ((rnp) = rcu_first_leaf_node(rsp); \ (rnp) < &(rsp)->node[rcu_num_nodes]; (rnp)++) /* @@ -486,6 +491,7 @@ void rcu_force_quiescent_state(void); void rcu_bh_force_quiescent_state(void); void rcu_sched_force_quiescent_state(void); extern struct workqueue_struct *rcu_gp_wq; +extern struct workqueue_struct *rcu_par_gp_wq; #endif /* #else #ifdef CONFIG_TINY_RCU */ #ifdef CONFIG_RCU_NOCB_CPU diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 88cba7c2956c..5aff271adf1e 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -404,24 +404,6 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq) } /* - * Scan the specified rcu_segcblist structure for callbacks that need - * a grace period later than the one specified by "seq". We don't look - * at the RCU_DONE_TAIL or RCU_NEXT_TAIL segments because they don't - * have a grace-period sequence number. - */ -bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp, - unsigned long seq) -{ - int i; - - for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) - if (rsclp->tails[i - 1] != rsclp->tails[i] && - ULONG_CMP_LT(seq, rsclp->gp_seq[i])) - return true; - return false; -} - -/* * Merge the source rcu_segcblist structure into the destination * rcu_segcblist structure, then initialize the source. Any pending * callbacks from the source get to start over. It is best to diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index 581c12b63544..948470cef385 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -134,7 +134,5 @@ void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp, struct rcu_cblist *rclp); void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq); bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq); -bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp, - unsigned long seq); void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp, struct rcu_segcblist *src_rsclp); diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index 777e7a6a0292..e232846516b3 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -369,7 +369,7 @@ static bool __maybe_unused torturing_tasks(void) */ static void rcu_perf_wait_shutdown(void) { - cond_resched_rcu_qs(); + cond_resched_tasks_rcu_qs(); if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters) return; while (!torture_must_stop()) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 680c96d8c00f..e628fcfd1bde 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -593,7 +593,12 @@ static void srcu_torture_init(void) static void srcu_torture_cleanup(void) { - cleanup_srcu_struct(&srcu_ctld); + static DEFINE_TORTURE_RANDOM(rand); + + if (torture_random(&rand) & 0x800) + cleanup_srcu_struct(&srcu_ctld); + else + cleanup_srcu_struct_quiesced(&srcu_ctld); srcu_ctlp = &srcu_ctl; /* In case of a later rcutorture run. */ } @@ -1609,6 +1614,9 @@ static enum cpuhp_state rcutor_hp; static void rcu_torture_cleanup(void) { + int flags = 0; + unsigned long gpnum = 0; + unsigned long completed = 0; int i; rcutorture_record_test_transition(); @@ -1639,6 +1647,11 @@ rcu_torture_cleanup(void) fakewriter_tasks = NULL; } + rcutorture_get_gp_data(cur_ops->ttype, &flags, &gpnum, &completed); + srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, + &flags, &gpnum, &completed); + pr_alert("%s: End-test grace-period state: g%lu c%lu f%#x\n", + cur_ops->name, gpnum, completed, flags); torture_stop_kthread(rcu_torture_stats, stats_task); torture_stop_kthread(rcu_torture_fqs, fqs_task); for (i = 0; i < ncbflooders; i++) diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 76ac5f50b2c7..622792abe41a 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -86,16 +86,19 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); * Must invoke this after you are finished using a given srcu_struct that * was initialized via init_srcu_struct(), else you leak memory. */ -void cleanup_srcu_struct(struct srcu_struct *sp) +void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) { WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]); - flush_work(&sp->srcu_work); + if (quiesced) + WARN_ON(work_pending(&sp->srcu_work)); + else + flush_work(&sp->srcu_work); WARN_ON(sp->srcu_gp_running); WARN_ON(sp->srcu_gp_waiting); WARN_ON(sp->srcu_cb_head); WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail); } -EXPORT_SYMBOL_GPL(cleanup_srcu_struct); +EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); /* * Removes the count for the old reader from the appropriate element of diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index fb560fca9ef4..b4123d7a2cec 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -366,24 +366,28 @@ static unsigned long srcu_get_delay(struct srcu_struct *sp) return SRCU_INTERVAL; } -/** - * cleanup_srcu_struct - deconstruct a sleep-RCU structure - * @sp: structure to clean up. - * - * Must invoke this after you are finished using a given srcu_struct that - * was initialized via init_srcu_struct(), else you leak memory. - */ -void cleanup_srcu_struct(struct srcu_struct *sp) +/* Helper for cleanup_srcu_struct() and cleanup_srcu_struct_quiesced(). */ +void _cleanup_srcu_struct(struct srcu_struct *sp, bool quiesced) { int cpu; if (WARN_ON(!srcu_get_delay(sp))) - return; /* Leakage unless caller handles error. */ + return; /* Just leak it! */ if (WARN_ON(srcu_readers_active(sp))) - return; /* Leakage unless caller handles error. */ - flush_delayed_work(&sp->work); + return; /* Just leak it! */ + if (quiesced) { + if (WARN_ON(delayed_work_pending(&sp->work))) + return; /* Just leak it! */ + } else { + flush_delayed_work(&sp->work); + } for_each_possible_cpu(cpu) - flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work); + if (quiesced) { + if (WARN_ON(delayed_work_pending(&per_cpu_ptr(sp->sda, cpu)->work))) + return; /* Just leak it! */ + } else { + flush_delayed_work(&per_cpu_ptr(sp->sda, cpu)->work); + } if (WARN_ON(rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)) != SRCU_STATE_IDLE) || WARN_ON(srcu_readers_active(sp))) { pr_info("%s: Active srcu_struct %p state: %d\n", __func__, sp, rcu_seq_state(READ_ONCE(sp->srcu_gp_seq))); @@ -392,7 +396,7 @@ void cleanup_srcu_struct(struct srcu_struct *sp) free_percpu(sp->sda); sp->sda = NULL; } -EXPORT_SYMBOL_GPL(cleanup_srcu_struct); +EXPORT_SYMBOL_GPL(_cleanup_srcu_struct); /* * Counts the new reader in the appropriate per-CPU element of the diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2a734692a581..aa7cade1b9f3 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -524,8 +524,6 @@ module_param(rcu_kick_kthreads, bool, 0644); static ulong jiffies_till_sched_qs = HZ / 10; module_param(jiffies_till_sched_qs, ulong, 0444); -static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp); static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)); static void force_quiescent_state(struct rcu_state *rsp); static int rcu_pending(void); @@ -711,44 +709,6 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp) } /* - * Is there any need for future grace periods? - * Interrupts must be disabled. If the caller does not hold the root - * rnp_node structure's ->lock, the results are advisory only. - */ -static int rcu_future_needs_gp(struct rcu_state *rsp) -{ - struct rcu_node *rnp = rcu_get_root(rsp); - int idx = (READ_ONCE(rnp->completed) + 1) & 0x1; - int *fp = &rnp->need_future_gp[idx]; - - lockdep_assert_irqs_disabled(); - return READ_ONCE(*fp); -} - -/* - * Does the current CPU require a not-yet-started grace period? - * The caller must have disabled interrupts to prevent races with - * normal callback registry. - */ -static bool -cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) -{ - lockdep_assert_irqs_disabled(); - if (rcu_gp_in_progress(rsp)) - return false; /* No, a grace period is already in progress. */ - if (rcu_future_needs_gp(rsp)) - return true; /* Yes, a no-CBs CPU needs one. */ - if (!rcu_segcblist_is_enabled(&rdp->cblist)) - return false; /* No, this is a no-CBs (or offline) CPU. */ - if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) - return true; /* Yes, CPU has newly registered callbacks. */ - if (rcu_segcblist_future_gp_needed(&rdp->cblist, - READ_ONCE(rsp->completed))) - return true; /* Yes, CBs for future grace period. */ - return false; /* No grace period needed. */ -} - -/* * Enter an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * @@ -1234,10 +1194,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) } /* - * Has this CPU encountered a cond_resched_rcu_qs() since the - * beginning of the grace period? For this to be the case, - * the CPU has to have noticed the current grace period. This - * might not be the case for nohz_full CPUs looping in the kernel. + * Has this CPU encountered a cond_resched() since the beginning + * of the grace period? For this to be the case, the CPU has to + * have noticed the current grace period. This might not be the + * case for nohz_full CPUs looping in the kernel. */ jtsq = jiffies_till_sched_qs; ruqp = per_cpu_ptr(&rcu_dynticks.rcu_urgent_qs, rdp->cpu); @@ -1642,18 +1602,30 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp, return rnp->completed + 1; /* + * If the current rcu_node structure believes that RCU is + * idle, and if the rcu_state structure does not yet reflect + * the start of a new grace period, then the next grace period + * will suffice. The memory barrier is needed to accurately + * sample the rsp->gpnum, and pairs with the second lock + * acquisition in rcu_gp_init(), which is augmented with + * smp_mb__after_unlock_lock() for this purpose. + */ + if (rnp->gpnum == rnp->completed) { + smp_mb(); /* See above block comment. */ + if (READ_ONCE(rsp->gpnum) == rnp->completed) + return rnp->completed + 1; + } + + /* * Otherwise, wait for a possible partial grace period and * then the subsequent full grace period. */ return rnp->completed + 2; } -/* - * Trace-event helper function for rcu_start_future_gp() and - * rcu_nocb_wait_gp(). - */ -static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, - unsigned long c, const char *s) +/* Trace-event wrapper function for trace_rcu_future_grace_period. */ +static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long c, const char *s) { trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed, c, rnp->level, @@ -1661,96 +1633,67 @@ static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, } /* - * Start some future grace period, as needed to handle newly arrived + * Start the specified grace period, as needed to handle newly arrived * callbacks. The required future grace periods are recorded in each - * rcu_node structure's ->need_future_gp field. Returns true if there + * rcu_node structure's ->need_future_gp[] field. Returns true if there * is reason to awaken the grace-period kthread. * - * The caller must hold the specified rcu_node structure's ->lock. + * The caller must hold the specified rcu_node structure's ->lock, which + * is why the caller is responsible for waking the grace-period kthread. */ -static bool __maybe_unused -rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, - unsigned long *c_out) +static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long c) { - unsigned long c; bool ret = false; - struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); - - raw_lockdep_assert_held_rcu_node(rnp); - - /* - * Pick up grace-period number for new callbacks. If this - * grace period is already marked as needed, return to the caller. - */ - c = rcu_cbs_completed(rdp->rsp, rnp); - trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); - if (rnp->need_future_gp[c & 0x1]) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); - goto out; - } + struct rcu_state *rsp = rdp->rsp; + struct rcu_node *rnp_root; /* - * If either this rcu_node structure or the root rcu_node structure - * believe that a grace period is in progress, then we must wait - * for the one following, which is in "c". Because our request - * will be noticed at the end of the current grace period, we don't - * need to explicitly start one. We only do the lockless check - * of rnp_root's fields if the current rcu_node structure thinks - * there is no grace period in flight, and because we hold rnp->lock, - * the only possible change is when rnp_root's two fields are - * equal, in which case rnp_root->gpnum might be concurrently - * incremented. But that is OK, as it will just result in our - * doing some extra useless work. + * Use funnel locking to either acquire the root rcu_node + * structure's lock or bail out if the need for this grace period + * has already been recorded -- or has already started. If there + * is already a grace period in progress in a non-leaf node, no + * recording is needed because the end of the grace period will + * scan the leaf rcu_node structures. Note that rnp->lock must + * not be released. */ - if (rnp->gpnum != rnp->completed || - READ_ONCE(rnp_root->gpnum) != READ_ONCE(rnp_root->completed)) { - rnp->need_future_gp[c & 0x1]++; - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); - goto out; + raw_lockdep_assert_held_rcu_node(rnp); + trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf")); + for (rnp_root = rnp; 1; rnp_root = rnp_root->parent) { + if (rnp_root != rnp) + raw_spin_lock_rcu_node(rnp_root); + WARN_ON_ONCE(ULONG_CMP_LT(rnp_root->gpnum + + need_future_gp_mask(), c)); + if (need_future_gp_element(rnp_root, c) || + ULONG_CMP_GE(rnp_root->gpnum, c) || + (rnp != rnp_root && + rnp_root->gpnum != rnp_root->completed)) { + trace_rcu_this_gp(rnp_root, rdp, c, TPS("Prestarted")); + goto unlock_out; + } + need_future_gp_element(rnp_root, c) = true; + if (rnp_root != rnp && rnp_root->parent != NULL) + raw_spin_unlock_rcu_node(rnp_root); + if (!rnp_root->parent) + break; /* At root, and perhaps also leaf. */ } - /* - * There might be no grace period in progress. If we don't already - * hold it, acquire the root rcu_node structure's lock in order to - * start one (if needed). - */ - if (rnp != rnp_root) - raw_spin_lock_rcu_node(rnp_root); - - /* - * Get a new grace-period number. If there really is no grace - * period in progress, it will be smaller than the one we obtained - * earlier. Adjust callbacks as needed. - */ - c = rcu_cbs_completed(rdp->rsp, rnp_root); - if (!rcu_is_nocb_cpu(rdp->cpu)) - (void)rcu_segcblist_accelerate(&rdp->cblist, c); - - /* - * If the needed for the required grace period is already - * recorded, trace and leave. - */ - if (rnp_root->need_future_gp[c & 0x1]) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); + /* If GP already in progress, just leave, otherwise start one. */ + if (rnp_root->gpnum != rnp_root->completed) { + trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedleafroot")); goto unlock_out; } - - /* Record the need for the future grace period. */ - rnp_root->need_future_gp[c & 0x1]++; - - /* If a grace period is not already in progress, start one. */ - if (rnp_root->gpnum != rnp_root->completed) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); - } else { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); - ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); + trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedroot")); + WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT); + if (!rsp->gp_kthread) { + trace_rcu_this_gp(rnp_root, rdp, c, TPS("NoGPkthread")); + goto unlock_out; } + trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("newreq")); + ret = true; /* Caller must wake GP kthread. */ unlock_out: if (rnp != rnp_root) raw_spin_unlock_rcu_node(rnp_root); -out: - if (c_out != NULL) - *c_out = c; return ret; } @@ -1758,16 +1701,16 @@ out: * Clean up any old requests for the just-ended grace period. Also return * whether any additional grace periods have been requested. */ -static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) +static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) { - int c = rnp->completed; - int needmore; + unsigned long c = rnp->completed; + bool needmore; struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - rnp->need_future_gp[c & 0x1] = 0; - needmore = rnp->need_future_gp[(c + 1) & 0x1]; - trace_rcu_future_gp(rnp, rdp, c, - needmore ? TPS("CleanupMore") : TPS("Cleanup")); + need_future_gp_element(rnp, c) = false; + needmore = need_any_future_gp(rnp); + trace_rcu_this_gp(rnp, rdp, c, + needmore ? TPS("CleanupMore") : TPS("Cleanup")); return needmore; } @@ -1802,6 +1745,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp) static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { + unsigned long c; bool ret = false; raw_lockdep_assert_held_rcu_node(rnp); @@ -1820,8 +1764,9 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, * accelerating callback invocation to an earlier grace-period * number. */ - if (rcu_segcblist_accelerate(&rdp->cblist, rcu_cbs_completed(rsp, rnp))) - ret = rcu_start_future_gp(rnp, rdp, NULL); + c = rcu_cbs_completed(rsp, rnp); + if (rcu_segcblist_accelerate(&rdp->cblist, c)) + ret = rcu_start_this_gp(rnp, rdp, c); /* Trace depending on how much we were able to accelerate. */ if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) @@ -2049,7 +1994,7 @@ static bool rcu_gp_init(struct rcu_state *rsp) rnp->level, rnp->grplo, rnp->grphi, rnp->qsmask); raw_spin_unlock_irq_rcu_node(rnp); - cond_resched_rcu_qs(); + cond_resched_tasks_rcu_qs(); |