From 309ba859b95085f61f4f2a154df6be9cb9713a12 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 11 Jul 2018 14:36:49 -0700 Subject: rcu: Eliminate synchronize_rcu_mult() Now that synchronize_rcu() waits for both RCU read-side critical sections and preempt-disabled regions of code, the sole caller of synchronize_rcu_mult() can be replaced by synchronize_rcu(). This patch makes this change and removes synchronize_rcu_mult(). Note that _wait_rcu_gp() still supports synchronize_rcu_mult(), and thus might be simplified in the future to take only take a single call_rcu() function rather than the current list of them. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate_wait.h | 17 ----------------- 1 file changed, 17 deletions(-) (limited to 'include/linux') diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index 8a16c3eb3dd0..c0578ba23c1a 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -31,21 +31,4 @@ do { \ #define wait_rcu_gp(...) _wait_rcu_gp(false, __VA_ARGS__) -/** - * synchronize_rcu_mult - Wait concurrently for multiple grace periods - * @...: List of call_rcu() functions for different grace periods to wait on - * - * This macro waits concurrently for multiple types of RCU grace periods. - * For example, synchronize_rcu_mult(call_rcu, call_rcu_tasks) would wait - * on concurrent RCU and RCU-tasks grace periods. Waiting on a give SRCU - * domain requires you to write a wrapper function for that SRCU domain's - * call_srcu() function, supplying the corresponding srcu_struct. - * - * If Tiny RCU, tell _wait_rcu_gp() does not bother waiting for RCU, - * given that anywhere synchronize_rcu_mult() can be called is automatically - * a grace period. - */ -#define synchronize_rcu_mult(...) \ - _wait_rcu_gp(IS_ENABLED(CONFIG_TINY_RCU), __VA_ARGS__) - #endif /* _LINUX_SCHED_RCUPDATE_WAIT_H */ -- cgit v1.2.3 From f3e763c3e544b73ae5c4a3842cedb9ff6ca37715 Mon Sep 17 00:00:00 2001 From: Randy Dunlap Date: Mon, 3 Sep 2018 12:45:45 -0700 Subject: srcu: Fix kernel-doc missing notation Fix kernel-doc warnings for missing parameter descriptions: ../include/linux/srcu.h:175: warning: Function parameter or member 'p' not described in 'srcu_dereference_notrace' ../include/linux/srcu.h:175: warning: Function parameter or member 'sp' not described in 'srcu_dereference_notrace' Fixes: 0b764a6e4e19d ("srcu: Add notrace variant of srcu_dereference") Signed-off-by: Randy Dunlap Cc: Lai Jiangshan Cc: "Paul E. McKenney" Cc: Josh Triplett Cc: Steven Rostedt Cc: Mathieu Desnoyers Cc: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux') diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 67135d4a8a30..ebd5f1511690 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -171,6 +171,9 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp) /** * srcu_dereference_notrace - no tracing and no lockdep calls from here + * @p: the pointer to fetch and protect for later dereferencing + * @sp: pointer to the srcu_struct, which is used to check that we + * really are in an SRCU read-side critical section. */ #define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1) -- cgit v1.2.3 From 05f415715ce45da07a0b1a5eac842765b733157f Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 16 Oct 2018 04:12:58 -0700 Subject: rcu: Speed up expedited GPs when interrupting RCU reader In PREEMPT kernels, an expedited grace period might send an IPI to a CPU that is executing an RCU read-side critical section. In that case, it would be nice if the rcu_read_unlock() directly interacted with the RCU core code to immediately report the quiescent state. And this does happen in the case where the reader has been preempted. But it would also be a nice performance optimization if immediate reporting also happened in the preemption-free case. This commit therefore adds an ->exp_hint field to the task_struct structure's ->rcu_read_unlock_special field. The IPI handler sets this hint when it has interrupted an RCU read-side critical section, and this causes the outermost rcu_read_unlock() call to invoke rcu_read_unlock_special(), which, if preemption is enabled, reports the quiescent state immediately. If preemption is disabled, then the report is required to be deferred until preemption (or bottom halves or interrupts or whatever) is re-enabled. Because this is a hint, it does nothing for more complicated cases. For example, if the IPI interrupts an RCU reader, but interrupts are disabled across the rcu_read_unlock(), but another rcu_read_lock() is executed before interrupts are re-enabled, the hint will already have been cleared. If you do crazy things like this, reporting will be deferred until some later RCU_SOFTIRQ handler, context switch, cond_resched(), or similar. Reported-by: Joel Fernandes Signed-off-by: Paul E. McKenney Acked-by: Joel Fernandes (Google) --- include/linux/sched.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index a51c13c2b1a0..e4c7b6241088 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -572,8 +572,10 @@ union rcu_special { struct { u8 blocked; u8 need_qs; + u8 exp_hint; /* Hint for performance. */ + u8 pad; /* No garbage from compiler! */ } b; /* Bits. */ - u16 s; /* Set of bits. */ + u32 s; /* Set of bits. */ }; enum perf_event_task_context { -- cgit v1.2.3 From 7440172974e85b1828bdd84ac6b23b5bcad9c5eb Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 6 Nov 2018 18:44:52 -0800 Subject: tracing: Replace synchronize_sched() and call_rcu_sched() Now that synchronize_rcu() waits for preempt-disable regions of code as well as RCU read-side critical sections, synchronize_sched() can be replaced by synchronize_rcu(). Similarly, call_rcu_sched() can be replaced by call_rcu(). This commit therefore makes these changes. Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Acked-by: Steven Rostedt (VMware) --- include/linux/tracepoint.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 538ba1a58f5b..432080b59c26 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -82,7 +82,7 @@ int unregister_tracepoint_module_notifier(struct notifier_block *nb) static inline void tracepoint_synchronize_unregister(void) { synchronize_srcu(&tracepoint_srcu); - synchronize_sched(); + synchronize_rcu(); } #else static inline void tracepoint_synchronize_unregister(void) -- cgit v1.2.3 From aacb5d91ab1bfbb0e8123da59a2e333d52ba7f60 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 28 Oct 2018 10:32:51 -0700 Subject: srcu: Use "ssp" instead of "sp" for srcu_struct pointer In RCU, the distinction between "rsp", "rnp", and "rdp" has served well for a great many years, but in SRCU, "sp" vs. "sdp" has proven confusing. This commit therefore renames SRCU's "sp" pointers to "ssp", so that there is "ssp" for srcu_struct pointer, "snp" for srcu_node pointer, and "sdp" for srcu_data pointer. Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 78 ++++++++++++++++++++++++------------------------ include/linux/srcutiny.h | 24 +++++++-------- include/linux/srcutree.h | 8 ++--- 3 files changed, 55 insertions(+), 55 deletions(-) (limited to 'include/linux') diff --git a/include/linux/srcu.h b/include/linux/srcu.h index ebd5f1511690..c614375cd264 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -38,20 +38,20 @@ struct srcu_struct; #ifdef CONFIG_DEBUG_LOCK_ALLOC -int __init_srcu_struct(struct srcu_struct *sp, const char *name, +int __init_srcu_struct(struct srcu_struct *ssp, const char *name, struct lock_class_key *key); -#define init_srcu_struct(sp) \ +#define init_srcu_struct(ssp) \ ({ \ static struct lock_class_key __srcu_key; \ \ - __init_srcu_struct((sp), #sp, &__srcu_key); \ + __init_srcu_struct((ssp), #ssp, &__srcu_key); \ }) #define __SRCU_DEP_MAP_INIT(srcu_name) .dep_map = { .name = #srcu_name }, #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -int init_srcu_struct(struct srcu_struct *sp); +int init_srcu_struct(struct srcu_struct *ssp); #define __SRCU_DEP_MAP_INIT(srcu_name) #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -67,28 +67,28 @@ int init_srcu_struct(struct srcu_struct *sp); struct srcu_struct { }; #endif -void call_srcu(struct srcu_struct *sp, struct rcu_head *head, +void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, void (*func)(struct rcu_head *head)); -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); +void _cleanup_srcu_struct(struct srcu_struct *ssp, bool quiesced); +int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); +void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); +void synchronize_srcu(struct srcu_struct *ssp); /** * cleanup_srcu_struct - deconstruct a sleep-RCU structure - * @sp: structure to clean up. + * @ssp: 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) +static inline void cleanup_srcu_struct(struct srcu_struct *ssp) { - _cleanup_srcu_struct(sp, false); + _cleanup_srcu_struct(ssp, false); } /** * cleanup_srcu_struct_quiesced - deconstruct a quiesced sleep-RCU structure - * @sp: structure to clean up. + * @ssp: 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, @@ -103,16 +103,16 @@ static inline void cleanup_srcu_struct(struct srcu_struct *sp) * (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) +static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *ssp) { - _cleanup_srcu_struct(sp, true); + _cleanup_srcu_struct(ssp, true); } #ifdef CONFIG_DEBUG_LOCK_ALLOC /** * srcu_read_lock_held - might we be in SRCU read-side critical section? - * @sp: The srcu_struct structure to check + * @ssp: The srcu_struct structure to check * * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, @@ -126,16 +126,16 @@ static inline void cleanup_srcu_struct_quiesced(struct srcu_struct *sp) * relies on normal RCU, it can be called from the CPU which * is in the idle loop from an RCU point of view or offline. */ -static inline int srcu_read_lock_held(const struct srcu_struct *sp) +static inline int srcu_read_lock_held(const struct srcu_struct *ssp) { if (!debug_lockdep_rcu_enabled()) return 1; - return lock_is_held(&sp->dep_map); + return lock_is_held(&ssp->dep_map); } #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -static inline int srcu_read_lock_held(const struct srcu_struct *sp) +static inline int srcu_read_lock_held(const struct srcu_struct *ssp) { return 1; } @@ -145,7 +145,7 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp) /** * srcu_dereference_check - fetch SRCU-protected pointer for later dereferencing * @p: the pointer to fetch and protect for later dereferencing - * @sp: pointer to the srcu_struct, which is used to check that we + * @ssp: pointer to the srcu_struct, which is used to check that we * really are in an SRCU read-side critical section. * @c: condition to check for update-side use * @@ -154,32 +154,32 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp) * to 1. The @c argument will normally be a logical expression containing * lockdep_is_held() calls. */ -#define srcu_dereference_check(p, sp, c) \ - __rcu_dereference_check((p), (c) || srcu_read_lock_held(sp), __rcu) +#define srcu_dereference_check(p, ssp, c) \ + __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu) /** * srcu_dereference - fetch SRCU-protected pointer for later dereferencing * @p: the pointer to fetch and protect for later dereferencing - * @sp: pointer to the srcu_struct, which is used to check that we + * @ssp: pointer to the srcu_struct, which is used to check that we * really are in an SRCU read-side critical section. * * Makes rcu_dereference_check() do the dirty work. If PROVE_RCU * is enabled, invoking this outside of an RCU read-side critical * section will result in an RCU-lockdep splat. */ -#define srcu_dereference(p, sp) srcu_dereference_check((p), (sp), 0) +#define srcu_dereference(p, ssp) srcu_dereference_check((p), (ssp), 0) /** * srcu_dereference_notrace - no tracing and no lockdep calls from here * @p: the pointer to fetch and protect for later dereferencing - * @sp: pointer to the srcu_struct, which is used to check that we + * @ssp: pointer to the srcu_struct, which is used to check that we * really are in an SRCU read-side critical section. */ -#define srcu_dereference_notrace(p, sp) srcu_dereference_check((p), (sp), 1) +#define srcu_dereference_notrace(p, ssp) srcu_dereference_check((p), (ssp), 1) /** * srcu_read_lock - register a new reader for an SRCU-protected structure. - * @sp: srcu_struct in which to register the new reader. + * @ssp: srcu_struct in which to register the new reader. * * Enter an SRCU read-side critical section. Note that SRCU read-side * critical sections may be nested. However, it is illegal to @@ -194,44 +194,44 @@ static inline int srcu_read_lock_held(const struct srcu_struct *sp) * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() * was invoked in process context. */ -static inline int srcu_read_lock(struct srcu_struct *sp) __acquires(sp) +static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) { int retval; - retval = __srcu_read_lock(sp); - rcu_lock_acquire(&(sp)->dep_map); + retval = __srcu_read_lock(ssp); + rcu_lock_acquire(&(ssp)->dep_map); return retval; } /* Used by tracing, cannot be traced and cannot invoke lockdep. */ static inline notrace int -srcu_read_lock_notrace(struct srcu_struct *sp) __acquires(sp) +srcu_read_lock_notrace(struct srcu_struct *ssp) __acquires(ssp) { int retval; - retval = __srcu_read_lock(sp); + retval = __srcu_read_lock(ssp); return retval; } /** * srcu_read_unlock - unregister a old reader from an SRCU-protected structure. - * @sp: srcu_struct in which to unregister the old reader. + * @ssp: srcu_struct in which to unregister the old reader. * @idx: return value from corresponding srcu_read_lock(). * * Exit an SRCU read-side critical section. */ -static inline void srcu_read_unlock(struct srcu_struct *sp, int idx) - __releases(sp) +static inline void srcu_read_unlock(struct srcu_struct *ssp, int idx) + __releases(ssp) { - rcu_lock_release(&(sp)->dep_map); - __srcu_read_unlock(sp, idx); + rcu_lock_release(&(ssp)->dep_map); + __srcu_read_unlock(ssp, idx); } /* Used by tracing, cannot be traced and cannot call lockdep. */ static inline notrace void -srcu_read_unlock_notrace(struct srcu_struct *sp, int idx) __releases(sp) +srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) { - __srcu_read_unlock(sp, idx); + __srcu_read_unlock(ssp, idx); } /** diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index f41d2fb09f87..b19216aaaef2 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -60,7 +60,7 @@ void srcu_drive_gp(struct work_struct *wp); #define DEFINE_STATIC_SRCU(name) \ static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name) -void synchronize_srcu(struct srcu_struct *sp); +void synchronize_srcu(struct srcu_struct *ssp); /* * Counts the new reader in the appropriate per-CPU element of the @@ -68,36 +68,36 @@ void synchronize_srcu(struct srcu_struct *sp); * __srcu_read_unlock() must be in the same handler instance. Returns an * index that must be passed to the matching srcu_read_unlock(). */ -static inline int __srcu_read_lock(struct srcu_struct *sp) +static inline int __srcu_read_lock(struct srcu_struct *ssp) { int idx; - idx = READ_ONCE(sp->srcu_idx); - WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1); + idx = READ_ONCE(ssp->srcu_idx); + WRITE_ONCE(ssp->srcu_lock_nesting[idx], ssp->srcu_lock_nesting[idx] + 1); return idx; } -static inline void synchronize_srcu_expedited(struct srcu_struct *sp) +static inline void synchronize_srcu_expedited(struct srcu_struct *ssp) { - synchronize_srcu(sp); + synchronize_srcu(ssp); } -static inline void srcu_barrier(struct srcu_struct *sp) +static inline void srcu_barrier(struct srcu_struct *ssp) { - synchronize_srcu(sp); + synchronize_srcu(ssp); } /* Defined here to avoid size increase for non-torture kernels. */ -static inline void srcu_torture_stats_print(struct srcu_struct *sp, +static inline void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf) { int idx; - idx = READ_ONCE(sp->srcu_idx) & 0x1; + idx = READ_ONCE(ssp->srcu_idx) & 0x1; pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n", tt, tf, idx, - READ_ONCE(sp->srcu_lock_nesting[!idx]), - READ_ONCE(sp->srcu_lock_nesting[idx])); + READ_ONCE(ssp->srcu_lock_nesting[!idx]), + READ_ONCE(ssp->srcu_lock_nesting[idx])); } #endif diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 0ae91b3a7406..6f292bd3e7db 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -51,7 +51,7 @@ struct srcu_data { unsigned long grpmask; /* Mask for leaf srcu_node */ /* ->srcu_data_have_cbs[]. */ int cpu; - struct srcu_struct *sp; + struct srcu_struct *ssp; }; /* @@ -138,8 +138,8 @@ struct srcu_struct { #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) -void synchronize_srcu_expedited(struct srcu_struct *sp); -void srcu_barrier(struct srcu_struct *sp); -void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf); +void synchronize_srcu_expedited(struct srcu_struct *ssp); +void srcu_barrier(struct srcu_struct *ssp); +void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); #endif -- cgit v1.2.3 From e3e740544173ef0dd8bffbf158182a7748e6c678 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 7 Nov 2018 13:53:34 -0800 Subject: percpu-rwsem: Replace synchronize_sched() with synchronize_rcu() Now that synchronize_rcu() waits for preempt-disable regions of code as well as RCU read-side critical sections, synchronize_sched() can be replaced by synchronize_rcu(). This commit therefore makes this change, even though it is but a comment. Signed-off-by: Paul E. McKenney Cc: Dennis Zhou Cc: Christoph Lameter Acked-by: Tejun Heo --- include/linux/percpu-rwsem.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include/linux') diff --git a/include/linux/percpu-rwsem.h b/include/linux/percpu-rwsem.h index 79b99d653e03..71b75643c432 100644 --- a/include/linux/percpu-rwsem.h +++ b/include/linux/percpu-rwsem.h @@ -41,7 +41,7 @@ static inline void percpu_down_read_preempt_disable(struct percpu_rw_semaphore * * cannot both change sem->state from readers_fast and start checking * counters while we are here. So if we see !sem->state, we know that * the writer won't be checking until we're past the preempt_enable() - * and that one the synchronize_sched() is done, the writer will see + * and that once the synchronize_rcu() is done, the writer will see * anything we did within this RCU-sched read-size critical section. */ __this_cpu_inc(*sem->read_count); -- cgit v1.2.3 From d5cccfc7b772b8a20b06557f1b7c066e7fc2c393 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 7 Nov 2018 14:01:39 -0800 Subject: types: Remove call_rcu_bh() and call_rcu_sched() Now that call_rcu()'s callback is not invoked until after bh-disable and preempt-disable regions of code have completed (in addition to explicitly marked RCU read-side critical sections), call_rcu() can be used in place of call_rcu_bh() and call_rcu_sched(). This commit therefore removes these two API members from the callback_head structure's header comment. Signed-off-by: Paul E. McKenney Cc: Andrew Morton Cc: Pekka Enberg Cc: Masahiro Yamada Cc: Alexey Dobriyan --- include/linux/types.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/types.h b/include/linux/types.h index 9834e90aa010..c2615d6a019e 100644 --- a/include/linux/types.h +++ b/include/linux/types.h @@ -212,8 +212,8 @@ struct ustat { * weird ABI and we need to ask it explicitly. * * The alignment is required to guarantee that bit 0 of @next will be - * clear under normal conditions -- as long as we use call_rcu(), - * call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback. + * clear under normal conditions -- as long as we use call_rcu() or + * call_srcu() to queue the callback. * * This guarantee is important for few reasons: * - future call_rcu_lazy() will make use of lower bits in the pointer; -- cgit v1.2.3