From 1b27291b1ea4f1f2090fb07c3425db474cdb99ba Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 18 Jul 2018 14:32:31 -0700 Subject: rcutorture: Add forward-progress tests for RCU grace periods This commit adds a kthread that loops going into and out of RCU read-side critical sections, but also including a cond_resched(), optionally guarded by a check of need_resched(), in that same loop. This commit relies solely on rcu_torture_writer() progress to judge the forward progress of grace periods. Note that Tasks RCU and SRCU are exempted from forward-progress testing due their (intentionally) less-robust forward-progress guarantees. Signed-off-by: Paul E. McKenney --- include/linux/rcutiny.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 8d9a0ea8f0b5..a6353f3d6094 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -108,6 +108,7 @@ static inline int rcu_needs_cpu(u64 basemono, u64 *nextevt) */ static inline void rcu_virt_note_context_switch(int cpu) { } static inline void rcu_cpu_stall_reset(void) { } +static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; } static inline void rcu_idle_enter(void) { } static inline void rcu_idle_exit(void) { } static inline void rcu_irq_enter(void) { } -- cgit v1.2.3 From 474e59b476b3390ef9f730515439f21640b61623 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 7 Aug 2018 14:34:44 -0700 Subject: rcutorture: Check GP completion at stutter end The rcu_torture_writer() function invokes stutter_wait() at the end of each writer pass, which occasionally blocks for an extended time period in order to ensure that RCU can handle intermittent loads. But part of handling a busy period is invoking all the callbacks before the end of the idle period induced by stutter_wait(). This commit therefore adds a return value to stutter_wait() indicating whether stutter_wait() actually waited. In addition, this commit causes rcu_torture_writer() to test this value and if set, checks that all the elements of the rcu_tortures[] array have been freed up. Signed-off-by: Paul E. McKenney --- include/linux/torture.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/torture.h b/include/linux/torture.h index 61dfd93b6ee4..48fad21109fc 100644 --- a/include/linux/torture.h +++ b/include/linux/torture.h @@ -77,7 +77,7 @@ void torture_shutdown_absorb(const char *title); int torture_shutdown_init(int ssecs, void (*cleanup)(void)); /* Task stuttering, which forces load/no-load transitions. */ -void stutter_wait(const char *title); +bool stutter_wait(const char *title); int torture_stutter_init(int s); /* Initialization and cleanup. */ -- cgit v1.2.3 From 3e31009898699dfca823893054748d85048dc7b3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 21 Jun 2018 12:50:01 -0700 Subject: rcu: Defer reporting RCU-preempt quiescent states when disabled This commit defers reporting of RCU-preempt quiescent states at rcu_read_unlock_special() time when any of interrupts, softirq, or preemption are disabled. These deferred quiescent states are reported at a later RCU_SOFTIRQ, context switch, idle entry, or CPU-hotplug offline operation. Of course, if another RCU read-side critical section has started in the meantime, the reporting of the quiescent state will be further deferred. This also means that disabling preemption, interrupts, and/or softirqs will act as an RCU-preempt read-side critical section. This is enforced by checking preempt_count() as needed. Some special cases must be handled on an ad-hoc basis, for example, context switch is a quiescent state even though both the scheduler and do_exit() disable preemption. In these cases, additional calls to rcu_preempt_deferred_qs() override the preemption disabling. Similar logic overrides disabled interrupts in rcu_preempt_check_callbacks() because in this case the quiescent state happened just before the corresponding scheduling-clock interrupt. In theory, this change lifts a long-standing restriction that required that if interrupts were disabled across a call to rcu_read_unlock() that the matching rcu_read_lock() also be contained within that interrupts-disabled region of code. Because the reporting of the corresponding RCU-preempt quiescent state is now deferred until after interrupts have been enabled, it is no longer possible for this situation to result in deadlocks involving the scheduler's runqueue and priority-inheritance locks. This may allow some code simplification that might reduce interrupt latency a bit. Unfortunately, in practice this would also defer deboosting a low-priority task that had been subjected to RCU priority boosting, so real-time-response considerations might well force this restriction to remain in place. Because RCU-preempt grace periods are now blocked not only by RCU read-side critical sections, but also by disabling of interrupts, preemption, and softirqs, it will be possible to eliminate RCU-bh and RCU-sched in favor of RCU-preempt in CONFIG_PREEMPT=y kernels. This may require some additional plumbing to provide the network denial-of-service guarantees that have been traditionally provided by RCU-bh. Once these are in place, CONFIG_PREEMPT=n kernels will be able to fold RCU-bh into RCU-sched. This would mean that all kernels would have but one flavor of RCU, which would open the door to significant code cleanup. Moving to a single flavor of RCU would also have the beneficial effect of reducing the NOCB kthreads by at least a factor of two. Signed-off-by: Paul E. McKenney [ paulmck: Apply rcu_read_unlock_special() preempt_count() feedback from Joel Fernandes. ] [ paulmck: Adjust rcu_eqs_enter() call to rcu_preempt_deferred_qs() in response to bug reports from kbuild test robot. ] [ paulmck: Fix bug located by kbuild test robot involving recursion via rcu_preempt_deferred_qs(). ] --- include/linux/rcutiny.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 8d9a0ea8f0b5..f617ab19bb51 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -115,6 +115,11 @@ static inline void rcu_irq_exit_irqson(void) { } static inline void rcu_irq_enter_irqson(void) { } static inline void rcu_irq_exit(void) { } static inline void exit_rcu(void) { } +static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t) +{ + return false; +} +static inline void rcu_preempt_deferred_qs(struct task_struct *t) { } #ifdef CONFIG_SRCU void rcu_scheduler_starting(void); #else /* #ifndef CONFIG_SRCU */ -- cgit v1.2.3 From fcc878e4dfb70128a73857c609d70570629b0d9e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 28 Jun 2018 07:39:59 -0700 Subject: rcu: Remove now-unused ->b.exp_need_qs field from the rcu_special union The ->b.exp_need_qs field is now set only to false, so this commit removes it. The job this field used to do is now done by the rcu_data structure's ->deferred_qs field, which is a consequence of a better split between task-based (the rcu_node structure's ->exp_tasks field) and CPU-based (the aforementioned rcu_data structure's ->deferred_qs field) tracking of quiescent states for RCU-preempt expedited grace periods. Signed-off-by: Paul E. McKenney --- include/linux/sched.h | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 977cb57d7bc9..004ca21f7e80 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -571,12 +571,8 @@ union rcu_special { struct { u8 blocked; u8 need_qs; - u8 exp_need_qs; - - /* Otherwise the compiler can store garbage here: */ - u8 pad; } b; /* Bits. */ - u32 s; /* Set of bits. */ + u16 s; /* Set of bits. */ }; enum perf_event_task_context { -- cgit v1.2.3 From d28139c4e96713d52a300fb9036c5be2f45e0741 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 28 Jun 2018 14:45:25 -0700 Subject: rcu: Apply RCU-bh QSes to RCU-sched and RCU-preempt when safe One necessary step towards consolidating the three flavors of RCU is to make sure that the resulting consolidated "one flavor to rule them all" correctly handles networking denial-of-service attacks. One thing that allows RCU-bh to do so is that __do_softirq() invokes rcu_bh_qs() every so often, and so something similar has to happen for consolidated RCU. This must be done carefully. For example, if a preemption-disabled region of code takes an interrupt which does softirq processing before returning, consolidated RCU must ignore the resulting rcu_bh_qs() invocations -- preemption is still disabled, and that means an RCU reader for the consolidated flavor. This commit therefore creates a new rcu_softirq_qs() that is called only from the ksoftirqd task, thus avoiding the interrupted-a-preempted-region problem. This new rcu_softirq_qs() function invokes rcu_sched_qs(), rcu_preempt_qs(), and rcu_preempt_deferred_qs(). The latter call handles any deferred quiescent states. Note that __do_softirq() still invokes rcu_bh_qs(). It will continue to do so until a later stage of cleanup when the RCU-bh flavor is removed. Signed-off-by: Paul E. McKenney [ paulmck: Fix !SMP issue located by kbuild test robot. ] --- include/linux/rcutiny.h | 5 +++++ include/linux/rcutree.h | 1 + 2 files changed, 6 insertions(+) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index f617ab19bb51..bcfbc40a7239 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -90,6 +90,11 @@ static inline void kfree_call_rcu(struct rcu_head *head, call_rcu(head, func); } +static inline void rcu_softirq_qs(void) +{ + rcu_sched_qs(); +} + #define rcu_note_context_switch(preempt) \ do { \ rcu_sched_qs(); \ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 914655848ef6..664b580695d6 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -30,6 +30,7 @@ #ifndef __LINUX_RCUTREE_H #define __LINUX_RCUTREE_H +void rcu_softirq_qs(void); void rcu_note_context_switch(bool preempt); int rcu_needs_cpu(u64 basem, u64 *nextevt); void rcu_cpu_stall_reset(void); -- cgit v1.2.3 From 65cfe3583b612a22e12fba9a7bbd2d37ca5ad941 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 1 Jul 2018 07:40:52 -0700 Subject: rcu: Define RCU-bh update API in terms of RCU Now that the main RCU API knows about softirq disabling and softirq's quiescent states, the RCU-bh update code can be dispensed with. This commit therefore removes the RCU-bh update-side implementation and defines RCU-bh's update-side API in terms of that of either RCU-preempt or RCU-sched, depending on the setting of the CONFIG_PREEMPT Kconfig option. In kernels built with CONFIG_RCU_NOCB_CPU=y this has the knock-on effect of reducing by one the number of rcuo kthreads per CPU. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 10 ++++++---- include/linux/rcutiny.h | 10 +++++++--- include/linux/rcutree.h | 8 ++++++-- 3 files changed, 19 insertions(+), 9 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 75e5b393cf44..9ebfd436cec7 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -55,11 +55,15 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func); #define call_rcu call_rcu_sched #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ -void call_rcu_bh(struct rcu_head *head, rcu_callback_t func); void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); void synchronize_sched(void); void rcu_barrier_tasks(void); +static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) +{ + call_rcu(head, func); +} + #ifdef CONFIG_PREEMPT_RCU void __rcu_read_lock(void); @@ -104,7 +108,6 @@ static inline int rcu_preempt_depth(void) void rcu_init(void); extern int rcu_scheduler_active __read_mostly; void rcu_sched_qs(void); -void rcu_bh_qs(void); void rcu_check_callbacks(int user); void rcu_report_dead(unsigned int cpu); void rcutree_migrate_callbacks(int cpu); @@ -326,8 +329,7 @@ static inline void rcu_preempt_sleep_check(void) { } * and rcu_assign_pointer(). Some of these could be folded into their * callers, but they are left separate in order to ease introduction of * multiple flavors of pointers to match the multiple flavors of RCU - * (e.g., __rcu_bh, * __rcu_sched, and __srcu), should this make sense in - * the future. + * (e.g., __rcu_sched, and __srcu), should this make sense in the future. */ #ifdef __CHECKER__ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index bcfbc40a7239..ac26c27ccde8 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -56,19 +56,23 @@ static inline void cond_synchronize_sched(unsigned long oldstate) might_sleep(); } -extern void rcu_barrier_bh(void); -extern void rcu_barrier_sched(void); - static inline void synchronize_rcu_expedited(void) { synchronize_sched(); /* Only one CPU, so pretty fast anyway!!! */ } +extern void rcu_barrier_sched(void); + static inline void rcu_barrier(void) { rcu_barrier_sched(); /* Only one CPU, so only one list of callbacks! */ } +static inline void rcu_barrier_bh(void) +{ + rcu_barrier(); +} + static inline void synchronize_rcu_bh(void) { synchronize_sched(); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 664b580695d6..c789c302a2c9 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,7 +45,11 @@ static inline void rcu_virt_note_context_switch(int cpu) rcu_note_context_switch(false); } -void synchronize_rcu_bh(void); +static inline void synchronize_rcu_bh(void) +{ + synchronize_rcu(); +} + void synchronize_sched_expedited(void); void synchronize_rcu_expedited(void); @@ -69,7 +73,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); */ static inline void synchronize_rcu_bh_expedited(void) { - synchronize_sched_expedited(); + synchronize_rcu_expedited(); } void rcu_barrier(void); -- cgit v1.2.3 From 82fcecfa81855924cc69f3078113cf63dd6c2964 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 2 Jul 2018 09:04:27 -0700 Subject: rcu: Update comments and help text for no more RCU-bh updaters This commit updates comments and help text to account for the fact that RCU-bh update-side functions are now simple wrappers for their RCU or RCU-sched counterparts. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 12 ++++-------- include/linux/rcupdate_wait.h | 6 +++--- include/linux/rcutree.h | 14 ++------------ 3 files changed, 9 insertions(+), 23 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9ebfd436cec7..8d5740edd63c 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -688,14 +688,10 @@ static inline void rcu_read_unlock(void) /** * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section * - * This is equivalent of rcu_read_lock(), but to be used when updates - * are being done using call_rcu_bh() or synchronize_rcu_bh(). Since - * both call_rcu_bh() and synchronize_rcu_bh() consider completion of a - * softirq handler to be a quiescent state, a process in RCU read-side - * critical section must be protected by disabling softirqs. Read-side - * critical sections in interrupt context can use just rcu_read_lock(), - * though this should at least be commented to avoid confusing people - * reading the code. + * This is equivalent of rcu_read_lock(), but also disables softirqs. + * Note that synchronize_rcu() and friends may be used for the update + * side, although synchronize_rcu_bh() is available as a wrapper in the + * short term. Longer term, the _bh update-side API will be eliminated. * * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() * must occur in the same context, for example, it is illegal to invoke diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index 57f371344152..bc104699560e 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -36,13 +36,13 @@ do { \ * @...: List of call_rcu() functions for the flavors to wait on. * * This macro waits concurrently for multiple flavors of RCU grace periods. - * For example, synchronize_rcu_mult(call_rcu, call_rcu_bh) would wait - * on concurrent RCU and RCU-bh grace periods. Waiting on a give SRCU + * For example, synchronize_rcu_mult(call_rcu, call_rcu_sched) would wait + * on concurrent RCU and RCU-sched 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() not to bother waiting for RCU - * or RCU-bh, given that anywhere synchronize_rcu_mult() can be called + * or RCU-sched, given that anywhere synchronize_rcu_mult() can be called * is automatically a grace period. */ #define synchronize_rcu_mult(...) \ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index c789c302a2c9..f7a41323aa54 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -58,18 +58,8 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); /** * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period * - * Wait for an RCU-bh grace period to elapse, but use a "big hammer" - * approach to force the grace period to end quickly. This consumes - * significant time on all CPUs and is unfriendly to real-time workloads, - * so is thus not recommended for any sort of common-case code. In fact, - * if you are using synchronize_rcu_bh_expedited() in a loop, please - * restructure your code to batch your updates, and then use a single - * synchronize_rcu_bh() instead. - * - * Note that it is illegal to call this function while holding any lock - * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal - * to call this function from a CPU-hotplug notifier. Failing to observe - * these restriction will result in deadlock. + * This is a transitional API and will soon be removed, with all + * callers converted to synchronize_rcu_expedited(). */ static inline void synchronize_rcu_bh_expedited(void) { -- cgit v1.2.3 From 45975c7d21a1c0aba97e3d8007e2a7c123145748 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 2 Jul 2018 14:30:37 -0700 Subject: rcu: Define RCU-sched API in terms of RCU for Tree RCU PREEMPT builds Now that RCU-preempt knows about preemption disabling, its implementation of synchronize_rcu() works for synchronize_sched(), and likewise for the other RCU-sched update-side API members. This commit therefore confines the RCU-sched update-side code to CONFIG_PREEMPT=n builds, and defines RCU-sched's update-side API members in terms of those of RCU-preempt. This means that any given build of the Linux kernel has only one update-side flavor of RCU, namely RCU-preempt for CONFIG_PREEMPT=y builds and RCU-sched for CONFIG_PREEMPT=n builds. This in turn means that kernels built with CONFIG_RCU_NOCB_CPU=y have only one rcuo kthread per CPU. Signed-off-by: Paul E. McKenney Cc: Andi Kleen --- include/linux/rcupdate.h | 14 ++++---------- include/linux/rcutiny.h | 7 +++++++ include/linux/rcutree.h | 7 ++++++- 3 files changed, 17 insertions(+), 11 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 8d5740edd63c..94474bb6b5c4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -49,11 +49,11 @@ /* Exported common interfaces */ -#ifdef CONFIG_PREEMPT_RCU -void call_rcu(struct rcu_head *head, rcu_callback_t func); -#else /* #ifdef CONFIG_PREEMPT_RCU */ +#ifdef CONFIG_TINY_RCU #define call_rcu call_rcu_sched -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */ +#else +void call_rcu(struct rcu_head *head, rcu_callback_t func); +#endif void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); void synchronize_sched(void); @@ -92,11 +92,6 @@ static inline void __rcu_read_unlock(void) preempt_enable(); } -static inline void synchronize_rcu(void) -{ - synchronize_sched(); -} - static inline int rcu_preempt_depth(void) { return 0; @@ -107,7 +102,6 @@ static inline int rcu_preempt_depth(void) /* Internal to kernel */ void rcu_init(void); extern int rcu_scheduler_active __read_mostly; -void rcu_sched_qs(void); void rcu_check_callbacks(int user); void rcu_report_dead(unsigned int cpu); void rcutree_migrate_callbacks(int cpu); diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index ac26c27ccde8..df2c0895c5e7 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -36,6 +36,11 @@ static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp) /* Never flag non-existent other CPUs! */ static inline bool rcu_eqs_special_set(int cpu) { return false; } +static inline void synchronize_rcu(void) +{ + synchronize_sched(); +} + static inline unsigned long get_state_synchronize_rcu(void) { return 0; @@ -94,6 +99,8 @@ static inline void kfree_call_rcu(struct rcu_head *head, call_rcu(head, func); } +void rcu_sched_qs(void); + static inline void rcu_softirq_qs(void) { rcu_sched_qs(); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index f7a41323aa54..0c44720f0e84 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,14 +45,19 @@ static inline void rcu_virt_note_context_switch(int cpu) rcu_note_context_switch(false); } +void synchronize_rcu(void); static inline void synchronize_rcu_bh(void) { synchronize_rcu(); } -void synchronize_sched_expedited(void); void synchronize_rcu_expedited(void); +static inline void synchronize_sched_expedited(void) +{ + synchronize_rcu_expedited(); +} + void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); /** -- cgit v1.2.3 From 709fdce7545c978e69f52eb19082ea3af44332f5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 3 Jul 2018 10:44:44 -0700 Subject: rcu: Express Tiny RCU updates in terms of RCU rather than RCU-sched This commit renames Tiny RCU functions so that the lowest level of functionality is RCU (e.g., synchronize_rcu()) rather than RCU-sched (e.g., synchronize_sched()). This provides greater naming compatibility with Tree RCU, which will in turn permit more LoC removal once the RCU-sched and RCU-bh update-side API is removed. Signed-off-by: Paul E. McKenney [ paulmck: Fix Tiny call_rcu()'s EXPORT_SYMBOL() in response to a bug report from kbuild test robot. ] --- include/linux/rcupdate.h | 12 +++++------- include/linux/rcutiny.h | 34 +++++++++++++++++++--------------- include/linux/rcutree.h | 1 - 3 files changed, 24 insertions(+), 23 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 94474bb6b5c4..1207c6c9bd8b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -49,15 +49,14 @@ /* Exported common interfaces */ -#ifdef CONFIG_TINY_RCU -#define call_rcu call_rcu_sched -#else -void call_rcu(struct rcu_head *head, rcu_callback_t func); +#ifndef CONFIG_TINY_RCU +void synchronize_sched(void); +void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); #endif -void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); -void synchronize_sched(void); +void call_rcu(struct rcu_head *head, rcu_callback_t func); void rcu_barrier_tasks(void); +void synchronize_rcu(void); static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) { @@ -68,7 +67,6 @@ static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) void __rcu_read_lock(void); void __rcu_read_unlock(void); -void synchronize_rcu(void); /* * Defined as a macro as it is a very low level header included from diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index df2c0895c5e7..e66fb8bc2127 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -36,9 +36,9 @@ static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp) /* Never flag non-existent other CPUs! */ static inline bool rcu_eqs_special_set(int cpu) { return false; } -static inline void synchronize_rcu(void) +static inline void synchronize_sched(void) { - synchronize_sched(); + synchronize_rcu(); } static inline unsigned long get_state_synchronize_rcu(void) @@ -61,16 +61,11 @@ static inline void cond_synchronize_sched(unsigned long oldstate) might_sleep(); } -static inline void synchronize_rcu_expedited(void) -{ - synchronize_sched(); /* Only one CPU, so pretty fast anyway!!! */ -} +extern void rcu_barrier(void); -extern void rcu_barrier_sched(void); - -static inline void rcu_barrier(void) +static inline void rcu_barrier_sched(void) { - rcu_barrier_sched(); /* Only one CPU, so only one list of callbacks! */ + rcu_barrier(); /* Only one CPU, so only one list of callbacks! */ } static inline void rcu_barrier_bh(void) @@ -88,27 +83,36 @@ static inline void synchronize_rcu_bh_expedited(void) synchronize_sched(); } +static inline void synchronize_rcu_expedited(void) +{ + synchronize_sched(); +} + static inline void synchronize_sched_expedited(void) { synchronize_sched(); } -static inline void kfree_call_rcu(struct rcu_head *head, - rcu_callback_t func) +static inline void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) +{ + call_rcu(head, func); +} + +static inline void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) { call_rcu(head, func); } -void rcu_sched_qs(void); +void rcu_qs(void); static inline void rcu_softirq_qs(void) { - rcu_sched_qs(); + rcu_qs(); } #define rcu_note_context_switch(preempt) \ do { \ - rcu_sched_qs(); \ + rcu_qs(); \ rcu_tasks_qs(current); \ } while (0) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 0c44720f0e84..6d30a0809300 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,7 +45,6 @@ static inline void rcu_virt_note_context_switch(int cpu) rcu_note_context_switch(false); } -void synchronize_rcu(void); static inline void synchronize_rcu_bh(void) { synchronize_rcu(); -- cgit v1.2.3 From 4c7e9c1434c6fc960774a5475f2fbccbf557fdeb Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 6 Jul 2018 09:54:25 -0700 Subject: rcu: Consolidate RCU-bh update-side function definitions This commit saves a few lines by consolidating the RCU-bh function definitions at the end of include/linux/rcupdate.h. This consolidation also makes it easier to remove them all when the time comes. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 27 ++++++++++++++++++++++----- include/linux/rcutiny.h | 15 --------------- include/linux/rcutree.h | 17 ----------------- 3 files changed, 22 insertions(+), 37 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1207c6c9bd8b..e530f5739033 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -58,11 +58,6 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func); void rcu_barrier_tasks(void); void synchronize_rcu(void); -static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) -{ - call_rcu(head, func); -} - #ifdef CONFIG_PREEMPT_RCU void __rcu_read_lock(void); @@ -875,4 +870,26 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ +/* Transitional pre-consolidation compatibility definitions. */ + +static inline void synchronize_rcu_bh(void) +{ + synchronize_rcu(); +} + +static inline void synchronize_rcu_bh_expedited(void) +{ + synchronize_rcu_expedited(); +} + +static inline void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) +{ + call_rcu(head, func); +} + +static inline void rcu_barrier_bh(void) +{ + rcu_barrier(); +} + #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index e66fb8bc2127..df82bada9b19 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -68,21 +68,6 @@ static inline void rcu_barrier_sched(void) rcu_barrier(); /* Only one CPU, so only one list of callbacks! */ } -static inline void rcu_barrier_bh(void) -{ - rcu_barrier(); -} - -static inline void synchronize_rcu_bh(void) -{ - synchronize_sched(); -} - -static inline void synchronize_rcu_bh_expedited(void) -{ - synchronize_sched(); -} - static inline void synchronize_rcu_expedited(void) { synchronize_sched(); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 6d30a0809300..94820156aa62 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -45,11 +45,6 @@ static inline void rcu_virt_note_context_switch(int cpu) rcu_note_context_switch(false); } -static inline void synchronize_rcu_bh(void) -{ - synchronize_rcu(); -} - void synchronize_rcu_expedited(void); static inline void synchronize_sched_expedited(void) @@ -59,19 +54,7 @@ static inline void synchronize_sched_expedited(void) void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); -/** - * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period - * - * This is a transitional API and will soon be removed, with all - * callers converted to synchronize_rcu_expedited(). - */ -static inline void synchronize_rcu_bh_expedited(void) -{ - synchronize_rcu_expedited(); -} - 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); -- cgit v1.2.3 From a8bb74acd8efe2eb934d524ae20859980975b602 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 6 Jul 2018 11:46:47 -0700 Subject: rcu: Consolidate RCU-sched update-side function definitions This commit saves a few lines by consolidating the RCU-sched function definitions at the end of include/linux/rcupdate.h. This consolidation also makes it easier to remove them all when the time comes. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 38 +++++++++++++++++++++++++++++++------- include/linux/rcutiny.h | 32 +------------------------------- include/linux/rcutree.h | 9 --------- 3 files changed, 32 insertions(+), 47 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e530f5739033..12103e1bbe67 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -48,12 +48,6 @@ #define ulong2long(a) (*(long *)(&(a))) /* Exported common interfaces */ - -#ifndef CONFIG_TINY_RCU -void synchronize_sched(void); -void call_rcu_sched(struct rcu_head *head, rcu_callback_t func); -#endif - void call_rcu(struct rcu_head *head, rcu_callback_t func); void rcu_barrier_tasks(void); void synchronize_rcu(void); @@ -170,7 +164,7 @@ void exit_tasks_rcu_finish(void); #define rcu_tasks_qs(t) do { } while (0) #define rcu_note_voluntary_context_switch(t) rcu_all_qs() #define call_rcu_tasks call_rcu_sched -#define synchronize_rcu_tasks synchronize_sched +#define synchronize_rcu_tasks synchronize_rcu static inline void exit_tasks_rcu_start(void) { } static inline void exit_tasks_rcu_finish(void) { } #endif /* #else #ifdef CONFIG_TASKS_RCU */ @@ -892,4 +886,34 @@ static inline void rcu_barrier_bh(void) rcu_barrier(); } +static inline void synchronize_sched(void) +{ + synchronize_rcu(); +} + +static inline void synchronize_sched_expedited(void) +{ + synchronize_rcu_expedited(); +} + +static inline void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) +{ + call_rcu(head, func); +} + +static inline void rcu_barrier_sched(void) +{ + rcu_barrier(); +} + +static inline unsigned long get_state_synchronize_sched(void) +{ + return get_state_synchronize_rcu(); +} + +static inline void cond_synchronize_sched(unsigned long oldstate) +{ + cond_synchronize_rcu(oldstate); +} + #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index df82bada9b19..7fa4fb9e899e 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -36,11 +36,6 @@ static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp) /* Never flag non-existent other CPUs! */ static inline bool rcu_eqs_special_set(int cpu) { return false; } -static inline void synchronize_sched(void) -{ - synchronize_rcu(); -} - static inline unsigned long get_state_synchronize_rcu(void) { return 0; @@ -51,36 +46,11 @@ static inline void cond_synchronize_rcu(unsigned long oldstate) might_sleep(); } -static inline unsigned long get_state_synchronize_sched(void) -{ - return 0; -} - -static inline void cond_synchronize_sched(unsigned long oldstate) -{ - might_sleep(); -} - extern void rcu_barrier(void); -static inline void rcu_barrier_sched(void) -{ - rcu_barrier(); /* Only one CPU, so only one list of callbacks! */ -} - static inline void synchronize_rcu_expedited(void) { - synchronize_sched(); -} - -static inline void synchronize_sched_expedited(void) -{ - synchronize_sched(); -} - -static inline void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) -{ - call_rcu(head, func); + synchronize_rcu(); } static inline void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 94820156aa62..d09a9abe9440 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -46,21 +46,12 @@ static inline void rcu_virt_note_context_switch(int cpu) } void synchronize_rcu_expedited(void); - -static inline void synchronize_sched_expedited(void) -{ - synchronize_rcu_expedited(); -} - void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func); void rcu_barrier(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); -void cond_synchronize_sched(unsigned long oldstate); void rcu_idle_enter(void); void rcu_idle_exit(void); -- cgit v1.2.3 From 2bd8b1a2afc4463cc503665e98faa5909d1ac462 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 7 Jul 2018 18:12:26 -0700 Subject: rcu: Clean up flavor-related definitions and comments in rcupdate.h Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 27 ++++++++++++--------------- 1 file changed, 12 insertions(+), 15 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 12103e1bbe67..d6d543b60a9f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -119,11 +119,10 @@ static inline void rcu_init_nohz(void) { } * RCU_NONIDLE - Indicate idle-loop code that needs RCU readers * @a: Code that RCU needs to pay attention to. * - * RCU, RCU-bh, and RCU-sched read-side critical sections are forbidden - * in the inner idle loop, that is, between the rcu_idle_enter() and - * the rcu_idle_exit() -- RCU will happily ignore any such read-side - * critical sections. However, things like powertop need tracepoints - * in the inner idle loop. + * RCU read-side critical sections are forbidden in the inner idle loop, + * that is, between the rcu_idle_enter() and the rcu_idle_exit() -- RCU + * will happily ignore any such read-side critical sections. However, + * things like powertop need tracepoints in the inner idle loop. * * This macro provides the way out: RCU_NONIDLE(do_something_with_RCU()) * will tell RCU that it needs to pay attention, invoke its argument @@ -163,7 +162,7 @@ void exit_tasks_rcu_finish(void); #else /* #ifdef CONFIG_TASKS_RCU */ #define rcu_tasks_qs(t) do { } while (0) #define rcu_note_voluntary_context_switch(t) rcu_all_qs() -#define call_rcu_tasks call_rcu_sched +#define call_rcu_tasks call_rcu #define synchronize_rcu_tasks synchronize_rcu static inline void exit_tasks_rcu_start(void) { } static inline void exit_tasks_rcu_finish(void) { } @@ -309,8 +308,8 @@ static inline void rcu_preempt_sleep_check(void) { } * Helper functions for rcu_dereference_check(), rcu_dereference_protected() * and rcu_assign_pointer(). Some of these could be folded into their * callers, but they are left separate in order to ease introduction of - * multiple flavors of pointers to match the multiple flavors of RCU - * (e.g., __rcu_sched, and __srcu), should this make sense in the future. + * multiple pointers markings to match different RCU implementations + * (e.g., __srcu), should this make sense in the future. */ #ifdef __CHECKER__ @@ -670,9 +669,8 @@ static inline void rcu_read_unlock(void) * rcu_read_lock_bh() - mark the beginning of an RCU-bh critical section * * This is equivalent of rcu_read_lock(), but also disables softirqs. - * Note that synchronize_rcu() and friends may be used for the update - * side, although synchronize_rcu_bh() is available as a wrapper in the - * short term. Longer term, the _bh update-side API will be eliminated. + * Note that anything else that disables softirqs can also serve as + * an RCU read-side critical section. * * Note that rcu_read_lock_bh() and the matching rcu_read_unlock_bh() * must occur in the same context, for example, it is illegal to invoke @@ -705,10 +703,9 @@ static inline void rcu_read_unlock_bh(void) /** * rcu_read_lock_sched() - mark the beginning of a RCU-sched critical section * - * This is equivalent of rcu_read_lock(), but to be used when updates - * are being done using call_rcu_sched() or synchronize_rcu_sched(). - * Read-side critical sections can also be introduced by anything that - * disables preemption, including local_irq_disable() and friends. + * This is equivalent of rcu_read_lock(), but disables preemption. + * Read-side critical sections can also be introduced by anything else + * that disables preemption, including local_irq_disable() and friends. * * Note that rcu_read_lock_sched() and the matching rcu_read_unlock_sched() * must occur in the same context, for example, it is illegal to invoke -- cgit v1.2.3 From aff5f0369e312b0ab0ca7a2a12dd64b7e39c7091 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 7 Jul 2018 18:12:26 -0700 Subject: rcu: Clean up flavor-related definitions and comments in rculist.h Signed-off-by: Paul E. McKenney --- include/linux/rculist.h | 32 +++++++++++++++----------------- 1 file changed, 15 insertions(+), 17 deletions(-) (limited to 'include') diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 4786c2235b98..e91ec9ddcd30 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -182,7 +182,7 @@ static inline void list_replace_rcu(struct list_head *old, * @list: the RCU-protected list to splice * @prev: points to the last element of the existing list * @next: points to the first element of the existing list - * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... + * @sync: synchronize_rcu, synchronize_rcu_expedited, ... * * The list pointed to by @prev and @next can be RCU-read traversed * concurrently with this function. @@ -240,7 +240,7 @@ static inline void __list_splice_init_rcu(struct list_head *list, * designed for stacks. * @list: the RCU-protected list to splice * @head: the place in the existing list to splice the first list into - * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... + * @sync: synchronize_rcu, synchronize_rcu_expedited, ... */ static inline void list_splice_init_rcu(struct list_head *list, struct list_head *head, @@ -255,7 +255,7 @@ static inline void list_splice_init_rcu(struct list_head *list, * list, designed for queues. * @list: the RCU-protected list to splice * @head: the place in the existing list to splice the first list into - * @sync: function to sync: synchronize_rcu(), synchronize_sched(), ... + * @sync: synchronize_rcu, synchronize_rcu_expedited, ... */ static inline void list_splice_tail_init_rcu(struct list_head *list, struct list_head *head, @@ -359,13 +359,12 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, * @type: the type of the struct this is embedded in. * @member: the name of the list_head within the struct. * - * This primitive may safely run concurrently with the _rcu list-mutation - * primitives such as list_add_rcu(), but requires some implicit RCU - * read-side guarding. One example is running within a special - * exception-time environment where preemption is disabled and where - * lockdep cannot be invoked (in which case updaters must use RCU-sched, - * as in synchronize_sched(), call_rcu_sched(), and friends). Another - * example is when items are added to the list, but never deleted. + * This primitive may safely run concurrently with the _rcu + * list-mutation primitives such as list_add_rcu(), but requires some + * implicit RCU read-side guarding. One example is running within a special + * exception-time environment where preemption is disabled and where lockdep + * cannot be invoked. Another example is when items are added to the list, + * but never deleted. */ #define list_entry_lockless(ptr, type, member) \ container_of((typeof(ptr))READ_ONCE(ptr), type, member) @@ -376,13 +375,12 @@ static inline void list_splice_tail_init_rcu(struct list_head *list, * @head: the head for your list. * @member: the name of the list_struct within the struct. * - * This primitive may safely run concurrently with the _rcu list-mutation - * primitives such as list_add_rcu(), but requires some implicit RCU - * read-side guarding. One example is running within a special - * exception-time environment where preemption is disabled and where - * lockdep cannot be invoked (in which case updaters must use RCU-sched, - * as in synchronize_sched(), call_rcu_sched(), and friends). Another - * example is when items are added to the list, but never deleted. + * This primitive may safely run concurrently with the _rcu + * list-mutation primitives such as list_add_rcu(), but requires some + * implicit RCU read-side guarding. One example is running within a special + * exception-time environment where preemption is disabled and where lockdep + * cannot be invoked. Another example is when items are added to the list, + * but never deleted. */ #define list_for_each_entry_lockless(pos, head, member) \ for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \ -- cgit v1.2.3 From df8561a0d7e4f5cb72d0aa6be43e154b2027bba6 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 7 Jul 2018 18:12:26 -0700 Subject: rcu: Clean up flavor-related definitions and comments in rcupdate_wait.h Signed-off-by: Paul E. McKenney --- include/linux/rcupdate_wait.h | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h index bc104699560e..8a16c3eb3dd0 100644 --- a/include/linux/rcupdate_wait.h +++ b/include/linux/rcupdate_wait.h @@ -33,17 +33,17 @@ do { \ /** * synchronize_rcu_mult - Wait concurrently for multiple grace periods - * @...: List of call_rcu() functions for the flavors to wait on. + * @...: List of call_rcu() functions for different grace periods to wait on * - * This macro waits concurrently for multiple flavors of RCU grace periods. - * For example, synchronize_rcu_mult(call_rcu, call_rcu_sched) would wait - * on concurrent RCU and RCU-sched grace periods. Waiting on a give SRCU + * 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() not to bother waiting for RCU - * or RCU-sched, given that anywhere synchronize_rcu_mult() can be called - * is automatically a grace period. + * 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__) -- cgit v1.2.3 From 4d232dfe1df35254298e7986c4de8c9f63f58c79 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Jul 2018 12:53:40 -0700 Subject: rcu: Remove !PREEMPT code from rcu_note_voluntary_context_switch() Because RCU-tasks exists only in PREEMPT kernels and because RCU-sched no longer exists in PREEMPT kernels, it is no longer necessary for the rcu_note_voluntary_context_switch() macro to do anything for !PREEMPT kernels. This commit therefore removes !PREEMPT-related code from this macro, namely, the rcu_all_qs(). Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index d6d543b60a9f..e4f821165d0b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -150,18 +150,14 @@ static inline void rcu_init_nohz(void) { } if (READ_ONCE((t)->rcu_tasks_holdout)) \ WRITE_ONCE((t)->rcu_tasks_holdout, false); \ } while (0) -#define rcu_note_voluntary_context_switch(t) \ - do { \ - rcu_all_qs(); \ - rcu_tasks_qs(t); \ - } while (0) +#define rcu_note_voluntary_context_switch(t) rcu_tasks_qs(t) void call_rcu_tasks(struct rcu_head *head, rcu_callback_t func); void synchronize_rcu_tasks(void); void exit_tasks_rcu_start(void); void exit_tasks_rcu_finish(void); #else /* #ifdef CONFIG_TASKS_RCU */ #define rcu_tasks_qs(t) do { } while (0) -#define rcu_note_voluntary_context_switch(t) rcu_all_qs() +#define rcu_note_voluntary_context_switch(t) do { } while (0) #define call_rcu_tasks call_rcu #define synchronize_rcu_tasks synchronize_rcu static inline void exit_tasks_rcu_start(void) { } -- cgit v1.2.3 From 395a2f097ebdddf2bfa286b6119f1b231025c2f1 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Jul 2018 14:00:14 -0700 Subject: rcu: Define rcu_all_qs() only in !PREEMPT builds Now that rcu_all_qs() is used only in !PREEMPT builds, move it to tree_plugin.h so that it is defined only in those builds. This in turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT builds, but it is simply marked __maybe_unused in order to keep it near the rest of the dyntick-idle code. Signed-off-by: Paul E. McKenney --- include/linux/rcutree.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index d09a9abe9440..7f83179177d1 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -66,7 +66,9 @@ void rcu_scheduler_starting(void); extern int rcu_scheduler_active __read_mostly; void rcu_end_inkernel_boot(void); bool rcu_is_watching(void); +#ifndef CONFIG_PREEMPT void rcu_all_qs(void); +#endif /* RCUtree hotplug events */ int rcutree_prepare_cpu(unsigned int cpu); -- cgit v1.2.3 From dd46a7882c2c2006201e053ebf5e9ad761860cc0 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Jul 2018 18:37:30 -0700 Subject: rcu: Inline _rcu_barrier() into its sole remaining caller Because rcu_barrier() is a one-line wrapper function for _rcu_barrier() and because nothing else calls _rcu_barrier(), this commit inlines _rcu_barrier() into rcu_barrier(). Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'include') diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index a8d07feff6a0..175e0bce22bd 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -705,20 +705,20 @@ TRACE_EVENT(rcu_torture_read, ); /* - * Tracepoint for _rcu_barrier() execution. The string "s" describes - * the _rcu_barrier phase: - * "Begin": _rcu_barrier() started. - * "EarlyExit": _rcu_barrier() piggybacked, thus early exit. - * "Inc1": _rcu_barrier() piggyback check counter incremented. - * "OfflineNoCB": _rcu_barrier() found callback on never-online CPU - * "OnlineNoCB": _rcu_barrier() found online no-CBs CPU. - * "OnlineQ": _rcu_barrier() found online CPU with callbacks. - * "OnlineNQ": _rcu_barrier() found online CPU, no callbacks. + * Tracepoint for rcu_barrier() execution. The string "s" describes + * the rcu_barrier phase: + * "Begin": rcu_barrier() started. + * "EarlyExit": rcu_barrier() piggybacked, thus early exit. + * "Inc1": rcu_barrier() piggyback check counter incremented. + * "OfflineNoCB": rcu_barrier() found callback on never-online CPU + * "OnlineNoCB": rcu_barrier() found online no-CBs CPU. + * "OnlineQ": rcu_barrier() found online CPU with callbacks. + * "OnlineNQ": rcu_barrier() found online CPU, no callbacks. * "IRQ": An rcu_barrier_callback() callback posted on remote CPU. * "IRQNQ": An rcu_barrier_callback() callback found no callbacks. * "CB": An rcu_barrier_callback() invoked a callback, not the last. * "LastCB": An rcu_barrier_callback() invoked the last callback. - * "Inc2": _rcu_barrier() piggyback check counter incremented. + * "Inc2": rcu_barrier() piggyback check counter incremented. * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument * is the count of remaining callbacks, and "done" is the piggybacking count. */ -- cgit v1.2.3 From 7e28c5af4ef6b539334aa5de40feca0c041c94df Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 11 Jul 2018 08:09:28 -0700 Subject: rcu: Eliminate ->rcu_qs_ctr from the rcu_dynticks structure The ->rcu_qs_ctr counter was intended to allow providing a lightweight report of a quiescent state to all RCU flavors. But now that there is only one flavor of RCU in any one running kernel, there is no point in having this feature. This commit therefore removes the ->rcu_qs_ctr field from the rcu_dynticks structure and the ->rcu_qs_ctr_snap field from the rcu_data structure. This results in the "rqc" option to the rcu_fqs trace event no longer being used, so this commit also removes the "rqc" description from the header comment. While in the neighborhood, this commit also causes the forward-progress request .rcu_need_heavy_qs be set one jiffies_till_sched_qs interval later in the grace period than the first setting of .rcu_urgent_qs. Signed-off-by: Paul E. McKenney --- include/trace/events/rcu.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 175e0bce22bd..f0c4d10e614b 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -393,9 +393,8 @@ TRACE_EVENT(rcu_quiescent_state_report, * Tracepoint for quiescent states detected by force_quiescent_state(). * These trace events include the type of RCU, the grace-period number * that was blocked by the CPU, the CPU itself, and the type of quiescent - * state, which can be "dti" for dyntick-idle mode, "kick" when kicking - * a CPU that has been in dyntick-idle mode for too long, or "rqc" if the - * CPU got a quiescent state via its rcu_qs_ctr. + * state, which can be "dti" for dyntick-idle mode or "kick" when kicking + * a CPU that has been in dyntick-idle mode for too long. */ TRACE_EVENT(rcu_fqs, -- cgit v1.2.3 From 74de6960c99d8df0d09fb29a7b014cb9c5571e2b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 24 Jul 2018 15:28:09 -0700 Subject: rcu: Provide functions for determining if call_rcu() has been invoked This commit adds rcu_head_init() and rcu_head_after_call_rcu() functions to help RCU users detect when another CPU has passed the specified rcu_head structure and function to call_rcu(). The rcu_head_init() should be invoked before making the structure visible to RCU readers, and then the rcu_head_after_call_rcu() may be invoked from within an RCU read-side critical section on an rcu_head structure that was obtained during a traversal of the data structure in question. The rcu_head_after_call_rcu() function will return true if the rcu_head structure has already been passed (with the specified function) to call_rcu(), otherwise it will return false. If rcu_head_init() has not been invoked on the rcu_head structure or if the rcu_head (AKA callback) has already been invoked, then rcu_head_after_call_rcu() will do WARN_ON_ONCE(). Reported-by: NeilBrown Signed-off-by: Paul E. McKenney [ paulmck: Apply neilb naming feedback. ] --- include/linux/rcupdate.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e4f821165d0b..4db8bcacc51a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -857,6 +857,46 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) #endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */ +/* Has the specified rcu_head structure been handed to call_rcu()? */ + +/* + * rcu_head_init - Initialize rcu_head for rcu_head_after_call_rcu() + * @rhp: The rcu_head structure to initialize. + * + * If you intend to invoke rcu_head_after_call_rcu() to test whether a + * given rcu_head structure has already been passed to call_rcu(), then + * you must also invoke this rcu_head_init() function on it just after + * allocating that structure. Calls to this function must not race with + * calls to call_rcu(), rcu_head_after_call_rcu(), or callback invocation. + */ +static inline void rcu_head_init(struct rcu_head *rhp) +{ + rhp->func = (rcu_callback_t)~0L; +} + +/* + * rcu_head_after_call_rcu - Has this rcu_head been passed to call_rcu()? + * @rhp: The rcu_head structure to test. + * @func: The function passed to call_rcu() along with @rhp. + * + * Returns @true if the @rhp has been passed to call_rcu() with @func, + * and @false otherwise. Emits a warning in any other case, including + * the case where @rhp has already been invoked after a grace period. + * Calls to this function must not race with callback invocation. One way + * to avoid such races is to enclose the call to rcu_head_after_call_rcu() + * in an RCU read-side critical section that includes a read-side fetch + * of the pointer to the structure containing @rhp. + */ +static inline bool +rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) +{ + if (READ_ONCE(rhp->func) == f) + return true; + WARN_ON_ONCE(READ_ONCE(rhp->func) != (rcu_callback_t)~0L); + return false; +} + + /* Transitional pre-consolidation compatibility definitions. */ static inline void synchronize_rcu_bh(void) -- cgit v1.2.3 From 31ab604bf3232374e6471a2df9a83c4e75538390 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 3 Aug 2018 16:15:54 -0700 Subject: rcu: Remove unused rcu_dynticks_snap() from Tiny RCU The rcu_dynticks_snap() function is defined in include/linux/rcutiny.h, but is no longer used by Tiny RCU. This commit therefore removes it. Signed-off-by: Paul E. McKenney --- include/linux/rcutiny.h | 6 ------ 1 file changed, 6 deletions(-) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 7fa4fb9e899e..f183683bdf79 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -27,12 +27,6 @@ #include -struct rcu_dynticks; -static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp) -{ - return 0; -} - /* Never flag non-existent other CPUs! */ static inline bool rcu_eqs_special_set(int cpu) { return false; } -- cgit v1.2.3 From e0fcba9ac02af5aeb1e1c3e842eab987f817c309 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 14 Aug 2018 08:45:54 -0700 Subject: srcu: Make call_srcu() available during very early boot Event tracing is moving to SRCU in order to take advantage of the fact that SRCU may be safely used from idle and even offline CPUs. However, event tracing can invoke call_srcu() very early in the boot process, even before workqueue_init_early() is invoked (let alone rcu_init()). Therefore, call_srcu()'s attempts to queue work fail miserably. This commit therefore detects this situation, and refrains from attempting to queue work before rcu_init() time, but does everything else that it would have done, and in addition, adds the srcu_struct to a global list. The rcu_init() function now invokes a new srcu_init() function, which is empty if CONFIG_SRCU=n. Otherwise, srcu_init() queues work for each srcu_struct on the list. This all happens early enough in boot that there is but a single CPU with interrupts disabled, which allows synchronization to be dispensed with. Of course, the queued work won't actually be invoked until after workqueue_init() is invoked, which happens shortly after the scheduler is up and running. This means that although call_srcu() may be invoked any time after per-CPU variables have been set up, there is still a very narrow window when synchronize_srcu() won't work, and this window extends from the time that the scheduler starts until the time that workqueue_init() returns. This can be fixed in a manner similar to the fix for synchronize_rcu_expedited() and friends, but until someone actually needs to use synchronize_srcu() during this window, this fix is added churn for no benefit. Finally, note that Tree SRCU's new srcu_init() function invokes queue_work() rather than the queue_delayed_work() function that is invoked post-boot. The reason is that queue_delayed_work() will (as you would expect) post a timer, and timers have not yet been initialized. So use of queue_work() avoids the complaints about use of uninitialized spinlocks that would otherwise result. Besides, some delay is already provide by the aforementioned fact that the queued work won't actually be invoked until after the scheduler is up and running. Requested-by: Steven Rostedt Signed-off-by: Paul E. McKenney Tested-by: Steven Rostedt (VMware) --- include/linux/srcutiny.h | 2 ++ include/linux/srcutree.h | 14 ++++++++------ 2 files changed, 10 insertions(+), 6 deletions(-) (limited to 'include') diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index f41d2fb09f87..2b5c0822e683 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -36,6 +36,7 @@ struct srcu_struct { struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ struct work_struct srcu_work; /* For driving grace periods. */ + struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -48,6 +49,7 @@ void srcu_drive_gp(struct work_struct *wp); .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ .srcu_cb_tail = &name.srcu_cb_head, \ .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ + .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ __SRCU_DEP_MAP_INIT(name) \ } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 745d4ca4dd50..9cfa4610113a 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -94,6 +94,7 @@ struct srcu_struct { /* callback for the barrier */ /* operation. */ struct delayed_work work; + struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -105,12 +106,13 @@ struct srcu_struct { #define SRCU_STATE_SCAN2 2 #define __SRCU_STRUCT_INIT(name, pcpu_name) \ - { \ - .sda = &pcpu_name, \ - .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ - .srcu_gp_seq_needed = 0 - 1, \ - __SRCU_DEP_MAP_INIT(name) \ - } +{ \ + .sda = &pcpu_name, \ + .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ + .srcu_gp_seq_needed = -1UL, \ + .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ + __SRCU_DEP_MAP_INIT(name) \ +} /* * Define and initialize a srcu struct at build time. -- cgit v1.2.3 From 4e6ea4ef56f9425cd239ffdb6be45b3aeeb347fd Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 14 Aug 2018 14:41:49 -0700 Subject: srcu: Make early-boot call_srcu() reuse workqueue lists Allocating a list_head structure that is almost never used, and, when used, is used only during early boot (rcu_init() and earlier), is a bit wasteful. This commit therefore eliminates that list_head in favor of the one in the work_struct structure. This is safe because the work_struct structure cannot be used until after rcu_init() returns. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Cc: Tejun Heo Cc: Lai Jiangshan Tested-by: Steven Rostedt (VMware) --- include/linux/srcutiny.h | 2 -- include/linux/srcutree.h | 3 +-- 2 files changed, 1 insertion(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 2b5c0822e683..f41d2fb09f87 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -36,7 +36,6 @@ struct srcu_struct { struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ struct work_struct srcu_work; /* For driving grace periods. */ - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -49,7 +48,6 @@ void srcu_drive_gp(struct work_struct *wp); .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ .srcu_cb_tail = &name.srcu_cb_head, \ .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ __SRCU_DEP_MAP_INIT(name) \ } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 9cfa4610113a..0ae91b3a7406 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -94,7 +94,6 @@ struct srcu_struct { /* callback for the barrier */ /* operation. */ struct delayed_work work; - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -110,7 +109,7 @@ struct srcu_struct { .sda = &pcpu_name, \ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ .srcu_gp_seq_needed = -1UL, \ - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ + .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ __SRCU_DEP_MAP_INIT(name) \ } -- cgit v1.2.3