From 28f6569ab7d036cd4ee94c26bb76dc1b3f3fc056 Mon Sep 17 00:00:00 2001 From: Pranith Kumar Date: Mon, 22 Sep 2014 14:00:48 -0400 Subject: rcu: Remove redundant TREE_PREEMPT_RCU config option PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after TINY_PREEMPT_RCU has been removed. This patch removes TREE_PREEMPT_RCU and uses PREEMPT_RCU config option in its place. Signed-off-by: Pranith Kumar Signed-off-by: Paul E. McKenney --- include/linux/init_task.h | 2 +- include/linux/rcupdate.h | 6 +++--- include/linux/sched.h | 4 ++-- include/trace/events/rcu.h | 4 ++-- 4 files changed, 8 insertions(+), 8 deletions(-) (limited to 'include') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 77fc43f8fb72..d996aef8044f 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -102,7 +102,7 @@ extern struct group_info init_groups; #define INIT_IDS #endif -#ifdef CONFIG_TREE_PREEMPT_RCU +#ifdef CONFIG_PREEMPT_RCU #define INIT_TASK_RCU_TREE_PREEMPT() \ .rcu_blocked_node = NULL, #else diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a4a819ffb2d1..295bb4595de6 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -57,7 +57,7 @@ enum rcutorture_type { INVALID_RCU_FLAVOR }; -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, unsigned long *gpnum, unsigned long *completed); void rcutorture_record_test_transition(void); @@ -365,7 +365,7 @@ typedef void call_rcu_func_t(struct rcu_head *head, void (*func)(struct rcu_head *head)); void wait_rcu_gp(call_rcu_func_t crf); -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) #include #elif defined(CONFIG_TINY_RCU) #include @@ -852,7 +852,7 @@ static inline void rcu_preempt_sleep_check(void) * * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU), * it is illegal to block while in an RCU read-side critical section. - * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT + * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT * kernel builds, RCU read-side critical sections may be preempted, * but explicit blocking is illegal. Finally, in preemptible RCU * implementations in real-time (with -rt patchset) kernel builds, RCU diff --git a/include/linux/sched.h b/include/linux/sched.h index 5e344bbe63ec..706a9f744909 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1278,9 +1278,9 @@ struct task_struct { union rcu_special rcu_read_unlock_special; struct list_head rcu_node_entry; #endif /* #ifdef CONFIG_PREEMPT_RCU */ -#ifdef CONFIG_TREE_PREEMPT_RCU +#ifdef CONFIG_PREEMPT_RCU struct rcu_node *rcu_blocked_node; -#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ +#endif /* #ifdef CONFIG_PREEMPT_RCU */ #ifdef CONFIG_TASKS_RCU unsigned long rcu_tasks_nvcsw; bool rcu_tasks_holdout; diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index e335e7d8c6c2..c78e88ce5ea3 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -36,7 +36,7 @@ TRACE_EVENT(rcu_utilization, #ifdef CONFIG_RCU_TRACE -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) /* * Tracepoint for grace-period events. Takes a string identifying the @@ -345,7 +345,7 @@ TRACE_EVENT(rcu_fqs, __entry->cpu, __entry->qsevent) ); -#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) */ +#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) */ /* * Tracepoint for dyntick-idle entry/exit events. These take a string -- cgit From c3377c2da6e594504c900d5ef72374c109e4ca99 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 21 Oct 2014 07:53:02 -0700 Subject: rcu: Remove "cpu" argument to rcu_check_callbacks() The "cpu" argument was kept around on the off-chance that RCU might offload scheduler-clock interrupts. However, this offload approach has been replaced by NO_HZ_FULL, which offloads -all- RCU processing from qualifying CPUs. It is therefore time to remove the "cpu" argument to rcu_check_callbacks(), which this commit does. Signed-off-by: Paul E. McKenney Reviewed-by: Pranith Kumar --- include/linux/rcupdate.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a4a819ffb2d1..b4ad275d90d0 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -260,7 +260,7 @@ static inline int rcu_preempt_depth(void) void rcu_init(void); void rcu_sched_qs(void); void rcu_bh_qs(void); -void rcu_check_callbacks(int cpu, int user); +void rcu_check_callbacks(int user); struct notifier_block; void rcu_idle_enter(void); void rcu_idle_exit(void); -- cgit From 38200cf24702e5d79ce6c8f4c62036c41845c62d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 21 Oct 2014 12:50:04 -0700 Subject: rcu: Remove "cpu" argument to rcu_note_context_switch() The "cpu" argument to rcu_note_context_switch() is always the current CPU, so drop it. This in turn allows the "cpu" argument to rcu_preempt_note_context_switch() to be removed, which allows the sole use of "cpu" in both functions to be replaced with a this_cpu_ptr(). Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: Paul E. McKenney Reviewed-by: Pranith Kumar --- include/linux/rcutiny.h | 2 +- include/linux/rcutree.h | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 38cc5b1e252d..0e5366200154 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -78,7 +78,7 @@ static inline void kfree_call_rcu(struct rcu_head *head, call_rcu(head, func); } -static inline void rcu_note_context_switch(int cpu) +static inline void rcu_note_context_switch(void) { rcu_sched_qs(); } diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 3e2f5d432743..7b5484db1857 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -30,7 +30,7 @@ #ifndef __LINUX_RCUTREE_H #define __LINUX_RCUTREE_H -void rcu_note_context_switch(int cpu); +void rcu_note_context_switch(void); #ifndef CONFIG_RCU_NOCB_CPU_ALL int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies); #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ @@ -43,7 +43,7 @@ void rcu_cpu_stall_reset(void); */ static inline void rcu_virt_note_context_switch(int cpu) { - rcu_note_context_switch(cpu); + rcu_note_context_switch(); } void synchronize_rcu_bh(void); -- cgit From aa6da5140b784ece799f670bf532096f67aa7785 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 21 Oct 2014 13:23:08 -0700 Subject: rcu: Remove "cpu" argument to rcu_needs_cpu() The "cpu" argument to rcu_needs_cpu() is always the current CPU, so drop it. This in turn allows the "cpu" argument to rcu_cpu_has_callbacks() to be removed, which allows the uses of "cpu" in both functions to be replaced with a this_cpu_ptr(). Again, the anticipated cross-CPU uses of these functions has been replaced by NO_HZ_FULL. Signed-off-by: Paul E. McKenney Reviewed-by: Pranith Kumar --- include/linux/rcupdate.h | 2 +- include/linux/rcutree.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index b4ad275d90d0..4eb810832b19 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1103,7 +1103,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) __kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head)) #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL) -static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies) +static inline int rcu_needs_cpu(unsigned long *delta_jiffies) { *delta_jiffies = ULONG_MAX; return 0; diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 7b5484db1857..52953790dcca 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -32,7 +32,7 @@ void rcu_note_context_switch(void); #ifndef CONFIG_RCU_NOCB_CPU_ALL -int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies); +int rcu_needs_cpu(unsigned long *delta_jiffies); #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ void rcu_cpu_stall_reset(void); -- cgit From 1a6c9b2675460718f819def9a272cca35575eeb7 Mon Sep 17 00:00:00 2001 From: Pranith Kumar Date: Thu, 25 Sep 2014 14:03:34 -0400 Subject: rcu: Add sparse check for RCU_INIT_POINTER() Add a sparse check when RCU_INIT_POINTER() is used to assign a non __rcu annotated pointer. Signed-off-by: Pranith Kumar Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a4a819ffb2d1..a033d8b55773 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1047,6 +1047,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void) */ #define RCU_INIT_POINTER(p, v) \ do { \ + rcu_dereference_sparse(p, __rcu); \ p = RCU_INITIALIZER(v); \ } while (0) -- cgit From b6331ae8afe4118884c4b6e14a213758d88422b2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 4 Oct 2014 03:43:41 -0700 Subject: rcu: Optimize cond_resched_rcu_qs() The current implementation of cond_resched_rcu_qs() can invoke rcu_note_voluntary_context_switch() twice in the should_resched() case, once via the call to __schedule() and once directly. However, as noted by Joe Lawrence in a patch to the team subsystem, cond_resched() returns an indication as to whether or not the call to __schedule() actually happened. This commit therefore changes cond_resched_rcu_qs() so as to invoke rcu_note_voluntary_context_switch() only when __schedule() was not called. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a033d8b55773..36ea3ba5c516 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -348,8 +348,8 @@ extern struct srcu_struct tasks_rcu_exit_srcu; */ #define cond_resched_rcu_qs() \ do { \ - rcu_note_voluntary_context_switch(current); \ - cond_resched(); \ + if (!cond_resched()) \ + rcu_note_voluntary_context_switch(current); \ } while (0) #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) -- cgit From ce36f2f3eb6613a73bc6f3a5256bde7dd3f95710 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sun, 28 Sep 2014 23:44:21 +0200 Subject: rcu: More info about potential deadlocks with rcu_read_unlock() The comment above rcu_read_unlock() explains the potential deadlock if the caller holds one of the locks taken by rt_mutex_unlock() paths, but it is not clear from this documentation that any lock which can be taken from interrupt can lead to deadlock as well and we need to take rt_mutex_lock() into account too. The problem is that rt_mutex_lock() takes wait_lock without disabling irqs, and thus an interrupt taking some LOCK can obviously race with rcu_read_unlock_special() called with the same LOCK held. Signed-off-by: Oleg Nesterov Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 36ea3ba5c516..ae6942a84a0d 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -887,7 +887,9 @@ static inline void rcu_read_lock(void) * Unfortunately, this function acquires the scheduler's runqueue and * priority-inheritance spinlocks. This means that deadlock could result * if the caller of rcu_read_unlock() already holds one of these locks or - * any lock that is ever acquired while holding them. + * any lock that is ever acquired while holding them; or any lock which + * can be taken from interrupt context because rcu_boost()->rt_mutex_lock() + * does not disable irqs while taking ->wait_lock. * * That said, RCU readers are never priority boosted unless they were * preempted. Therefore, one way to avoid deadlock is to make sure -- cgit