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| author |   Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-09-06 17:39:49 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2013-09-25 06:44:41 -0700 |
| commit | cc6783f788d8fe8b23ec6fc2762f5e8c9a418eee (patch) | |
| tree | dfecd009a80c422393c2c6130d9a38ec7329e851 /include/linux | |
| parent | rcu: Throttle invoke_rcu_core() invocations due to non-lazy callbacks (diff) | |
| download | linux-dev-cc6783f788d8fe8b23ec6fc2762f5e8c9a418eee.tar.xz linux-dev-cc6783f788d8fe8b23ec6fc2762f5e8c9a418eee.zip | |
rcu: Is it safe to enter an RCU read-side critical section?
There is currently no way for kernel code to determine whether it
is safe to enter an RCU read-side critical section, in other words,
whether or not RCU is paying attention to the currently running CPU.
Given the large and increasing quantity of code shared by the idle loop
and non-idle code, the this shortcoming is becoming increasingly painful.
This commit therefore adds __rcu_is_watching(), which returns true if
it is safe to enter an RCU read-side critical section on the currently
running CPU. This function is quite fast, using only a __this_cpu_read().
However, the caller must disable preemption.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Diffstat (limited to 'include/linux')
| -rw-r--r-- | include/linux/rcupdate.h | 8 | ||||
| -rw-r--r-- | include/linux/rcutiny.h | 9 | ||||
| -rw-r--r-- | include/linux/rcutree.h | 2 |
3 files changed, 15 insertions, 4 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index f1f1bc39346b..a53a21a2808c 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -261,6 +261,10 @@ static inline void rcu_user_hooks_switch(struct task_struct *prev, rcu_irq_exit(); \ } while (0) +#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) +extern int rcu_is_cpu_idle(void); +#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ + /* * Infrastructure to implement the synchronize_() primitives in * TREE_RCU and rcu_barrier_() primitives in TINY_RCU. @@ -297,10 +301,6 @@ static inline void destroy_rcu_head_on_stack(struct rcu_head *head) } #endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */ -#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) -extern int rcu_is_cpu_idle(void); -#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SMP) */ - #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) bool rcu_lockdep_current_cpu_online(void); #else /* #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PROVE_RCU) */ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index e31005ee339e..bee665964878 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -132,4 +132,13 @@ static inline void rcu_scheduler_starting(void) } #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ +#ifdef CONFIG_RCU_TRACE + +static inline bool __rcu_is_watching(void) +{ + return !rcu_is_cpu_idle(); +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ + #endif /* __LINUX_RCUTINY_H */ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 226169d1bd2b..293613dfd2a5 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -90,4 +90,6 @@ extern void exit_rcu(void); extern void rcu_scheduler_starting(void); extern int rcu_scheduler_active __read_mostly; +extern bool __rcu_is_watching(void); + #endif /* __LINUX_RCUTREE_H */ |