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| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-07-01 11:26:57 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2014-09-07 16:27:20 -0700 |
| commit | bde6c3aa993066acb0d6ce32ecabe03b9d5df92d (patch) | |
| tree | 09ec78a9cfa751ce36288c32c4e5112f34af8582 /include/linux/rcupdate.h | |
| parent | 8315f42295d2667a7f942f154b73a86fd7cb2227 (diff) | |
| download | lwn-bde6c3aa993066acb0d6ce32ecabe03b9d5df92d.tar.gz lwn-bde6c3aa993066acb0d6ce32ecabe03b9d5df92d.zip | |
rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops
RCU-tasks requires the occasional voluntary context switch
from CPU-bound in-kernel tasks. In some cases, this requires
instrumenting cond_resched(). However, there is some reluctance
to countenance unconditionally instrumenting cond_resched() (see
http://lwn.net/Articles/603252/), so this commit creates a separate
cond_resched_rcu_qs() that may be used in place of cond_resched() in
locations prone to long-duration in-kernel looping.
This commit currently instruments only RCU-tasks. Future possibilities
include also instrumenting RCU, RCU-bh, and RCU-sched in order to reduce
IPI usage.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/rcupdate.h')
| -rw-r--r-- | include/linux/rcupdate.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3432063f4c87..473350462d04 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -330,6 +330,19 @@ static inline void rcu_user_hooks_switch(struct task_struct *prev, #define rcu_note_voluntary_context_switch(t) do { } while (0) #endif /* #else #ifdef CONFIG_TASKS_RCU */ +/** + * cond_resched_rcu_qs - Report potential quiescent states to RCU + * + * This macro resembles cond_resched(), except that it is defined to + * report potential quiescent states to RCU-tasks even if the cond_resched() + * machinery were to be shut off, as some advocate for PREEMPT kernels. + */ +#define cond_resched_rcu_qs() \ +do { \ + rcu_note_voluntary_context_switch(current); \ + cond_resched(); \ +} while (0) + #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) bool __rcu_is_watching(void); #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */ |