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 <paulmck@linux.vnet.ibm.com>
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index a033d8b..36ea3ba 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -348,8 +348,8 @@
*/
#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)