From: Paul E. McKenney Date: Sat, 4 Oct 2014 10:43:41 +0000 (-0700) Subject: rcu: Optimize cond_resched_rcu_qs() X-Git-Tag: firefly_0821_release~176^2~2760^2^2^4~2 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=b6331ae8afe4118884c4b6e14a213758d88422b2;p=firefly-linux-kernel-4.4.55.git 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 --- 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)