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authorFrederic Weisbecker <frederic@kernel.org>2021-05-27 13:34:41 +0200
committerPeter Zijlstra <peterz@infradead.org>2021-05-31 10:14:49 +0200
commitf268c3737ecaefcfeecfb4cb5e44958a8976f067 (patch)
tree895c3ffc8d716b3d00851b569eb183f73a95d9fc /include/linux/tick.h
parent02da26ad5ed6ea8680e5d01f20661439611ed776 (diff)
tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed
Checking for and processing RCU-nocb deferred wakeup upon user/guest entry is only relevant when nohz_full runs on the local CPU, otherwise the periodic tick should take care of it. Make sure we don't needlessly pollute these fast-paths as a -3% performance regression on a will-it-scale.per_process_ops has been reported so far. Fixes: 47b8ff194c1f (entry: Explicitly flush pending rcuog wakeup before last rescheduling point) Fixes: 4ae7dc97f726 (entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point) Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210527113441.465489-1-frederic@kernel.org
Diffstat (limited to 'include/linux/tick.h')
-rw-r--r--include/linux/tick.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 7340613c7eff..1a0ff88fa107 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -11,6 +11,7 @@
#include <linux/context_tracking_state.h>
#include <linux/cpumask.h>
#include <linux/sched.h>
+#include <linux/rcupdate.h>
#ifdef CONFIG_GENERIC_CLOCKEVENTS
extern void __init tick_init(void);
@@ -300,4 +301,10 @@ static inline void tick_nohz_task_switch(void)
__tick_nohz_task_switch();
}
+static inline void tick_nohz_user_enter_prepare(void)
+{
+ if (tick_nohz_full_cpu(smp_processor_id()))
+ rcu_nocb_flush_deferred_wakeup();
+}
+
#endif