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Subject[PATCH 02/10] nohz: Kick full dynticks timer targets with an empty IPI
Date
While we enqueue a new timer on a dynticks target, we must send it an
IPI so that it reschedules the next tick accordingly.

Now all we need for that is to run irq_exit() on the target. Hence
an empty IRQ is way enough. We don't need to run tick_nohz_full_check()
and all the overhead that comes with the several cmpxchg() necessary for
irq work list and state progress.

So lets use a void irq work instead.

Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f3063c..f3e48b8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -693,7 +693,7 @@ static bool wake_up_full_nohz_cpu(int cpu)
if (tick_nohz_full_cpu(cpu)) {
if (cpu != smp_processor_id() ||
tick_nohz_tick_stopped())
- tick_nohz_full_kick_cpu(cpu);
+ irq_work_void_on(cpu);
return true;
}

--
1.8.3.1


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