[PATCH 2/9] nohz: Implement wide kick on top of irq work

[Frederic Weisbecker]

It simplifies it and allows wide kick to be performed, even when IRQs
are disabled, without an asynchronous level in the middle.

This comes at a cost of some more overhead on features like perf and
posix cpu timers slow-paths, which is probably not much important
for nohz full users.

Requested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reviewed-by: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
---
 kernel/time/tick-sched.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 9d7a053..f6a980f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -232,24 +232,20 @@ void tick_nohz_full_kick_cpu(int cpu)
 	irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
 }
 
-static void nohz_full_kick_ipi(void *info)
-{
-	/* Empty, the tick restart happens on tick_nohz_irq_exit() */
-}
-
 /*
  * Kick all full dynticks CPUs in order to force these to re-evaluate
  * their dependency on the tick and restart it if necessary.
  */
 void tick_nohz_full_kick_all(void)
 {
+	int cpu;
+
 	if (!tick_nohz_full_running)
 		return;
 
 	preempt_disable();
-	smp_call_function_many(tick_nohz_full_mask,
-			       nohz_full_kick_ipi, NULL, false);
-	tick_nohz_full_kick();
+	for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
+		tick_nohz_full_kick_cpu(cpu);
 	preempt_enable();
 }
 
-- 
2.7.0