linux-kernel - [PATCH 4.18 085/145] sched: idle: Avoid retaining the tick when it has been stopped

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Date:   Fri,  7 Sep 2018 23:09:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.18 085/145] sched: idle: Avoid retaining the tick when it has been stopped

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

commit 7059b36636beab57c3c43c62104483e5449bee95 upstream.

If the tick has been stopped already, but the governor has not asked to
stop it (which it can do sometimes), the idle loop should invoke
tick_nohz_idle_stop_tick(), to let tick_nohz_stop_tick() take care
of this case properly.

Fixes: 554c8aa8ecad (sched: idle: Select idle state before stopping the tick)
Cc: 4.17+ <stable@...r.kernel.org> # 4.17+
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/idle.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -190,7 +190,7 @@ static void cpuidle_idle_call(void)
 		 */
 		next_state = cpuidle_select(drv, dev, &stop_tick);

-		if (stop_tick)
+		if (stop_tick || tick_nohz_tick_stopped())
 			tick_nohz_idle_stop_tick();
 		else
 			tick_nohz_idle_retain_tick();