tick/nohz: Set the correct expiry when switching to nohz/lowres mode

commit 1ca8ec532fc2d986f1f4a319857bb18e0c9739b4 upstream.

commit 0ff53d096422 sets the next tick interrupt to the last jiffies update,
i.e. in the past, because the forward operation is invoked before the set
operation. There is no resulting damage (yet), but we get an extra pointless
tick interrupt.

Revert the order so we get the next tick interrupt in the future.

Fixes: commit 0ff53d096422 "tick: sched: Force tick interrupt and get rid of softirq magic"
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: http://lkml.kernel.org/r/1453893967-3458-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7c7ec45159834a1b25576fbed037c9951f3c076f..22c57e191a234f1f5a6cde4121eb30d7cb6ec9a4 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -977,9 +977,9 @@ static void tick_nohz_switch_to_nohz(void)
        /* Get the next period */
        next = tick_init_jiffy_update();
 
-       hrtimer_forward_now(&ts->sched_timer, tick_period);
        hrtimer_set_expires(&ts->sched_timer, next);
-       tick_program_event(next, 1);
+       hrtimer_forward_now(&ts->sched_timer, tick_period);
+       tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
        tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
 }