From: Frederic Weisbecker If we were running adaptive tickless but then we schedule out and enter the idle task, we don't need to restart the tick because tick_nohz_idle_enter() is going to be called right away. The only thing we need to do is to save the jiffies such that when we later restart the tick we can account the CPU time spent while idle was tickless. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Avi Kivity Cc: Chris Metcalf Cc: Christoph Lameter Cc: Daniel Lezcano Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Max Krasnyansky Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Steven Rostedt Cc: Sven-Thorsten Dietrich Cc: Thomas Gleixner --- kernel/time/tick-sched.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 2627663..16267ee 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -1036,14 +1036,18 @@ void tick_nohz_pre_schedule(void) void tick_nohz_post_schedule(void) { struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); + unsigned long flags; - /* - * No need to disable irqs here. The worst that can happen - * is an irq that comes and restart the tick before us. - * tick_nohz_restart_sched_tick() is irq safe. - */ - if (ts->tick_stopped) - tick_nohz_restart_sched_tick(); + local_irq_save(flags); + if (ts->tick_stopped) { + if (is_idle_task(current)) { + ts->saved_jiffies = jiffies; + ts->saved_jiffies_whence = JIFFIES_SAVED_IDLE; + } else { + tick_nohz_restart_sched_tick(); + } + } + local_irq_restore(flags); } void tick_nohz_flush_current_times(bool restart_tick) -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/