Messages in this thread Patch in this message | | | Date | Tue, 22 Apr 2014 09:35:41 +0530 | From | viresh kumar <> | Subject | Re: [PATCH V2 14/19] tick-sched: add comment about 'idle_active' in tick_nohz_idle_exit() |
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On Tuesday 22 April 2014 04:50 AM, Frederic Weisbecker wrote: > It's still over-detailed. Much of the above is easily deduced after common review. OTOH > I proposed to summarize there: https://lkml.org/lkml/2014/4/11/334 > The below disambiguates it a bit further.
Hmm.. Something broke for sure in my repo. I do remember updating this patch with your comments and something went wrong while playing with patches.
Sorry for that. Fixed my repo now.
> Now it's eventually getting as big as your comment ;-) > > > /* > * ts->idle_active drives the idle time which typically elapses in the idle loop > * but breaks on IRQs interrupting idle loop. > * > * Hence ts->idle_active can be 1 here if we exit the idle loop without the help of > * an IRQ. OTOH it can be 0 on idle exit if a wake up IPI pulled the CPU out of > * the idle loop. Since we know that we'll be exiting the idle task after the wake > * up IPI, all the pending idle sleep time is flushed on irq entry and no more is > * accounted further thanks to the need_resched() check on irq_exit(). > */
@Thomas: Please consider this patch instead:
Author: Viresh Kumar <viresh.kumar@linaro.org> Date: Mon Apr 21 15:25:10 2014 +0530
tick-sched: add comment about 'idle_active' in tick_nohz_idle_exit()
The sequence of calls for dynticks CPUs is a bit confusing. Add a comment in tick_nohz_idle_exit() to mention it clearly. All information required is in commit and this conversation with Frederic.
https://lkml.org/lkml/2014/4/10/355
Suggested-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- kernel/time/tick-sched.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 71f64ee..b2f024f 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -922,6 +922,17 @@ void tick_nohz_idle_exit(void)
ts->inidle = 0;
+ /* + * ts->idle_active drives the idle time which typically elapses in the + * idle loop but breaks on IRQs interrupting idle loop. + * + * Hence ts->idle_active can be 1 here if we exit the idle loop without + * the help of an IRQ. OTOH it can be 0 on idle exit if a wake up IPI + * pulled the CPU out of the idle loop. Since we know that we'll be + * exiting the idle task after the wake up IPI, all the pending idle + * sleep time is flushed on irq entry and no more is accounted further + * thanks to the need_resched() check on irq_exit(). + */ if (ts->idle_active || ts->tick_stopped) now = ktime_get();
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