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Date: Sat, 19 Nov 2011 12:08:37 +0800 From: Yong Zhang <yong.zhang0@...il.com> To: Jeff Ohlstein <johlstei@...eaurora.org> Cc: Thomas Gleixner <tglx@...utronix.de>, linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] hrtimer: Fix extra wakeups from __remove_hrtimer() On Fri, Nov 18, 2011 at 03:47:10PM -0800, Jeff Ohlstein wrote: > __remove_hrtimer() attempts to reprogram the clockevent device when > the timer being removed is the next to expire. However, > __remove_hrtimer() reprograms the clockevent *before* removing the > timer from the timerqueue and thus when hrtimer_force_reprogram() > finds the next timer to expire it finds the timer we're trying to > remove. > > This is especially noticeable when the system switches to NOHz mode > and the system tick is removed. The timer tick is removed from the > system but the clockevent is programmed to wakeup in another HZ > anyway. Reduced one needless call of hrtimer_interrupt() indeed. > > Silence the extra wakeup by removing the timer from the timerqueue > before calling hrtimer_force_reprogram() so that we actually program > the clockevent for the next timer to expire. > > This was broken by 998adc3 "hrtimers: Convert hrtimers to use > timerlist infrastructure". The issue also exists before 998adc3. Apart from that. Reviewed-by: Yong Zhang <yong.zhang0@...il.com> > > Signed-off-by: Jeff Ohlstein <johlstei@...eaurora.org> > --- > kernel/hrtimer.c | 6 ++++-- > 1 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c > index 422e567..ae34bf5 100644 > --- a/kernel/hrtimer.c > +++ b/kernel/hrtimer.c > @@ -885,10 +885,13 @@ static void __remove_hrtimer(struct hrtimer *timer, > struct hrtimer_clock_base *base, > unsigned long newstate, int reprogram) > { > + struct timerqueue_node *next_timer; > if (!(timer->state & HRTIMER_STATE_ENQUEUED)) > goto out; > > - if (&timer->node == timerqueue_getnext(&base->active)) { > + next_timer = timerqueue_getnext(&base->active); > + timerqueue_del(&base->active, &timer->node); > + if (&timer->node == next_timer) { > #ifdef CONFIG_HIGH_RES_TIMERS > /* Reprogram the clock event device. if enabled */ > if (reprogram && hrtimer_hres_active()) { > @@ -901,7 +904,6 @@ static void __remove_hrtimer(struct hrtimer *timer, > } > #endif > } > - timerqueue_del(&base->active, &timer->node); > if (!timerqueue_getnext(&base->active)) > base->cpu_base->active_bases &= ~(1 << base->index); > out: > -- > Sent by an employee of the Qualcomm Innovation Center, Inc. > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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