linux-kernel - RE: [PATCH v3] hrtimers: calculate expires

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Message-ID: <alpine.DEB.2.11.1501221144210.5526@nanos>
Date:	Thu, 22 Jan 2015 11:45:16 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	vigneshr@...eaurora.org
cc:	stfomichev@...dex-team.ru, linux-kernel@...r.kernel.org,
	john.stultz@...aro.org, viresh.kumar@...aro.org,
	fweisbec@...il.com, mingo@...nel.org, cl@...ux.com,
	psodagud@...eaurora.org, sboyd@...eaurora.org
Subject: RE: [PATCH v3] hrtimers: calculate expires_next after all timers
 are executed

On Wed, 21 Jan 2015, vigneshr@...eaurora.org wrote:

> Hi Thomas,
> 
> In this patch, we are only setting the flag
> cpu_base->in_hrtirq = 1; in hrtimer_interrupt() and not resetting it.
> 
> 
> > @@ -1251,9 +1251,9 @@ void hrtimer_interrupt(struct clock_even
> > dev->next_event.tv64 = KTIME_MAX;
> >
> > raw_spin_lock(&cpu_base->lock);
> > + cpu_base->in_hrtirq = 1;
> 
> Since this is the case, after the hrtimer_interrupt routine completes and
> new timer is started and say it happens to be leftmost,
> we don't allow hrtimer_reprogram() since we bail out given that
> cpu_base->in_hrtirq=1 :
> 
> timer irq comes
> --->hrtimer_interrupt()
> ---->cpu_base->in_hrtirq flag is set
> ------>Interrupt is serviced
> 
> After sometime
> 
> -->__hrtimer_start_range_ns()
> --->happens to be leftmost hence call hrtimer_enqueue_reprogram()
> ----->hrtimer_reprogram()
> ------->bail out since cpu_base->in_hrtirq flag is stil set
> 
> At the end of hrtimer interrupt routine, i think we should also clear this
> flag.

Bah, yes. I moved it around several times and then dropped it.
 
Thanks for spotting it!

       tglx
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