linux-kernel - Re: [Query] Spurious interrupts from clockevent device on X86 Ivybridge

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Message-ID: <CAKohpo=VOKF3wgvpp4Ut4jY4PgkD49+tGsU0EMFbU_LXw_d+aw@mail.gmail.com>
Date:	Thu, 11 Dec 2014 10:48:50 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Cc:	Santosh Shukla <santosh.shukla@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Kevin Hilman <khilman@...aro.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [Query] Spurious interrupts from clockevent device on X86 Ivybridge

On 11 December 2014 at 10:14, Preeti U Murthy <preeti@...ux.vnet.ibm.com> wrote:
> I was talking of the case where we get an interrupt from the clockevent
> device but dont find the hrtimer to service and not really of an anomaly
> in timekeeping.

For sure that's a problem then and its obviously spurious unless we wanted
it to behave that way.

>    For instance one of the issues that we had seen earlier wherein we
> cancel the tick-sched-timer before going tickless, but since we had
> programmed the clock event device to fire, we get a spurious interrupt.

Yeah and so we need something like ONESHOT_STOPPED there..

I thought you are also talking about some *possible* races which might
occur between cancelling a timer and hrtimer_interrupt() getting called.
Don't know if such a race is possible though.
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