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Date: Fri, 12 Dec 2014 17:17:03 +0530 From: Preeti U Murthy <preeti@...ux.vnet.ibm.com> To: Santosh Shukla <santosh.shukla@...aro.org> CC: Viresh Kumar <viresh.kumar@...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 12/11/2014 10:26 AM, Santosh Shukla wrote: > On 11 December 2014 at 10:14, Preeti U Murthy <preeti@...ux.vnet.ibm.com> wrote: >> On 12/10/2014 06:22 PM, Viresh Kumar wrote: >>> On 10 December 2014 at 18:03, Preeti U Murthy <preeti@...ux.vnet.ibm.com> wrote: >>> >>>> Right. We get an interrupt when nobody had asked for it to be delivered >>>> or had asked for it to be delivered and later canceled the request. It >>>> is most often in the latter situation, that there can be race >>>> conditions. If these race conditions are not taken care of, they can >>>> result in spurious interrupts. >>> >>> But the delta time will be very small then, right ? >> >> 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 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. >> > > I verified this case before reporting; In my case tick_sched_timer do > get cancelled before expire duration but then clk_evt_device get > reprogrammed for next time node in list. __remove_hrtimer() takes > care of that. Right. The scenario I described happens in the Low Resolution Mode. You are right, this does not happen in the High Resolution Mode. Regards Preeti U Murthy -- 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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