linux-kernel - Re: clockevents_shutdown vs pending interrupt

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Date:	Tue, 23 Jun 2015 12:15:52 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andriy Gapon <avg@...eBSD.org>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: clockevents_shutdown vs pending interrupt

On Tue, 23 Jun 2015, Andriy Gapon wrote:
> Pardon if I am asking something obvious or silly...
> 
> tick_check_new_device() has the following code:
> 
>         if (tick_is_broadcast_device(curdev)) {
>                 clockevents_shutdown(curdev);
>                 curdev = NULL;
>         }
> 
> and
> 
> void clockevents_shutdown(struct clock_event_device *dev)
> {
>         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
>         dev->next_event.tv64 = KTIME_MAX;
> }
> 
> This is all done while interrupts are disabled on the current CPU.
> But what if there is already a pending interrupt from the current source?
> Is it possible that the timer interrupt would be processed by the device that
> was put in the shutdown mode?
> 
> Some context: I am experiencing exactly the same symptoms as described here
> http://thread.gmane.org/gmane.linux.kernel/1483297.  But I run a kernel where
> that bug is fixed.  And my problem happens in a VM, so it's possible that there
> are timing issues which are very unlikely on real hardware.

Can you provide a full dmesg please?

Thanks,

	tglx

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