linux-kernel - Re: [PATCH 1/2] hrtimer: update '->active_bases' before calling hrtimer_force

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Message-ID: <CAKohponHP9yhjrRt_igvA9554DwU7cUUR=VC4cLOapcgXBrZxA@mail.gmail.com>
Date:	Thu, 2 Apr 2015 19:53:59 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] hrtimer: update '->active_bases' before calling hrtimer_force_reprogram()

On 2 April 2015 at 19:46, Peter Zijlstra <peterz@...radead.org> wrote:
> So then I'm not seeing how its a bug. Sure __hrtimer_get_next_event()
> will iterate all the bases again, and it will not skip the just empty
> one. But I don't see how that is anything but an inefficiency. By virtue
> of the base being empty it cannot find an event there, so its a
> pointless check.
>
> What am I missing?

Hmm. It was a bug for me because I was doing this unconditionally:
timer = container_of(timerqueue_getnext(&base->active),
+                                    struct hrtimer, node);

And this will give a container-of over NULL, as timerqueue_getnext() can
return NULL..

And so it will crash in my case.

But I understand your point, its inefficiency only :(
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