linux-kernel - Re: [PATCH] rtc: interface: ignore exprired timers one enqueing new timers

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Date:	Thu, 19 May 2016 18:38:22 +0200
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Colin King <colin.king@...onical.com>
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rtc: interface: ignore exprired timers one enqueing new
 timers

Hi Colin,

On 16/05/2016 at 17:22:54 +0100, Colin King wrote :
> From: Colin Ian King <colin.king@...onical.com>
> 
> This patch fixes a RTC wakealarm issue, namely, the event fires during
> hibernate and is not cleared from the list, causing hwclock to block.
> 
> The current enqueuing does not trigger an alarm if any expired timers
> already exist on the timerqueue. This can occur when a RTC wake alarm
> is used to wake a machine out of hibernate and the resumed state has
> old expired timers that have not been removed from the timer queue.
> This fix skips over any expired timers and triggers an alarm if there
> are no pending timers on the timerqueue. Note that the skipped expired
> timer will get repead later on, so there is no need to clean it up
> immediately.
> 
> The issue can be reproduced by putting a machine into hibernate and
> waking it with the RTC wakealarm.  Running the example RTC test program
> from tools/testing/selftests/timers/rtctest.c after the hibernate will
> block indefinitely.  With the fix, it no longer blocks after the
> hibernate resume.
> 
> BugLink: http://bugs.launchpad.net/bugs/1333569
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Thanks for the resend. I was still planning to have a look at the patch
you send in September 2014. I believe that one replaces it.

I'll definitely have a look after 4.7-rc1.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com