linux-kernel - Re: hrtimer: one more expiry time overflow check in hrtimer

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Message-id: <51D6B300.20804@renesas.com>
Date:	Fri, 05 Jul 2013 20:50:24 +0900
From:	Shinya Kuribayashi <shinya.kuribayashi.px@...esas.com>
To:	tglx@...utronix.de
Cc:	prarit@...hat.com, john.stultz@...aro.org,
	hiroyuki.yokoyama.vx@...esas.com, takashi.yoshii.zj@...esas.com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: hrtimer: one more expiry time overflow check in hrtimer_interrupt

On 6/28/2013 9:22 PM, Thomas Gleixner wrote:
>> On the other hand, we have another call site of tick_program_event() at
>> the bottom of hrtimer_interrupt().  The warning this time is triggered
>> there, so we need to apply the same fix to it.
> 
> Well, the problem is that you are just papering over the underlying
> issue of 32bit systems not being prepared for the year 2038 issue.
> 
> Just blindly silencing the warning is not going to make the system
> survive 2038 in any sane way. All timespec/val related time functions
> dealing with the clock realtime domain are simply broken in 2038 on
> 32bit, so it does not matter whether a warning triggers or not.

You're right.  With this patch applied, the hrtimer_interrupt /looks/
back to normal, but /proc/timer_list still show that "expires at [in
negative range]":

    active timers:
     #0: tick_cpu_sched, tick_sched_timer, S:01
     # expires at 50812500000-50812500000 nsecs [in -165398341280 to -165398341280 nsecs]

This shouldn't happen and something weird is still going on.

> We really need to tackle the underlying problem and not bandaiding a
> known to be broken system.

Agreed, but a little bit hard task for me.  This is 100% reproducible,
so I can help debug / verification.  Please let me know, if necessary.

Thanks for your comments,
--
Shinya Kuribayashi
Renesas Electronics
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