linux-kernel - Re: [PATCH] clocksource, prevent overflow in clocksource

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Message-ID: <4F900DD6.50105@redhat.com>
Date:	Thu, 19 Apr 2012 09:06:30 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	John Stultz <john.stultz@...aro.org>, linux-kernel@...r.kernel.org,
	Salman Qazi <sqazi@...gle.com>, stable@...nel.org
Subject: Re: [PATCH] clocksource, prevent overflow in clocksource_cyc2ns



On 04/19/2012 08:52 AM, Thomas Gleixner wrote:
> On Thu, 19 Apr 2012, Thomas Gleixner wrote:
> 
>> On Wed, 18 Apr 2012, John Stultz wrote:
>>> On 04/18/2012 04:59 PM, Prarit Bhargava wrote:
>>>>

>> No. The show_state() part prints into the buffer. But it's not
>> guaranteed that the buffer is flushed right away. It could be flushed
>> later as well in a different context. And of course the flush code
>> runs with interrupts disabled and dumping out a gazillion of lines
>> over serial will cause the same hickup. Just planting random
>> touch_watchdog() calls into the code is not the right approach,
>> really.
>>
>> We should think about the reasons why we have interrupts disabled for
>> so much time. Is that really, really necessary ?

In the case of the sysrq-t, I would argue that it is.  The whole point behind
the sysrq-t is that we're capturing the *current* state of the system.  Having
that output effected by interrupts seems like a bad idea.

> 
> I'm not against making the clocksource code more robust, but I don't
> want to add crap there just to cope with complete madness elsewhere.

Maybe I came off the wrong way but I completely agree with that sentiment.  Like
yourself, I'm looking for a correct fix rather than a fast fix.

Sorry that I haven't provided any debug info but I'm still in the gathering data
stage atm.  It was just John's ping that made me "brain dump" the current info I
had.

P.
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