linux-kernel - Re: [PATCH] sched: Fix the irqtime code to deal with u64 wraps

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Date:	Fri, 10 Dec 2010 21:23:01 -0500 (EST)
From:	Nicolas Pitre <nico@...xnic.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Venkatesh Pallipadi <venki@...gle.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Mikael Pettersson <mikpe@...uu.se>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	John Stultz <johnstul@...ibm.com>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH] sched: Fix the irqtime code to deal with u64 wraps

On Fri, 10 Dec 2010, Peter Zijlstra wrote:

> OK, so here's the latest version, using fancy __this_cpu thingies.
> 
> I started a new thread since the old one was quite unwieldy.
> 
> Now, admittedly this patch is a tad large, esp for -rc5. So either we
> need lots of Reviewed-by and such or I need to shrink this patch
> somehow.
> 
> 
> ---
> Subject: sched: Fix the irqtime code to deal with u64 wraps
> From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Date: Thu Dec 09 14:15:34 CET 2010
> 
> ARM systems have a 32bit sched_clock() [ which needs to be fixed ],
> but this exposed a bug in the irq_time code as well, it doesn't deal
> with wraps at all.
[...]

That would be more close to reality if you stated "Some ARM systems have 
a 32bit sched_clock() [" above.  Most ARM systems in use today have a 
sched_clock() with more than 32 bits, like 55 bits or so.


Nicolas
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