linux-kernel - Re: [GIT PULL] sched: Cputime update for 3.10

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Message-ID: <CAFTL4hzTwiN8b8=SYVbt0NxMu1Y6ijO4-7aV1JVCBuvUbNmc5Q@mail.gmail.com>
Date:	Thu, 14 Mar 2013 13:39:35 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Stanislaw Gruszka <sgruszka@...hat.com>,
	Ingo Molnar <mingo@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] sched: Cputime update for 3.10

2013/3/14 Stanislaw Gruszka <sgruszka@...hat.com>:
> On Thu, Mar 14, 2013 at 08:14:27AM +0100, Ingo Molnar wrote:
>> Hm, is this a new bug? When was it introduced and is upstream affected as
>> well?
>
> Commit 0cf55e1ec08bb5a22e068309e2d8ba1180ab4239 start to use scalling
> for whole thread group, so increase chances of hitting multiplication
> overflow, depending on how many CPUs are on the system.

Yeah, it was introduced with that commit. Although problems was there
back when we started scaling cputime against precise sched runtime.
But certainly that commit 0cf55e1ec08bb5a22e068309e2d8ba1180ab4239
made the bug visible and happening in practice.

And indeed upstream is affected.
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