linux-kernel - Re: [PATCH v3 1/3] sched/cpuacct: fix charge percpu cpuusage

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Message-ID: <YhX6Pg67eYf1jrOG@hirez.programming.kicks-ass.net>
Date:   Wed, 23 Feb 2022 10:11:26 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     Chengming Zhou <zhouchengming@...edance.com>, mingo@...hat.com,
        vincent.guittot@...aro.org, bristot@...hat.com,
        zhaolei@...fujitsu.com, lizefan.x@...edance.com,
        hannes@...xchg.org, linux-kernel@...r.kernel.org,
        Minye Zhu <zhuminye@...edance.com>
Subject: Re: [PATCH v3 1/3] sched/cpuacct: fix charge percpu cpuusage

On Tue, Feb 22, 2022 at 08:01:51AM -1000, Tejun Heo wrote:
> On Sun, Feb 20, 2022 at 01:14:24PM +0800, Chengming Zhou wrote:
> > The cpuacct_account_field() is always called by the current task
> > itself, so it's ok to use __this_cpu_add() to charge the tick time.
> > 
> > But cpuacct_charge() maybe called by update_curr() in load_balance()
> > on a random CPU, different from the CPU on which the task is running.
> > So __this_cpu_add() will charge that cputime to a random incorrect CPU.
> > 
> > Fixes: 73e6aafd9ea8 ("sched/cpuacct: Simplify the cpuacct code")
> > Reported-by: Minye Zhu <zhuminye@...edance.com>
> > Signed-off-by: Chengming Zhou <zhouchengming@...edance.com>
> 
> For all three patches,
> 
> Acked-by: Tejun Heo <tj@...nel.org>

Thanks!