linux-kernel - Re: [PATCH v5 8/8] sched/numa: drop unnecessary variable in task

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Message-ID: <1386773428-bwklwan0-mutt-n-horiguchi@ah.jp.nec.com>
Date:	Wed, 11 Dec 2013 09:50:28 -0500
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v5 8/8] sched/numa: drop unnecessary variable in
 task_weight

On Wed, Dec 11, 2013 at 09:21:23AM +0000, Mel Gorman wrote:
> On Wed, Dec 11, 2013 at 08:50:01AM +0800, Wanpeng Li wrote:
> > Drop unnecessary total_faults variable in function task_weight to unify
> > task_weight and group_weight.
> > 
> > Reviewed-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> > Signed-off-by: Wanpeng Li <liwanp@...ux.vnet.ibm.com>
> 
> Nak.
> 
> task_weight is called for tasks other than current. If p handles a fault
> in parallel then it can drop to 0 between when it's checked and used to
> divide resulting in an oops.

So we have the same race on group_weight(), and we have to add a local
variable to store p->numa_group->total_faults?

Thanks,
Naoya Horiguchi
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