netdev - Re: [PATCH percpu/for-4.7-fixes 2/2] percpu: fix synchronization between synchronous map extension and chunk destruction

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Message-ID: <0613d173-2ff1-a904-9611-0c6fc254f45e@suse.cz>
Date:	Thu, 26 May 2016 11:48:41 +0200
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Tejun Heo <tj@...nel.org>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Alexei Starovoitov <ast@...nel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Linux-MM layout <linux-mm@...ck.org>,
	Marco Grassi <marco.gra@...il.com>, kernel-team@...com
Subject: Re: [PATCH percpu/for-4.7-fixes 2/2] percpu: fix synchronization
 between synchronous map extension and chunk destruction

On 05/25/2016 05:45 PM, Tejun Heo wrote:
> For non-atomic allocations, pcpu_alloc() can try to extend the area
> map synchronously after dropping pcpu_lock; however, the extension
> wasn't synchronized against chunk destruction and the chunk might get
> freed while extension is in progress.
>
> This patch fixes the bug by putting most of non-atomic allocations
> under pcpu_alloc_mutex to synchronize against pcpu_balance_work which
> is responsible for async chunk management including destruction.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-and-tested-by: Alexei Starovoitov <alexei.starovoitov@...il.com>
> Reported-by: Vlastimil Babka <vbabka@...e.cz>
> Reported-by: Sasha Levin <sasha.levin@...cle.com>
> Cc: stable@...r.kernel.org # v3.18+
> Fixes: 1a4d76076cda ("percpu: implement asynchronous chunk population")

Didn't spot any problems this time.

Thanks