linux-kernel - Re: [PATCH v2 5/6] blk-mq: fix freeze queue race

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Message-ID: <20150709213405.GB18734@mtj.duckdns.org>
Date:	Thu, 9 Jul 2015 17:34:05 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Akinobu Mita <akinobu.mita@...il.com>
Cc:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
	Ming Lei <tom.leiming@...il.com>
Subject: Re: [PATCH v2 5/6] blk-mq: fix freeze queue race

On Thu, Jul 02, 2015 at 11:29:56PM +0900, Akinobu Mita wrote:
> There are several race conditions while freezing queue.
...
> Also, percpu_ref_reinit() and percpu_ref_kill() must not be executed
> at the same time.  Because both functions could call
> __percpu_ref_switch_to_percpu() which adds the bias value and
> initialize percpu counter.
> 
> Fix those races by serializing with per-queue mutex.
> 
> Signed-off-by: Akinobu Mita <akinobu.mita@...il.com>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Ming Lei <tom.leiming@...il.com>

Yeap, all of the kill/reinit/switch mode functions assume caller side
synchronization.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun
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