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From: Tejun Heo <tj@kernel.org>
To: Akinobu Mita <akinobu.mita@gmail.com>
Cc: linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	Ming Lei <tom.leiming@gmail.com>
Subject: Re: [PATCH v2 5/6] blk-mq: fix freeze queue race
Date: Thu, 9 Jul 2015 17:34:05 -0400	[thread overview]
Message-ID: <20150709213405.GB18734@mtj.duckdns.org> (raw)
In-Reply-To: <1435847397-724-6-git-send-email-akinobu.mita@gmail.com>

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@gmail.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: Ming Lei <tom.leiming@gmail.com>

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

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

Thanks.

-- 
tejun

  parent reply	other threads:[~2015-07-09 21:34 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-07-02 14:29 [PATCH v2 0/6] blk-mq: fix race conditions on cpu hotplug handling Akinobu Mita
2015-07-02 14:29 ` [PATCH v2 1/6] blk-mq: fix sysfs registration/unregistration race Akinobu Mita
2015-07-08 11:48   ` Ming Lei
2015-07-09 14:25     ` Akinobu Mita
2015-07-09 14:43       ` Ming Lei
2015-07-02 14:29 ` [PATCH v2 2/6] blk-mq: Fix use after of free q->mq_map Akinobu Mita
2015-07-08 11:53   ` Ming Lei
2015-07-02 14:29 ` [PATCH v2 3/6] blk-mq: fix q->mq_usage_counter access race Akinobu Mita
2015-07-08 11:53   ` Ming Lei
2015-07-02 14:29 ` [PATCH v2 4/6] blk-mq: avoid inserting requests before establishing new mapping Akinobu Mita
2015-07-09  7:04   ` Ming Lei
2015-07-02 14:29 ` [PATCH v2 5/6] blk-mq: fix freeze queue race Akinobu Mita
2015-07-09  6:55   ` Ming Lei
2015-07-09 21:37     ` Tejun Heo
2015-07-10  8:08       ` Ming Lei
2015-07-09 21:34   ` Tejun Heo [this message]
2015-07-02 14:29 ` [PATCH v2 6/6] blk-mq: fix deadlock when reading cpu_list Akinobu Mita

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