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From: Tejun Heo <tj@kernel.org>
To: Ming Lei <tom.leiming@gmail.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>,
	linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>
Subject: Re: [PATCH v2 5/6] blk-mq: fix freeze queue race
Date: Thu, 9 Jul 2015 17:37:47 -0400	[thread overview]
Message-ID: <20150709213747.GC18734@mtj.duckdns.org> (raw)
In-Reply-To: <20150709145510.6b8e21a2@tom-T450>

On Thu, Jul 09, 2015 at 02:55:10PM +0800, Ming Lei wrote:
> This patch looks fine since at least changing DEAD state of percpu ref
> state should have been synchronized by caller.
> 
> Also looks __percpu_ref_switch_to_percpu() need to check if the refcount
> becomes dead after current switching, and seems something like following
> is needed:

Hmmm... but the caller is responsible for synchronization for these
operations.  If the state changes while waiting, it indicates a
synchronization bug and testing it one more time is kinda weird.  What
if it changes right after that test?

Thanks.

-- 
tejun

  reply	other threads:[~2015-07-09 21:37 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 [this message]
2015-07-10  8:08       ` Ming Lei
2015-07-09 21:34   ` Tejun Heo
2015-07-02 14:29 ` [PATCH v2 6/6] blk-mq: fix deadlock when reading cpu_list Akinobu Mita

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