linux-kernel - Re: [PATCH 3/3] blk-mq: Fix the queue freezing mechanism

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Message-ID: <20150924181430.GD25415@mtj.duckdns.org>
Date:	Thu, 24 Sep 2015 14:14:30 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Bart Van Assche <bart.vanassche@...disk.com>
Cc:	Ming Lei <tom.leiming@...il.com>, Jens Axboe <axboe@...com>,
	Christoph Hellwig <hch@....de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Akinobu Mita <akinobu.mita@...il.com>
Subject: Re: [PATCH 3/3] blk-mq: Fix the queue freezing mechanism

Hello,

On Thu, Sep 24, 2015 at 11:09:33AM -0700, Bart Van Assche wrote:
> On 09/24/2015 10:49 AM, Tejun Heo wrote:
> > Again, that doesn't happen.
> 
> Hello Tejun,
> 
> In case anyone would be interested, the backtraces for the lockup I had
> observed are as follows:

If this is happening and it's not caused by a hung in-flight request,
it's either percpu_ref being buggy or the forementioned kill/reinit
race screwing it up.  percpu_ref_kill() is expected to disable
tryget_live() in a finite amount of time regardless of concurrent
tryget tries.

Thanks.

-- 
tejun
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