linux-kernel - Re: [PATCH] blk-exec-assign-endio-before-queue-dead-check

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Message-ID: <CAOS58YPAOYcHYkXu7hW-DeGRXkFqoF1cLarJFfh0eNfFaVHyBg@mail.gmail.com>
Date:	Thu, 7 Jun 2012 14:53:24 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Muthu Kumar <muthu.lkml@...il.com>
Cc:	Jens Axboe <axboe@...nel.dk>,
	James.Bottomley@...senpartnership.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blk-exec-assign-endio-before-queue-dead-check

Hello,

On Thu, Jun 7, 2012 at 2:42 PM, Muthu Kumar <muthu.lkml@...il.com> wrote:
>>> One more thing to consider is, the completion function is called from
>>> the same calling context here. As far as my check, it looks ok. Let me
>>> know if you think otherwise.
>>
>> Not sure what you mean.
>
> If there is no error, then the completion routine is called in a
> different context - rq completion context. But here, we call the
> completion routine in the same context of the caller.

Ah, okay. I think the only problem there would be that the end_io
callback is being called outside queue lock. Can you please take care
of that too?

> blk-exec.c: In blk_execute_rq_nowait(), if the queue is dead, call to
> done() routine is not made. That will result in blk_execute_rq() stuck
> in wait_for_completion(). Avoid this by initializing rq->end_io to
> done() routine before we check for dead queue.

Yeah, sounds about right.

Thanks.

-- 
tejun
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