linux-kernel - Re: serial percpu_ref draining in exit

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Message-ID: <550B42EE.8030405@kernel.dk>
Date:	Thu, 19 Mar 2015 15:43:10 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Tejun Heo <tj@...nel.org>, Jeff Moyer <jmoyer@...hat.com>
CC:	kent.overstreet@...il.com, Benjamin LaHaise <bcrl@...ck.org>,
	linux-kernel@...r.kernel.org
Subject: Re: serial percpu_ref draining in exit_aio()

On 03/19/2015 03:27 PM, Jens Axboe wrote:
> On 03/19/2015 03:00 PM, Tejun Heo wrote:
>> On Thu, Mar 19, 2015 at 04:58:33PM -0400, Jeff Moyer wrote:
>>> Do you really want to do memory allocation in the exit path?  That
>>> sounds like a bad idea to me.  (Of course, now you're going to point out
>>> all the places that currently happens, right?  ;-)
>>
>> I think we just need a counter there - let everyone count down as they
>> exit and the last one trigger the completion, no?
>
> Yeah that's a good point, that'd be cleaner too. I'll change it and test
> that.

Here's a cleaner variant that pairs the completion even with an atomic 
count. Works for me as well.

-- 
Jens Axboe


View attachment "aio-exit-parallel-v2.patch" of type "text/x-patch" (3559 bytes)