linux-kernel - Re: [patch]block: fix ioc locking warning

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Message-ID: <20120206172706.GB21292@google.com>
Date:	Mon, 6 Feb 2012 09:27:06 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Jens Axboe <axboe@...nel.dk>,
	Shaohua Li <vivek.goyal2008@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Knut Petersen <Knut_Petersen@...nline.de>, mroos@...ux.ee
Subject: Re: [patch]block: fix ioc locking warning

Hello,

On Mon, Feb 06, 2012 at 08:58:49AM -0800, Linus Torvalds wrote:
> On Mon, Feb 6, 2012 at 8:44 AM, Tejun Heo <tj@...nel.org> wrote:
> >
> > Yeah, this seems better to me.  Jens, if you're gonna amend the
> > commit, please consider collapsing the following patch into the
> > original patch too.  Thanks.
> 
> Guys, is it *really* worth it to do all these crazy games?
>
> How bad is it to just always use the async freeing, instead of this
> clearly very fragile crazy direct-freeing-with-serious-locking-issues
> thing?

It's one wq scheduling on exit for any task which has issued an IO.  I
don't think it would matter except for task fork/exit microbenchs (or
workloads which approximate to that).  I'll get some measurements and
strip the optimization if it doesn't really show up.

Thanks.

--
tejun
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