linux-kernel - Re: [PATCH RESEND 2/3 v2.6.39-rc7] block: make disk_block_events() properly wait for work cancellation

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Message-ID: <20110518050729.GA16870@mtj.dyndns.org>
Date:	Wed, 18 May 2011 07:07:29 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jens Axboe <axboe@...nel.dk>, Sitsofe Wheeler <sitsofe@...oo.com>,
	Borislav Petkov <bp@...en8.de>, Meelis Roos <mroos@...ux.ee>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kay Sievers <kay.sievers@...y.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 2/3 v2.6.39-rc7] block: make disk_block_events()
 properly wait for work cancellation

On Tue, May 17, 2011 at 03:40:11PM -0700, Linus Torvalds wrote:
> On Tue, May 17, 2011 at 8:27 AM, Tejun Heo <tj@...nel.org> wrote:
> >
> > Spinlock inside mutex seemed a bit strange but yeah that probably is
> > the simpliest way.
> 
> Do you really even need the spinlock at all?

There were sites which called disk_unblock/check_events() with
bdevlock held, which was why it was made spinlock in the first place.
Hmmm... they're not there anymore.

> Just make the semaphore protect the count - and you're done.

Yeah, with that gone, we don't even need the open-coding inside
disk_check_events().  It can simply call syncing block and unblock.
But, do you want that in -rc7?  Unnecessarily complicated as the
current code may be, converting the lock to mutex is a larger change
than adding an outer mutex and I think it would be better to do that
during the next cycle.

Thanks.

--
tejun
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