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: <BANLkTikpwk-hJs+TF7TJB38JsvOvHk2UMQ@mail.gmail.com>
Date:	Tue, 17 May 2011 08:15:38 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.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 8:11 AM, Tejun Heo <tj@...nel.org> wrote:
>
> Heh, okay.  It's not a lock tho.  It's multiple waiter waiting for a
> single event - so either explicit waitqueue or completion.  I was
> doing a waitqueue but bit waitqueue didn't seem to add too much
> complexity, so...

No.

Semantically what it is is a LOCK.

Turning it into something else just screws up everything.  It just
means you have to have ANOTHER lock to protect the things that the
completion/waitqueue would use.

Don't f*&^ around. Just make it a lock, and don't do a
"lock+completion " or something crazy.

If you can do it with a completion but with no locking, go ahead. I
doubt you can. You want the locking for the whole "do I need to wait
for the completion" thing anyway, so why mess things up?

                   Linus
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