linux-kernel - Re: [PATCH] Fix __wait_on_atomic_t() to call the action func if the counter != 0

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Message-ID: <20130723122629.6b5ae46e@tlielax.poochiereds.net>
Date:	Tue, 23 Jul 2013 12:26:29 -0400
From:	Jeff Layton <jlayton@...hat.com>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...ux-foundation.org, linux-nfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-cachefs@...hat.com,
	Milosz Tanski <milosz@...in.com>,
	Yacine Belkadi <yacine.belkadi.1@...il.com>
Subject: Re: [PATCH] Fix __wait_on_atomic_t() to call the action func if the
 counter != 0

On Tue, 23 Jul 2013 17:15:02 +0100
David Howells <dhowells@...hat.com> wrote:

> Jeff Layton <jlayton@...hat.com> wrote:
> 
> > > @@ -333,7 +333,8 @@ int __wait_on_atomic_t(wait_queue_head_t *wq, struct wait_bit_queue *q,
> > >  		prepare_to_wait(wq, &q->wait, mode);
> > >  		val = q->key.flags;
> > >  		if (atomic_read(val) == 0)
> > > -			ret = (*action)(val);
> > > +			break;
> > > +		ret = (*action)(val);
> > >  	} while (!ret && atomic_read(val) != 0);
> > 
> > nit: can you now eliminate the check for "val" in the while condition?
> > It doesn't look like it harms anything, but eliminating it would
> > probably simplify the code slightly...
> 
> Its presence means that we don't have to call prepare_to_wait() again if val
> became 0.
> 
> David

Ok, and prepare_to_wait involves taking spinlocks, etc...

Got it!

Reviewed-by: Jeff Layton <jlayton@...hat.com>
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