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

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Message-ID: <20130723120258.01024e81@tlielax.poochiereds.net>
Date:	Tue, 23 Jul 2013 12:02:58 -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 16:49:24 +0100
David Howells <dhowells@...hat.com> wrote:

> Fix __wait_on_atomic_t() so that it calls the action func if the counter != 0
> rather than if the counter is 0 so as to be analogous to __wait_on_bit().
> 
> Thanks to Yacine who found this by visual inspection.
> 
> This will affect FS-Cache in that it will could fail to sleep correctly when
> trying to clean up after a netfs cookie is withdrawn.
> 
> Reported-by: Yacine Belkadi <yacine.belkadi.1@...il.com>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Yacine Belkadi <yacine.belkadi.1@...il.com>
> cc: Milosz Tanski <milosz@...in.com>
> cc: Jeff Layton <jlayton@...hat.com>
> ---
> 
>  kernel/wait.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/wait.c b/kernel/wait.c
> index ce0daa3..dec68bd 100644
> --- a/kernel/wait.c
> +++ b/kernel/wait.c
> @@ -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...

>  	finish_wait(wq, &q->wait);
>  	return ret;
> 
> --
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-- 
Jeff Layton <jlayton@...hat.com>
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