linux-kernel - Re: [PATCH] aio: Wake all waiters when destroying ctx

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Date:	Fri, 11 Mar 2011 09:21:46 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Roland Dreier <roland@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-aio@...ck.org,
	linux-kernel@...r.kernel.org, Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [PATCH] aio: Wake all waiters when destroying ctx

Roland Dreier <roland@...nel.org> writes:

> From: Roland Dreier <roland@...estorage.com>
>
> The test program below will hang because io_getevents() uses
> add_wait_queue_exclusive(), which means the wake_up() in io_destroy()
> only wakes up one of the threads.  Fix this by using wake_up_all() in
> the aio code paths where we want to make sure no one gets stuck.

[snip]

> Cc: <stable@...nel.org>
> Signed-off-by: Roland Dreier <roland@...estorage.com>
> ---
>  fs/aio.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 26869cd..88f0ed5 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -520,7 +520,7 @@ static inline void really_put_req(struct kioctx *ctx, struct kiocb *req)
>  	ctx->reqs_active--;
>  
>  	if (unlikely(!ctx->reqs_active && ctx->dead))
> -		wake_up(&ctx->wait);
> +		wake_up_all(&ctx->wait);
>  }
>  
>  static void aio_fput_routine(struct work_struct *data)
> @@ -1229,7 +1229,7 @@ static void io_destroy(struct kioctx *ioctx)
>  	 * by other CPUs at this point.  Right now, we rely on the
>  	 * locking done by the above calls to ensure this consistency.
>  	 */
> -	wake_up(&ioctx->wait);
> +	wake_up_all(&ioctx->wait);
>  	put_ioctx(ioctx);	/* once for the lookup */
>  }
>  

Thanks, Roland, this looks good.

Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
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