linux-kernel - Re: [PATCH] dvb: siano: free spinlock before schedule()

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Date:	Tue, 24 Aug 2010 17:43:18 +0200
From:	Richard Zidlicky <rz@...ux-m68k.org>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
Cc:	Jiri Slaby <jirislaby@...il.com>,
	Kulikov Vasiliy <segooon@...il.com>,
	kernel-janitors@...r.kernel.org,
	Douglas Schilling Landgraf <dougsland@...hat.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Roel Kluin <roel.kluin@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dvb: siano: free spinlock before schedule()

On Tue, Aug 24, 2010 at 09:52:36AM -0300, Mauro Carvalho Chehab wrote:
> Em 08-08-2010 13:10, Richard Zidlicky escreveu:
> > On Wed, Jul 28, 2010 at 12:24:39AM +0200, Jiri Slaby wrote:
> > 
> > sorry for seeing this so late, was flooded with email lately.
> > 
> >> There is a better fix (which fixes the potential NULL dereference):
> >> http://lkml.org/lkml/2010/6/7/175
> > 
> >> Richard, could you address the comments there and resend?
> > 
> > I am running this patch since many weeks (after fixing the compile error obviously). 
> > Did not implement your beautification suggestion yet, was doing all kinds of experiments
> > with IR and had plenty of unrelated issues.
> 
> This patch seems a way better than the previous patch. I've rebased it against
> the current tree (and fixed the identation).

thanks for looking at it.

> The only missing issue on it is the lack of your Signed-off-by. Richard, could you
> please send it to us?


Signed-off-by: Richard Zidlicky <rz@...ux-m68k.org>

PS: I will be away for a while.

> 
> ---
>  drivers/media/dvb/siano/smscoreapi.c |   31 +++++++++++++------------------
>  1 file changed, 13 insertions(+), 18 deletions(-)
> 
> --- patchwork.orig/drivers/media/dvb/siano/smscoreapi.c
> +++ patchwork/drivers/media/dvb/siano/smscoreapi.c
> @@ -1098,31 +1098,26 @@ EXPORT_SYMBOL_GPL(smscore_onresponse);
>   *
>   * @return pointer to descriptor on success, NULL on error.
>   */
> -struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t *coredev)
> +
> +struct smscore_buffer_t *get_entry(struct smscore_device_t *coredev)
>  {
>  	struct smscore_buffer_t *cb = NULL;
>  	unsigned long flags;
>  
> -	DEFINE_WAIT(wait);
> -
>  	spin_lock_irqsave(&coredev->bufferslock, flags);
> +	if (!list_empty(&coredev->buffers)) {
> +		cb = (struct smscore_buffer_t *) coredev->buffers.next;
> +		list_del(&cb->entry);
> +	}
> +	spin_unlock_irqrestore(&coredev->bufferslock, flags);
> +	return cb;
> +}
>  
> -	/* This function must return a valid buffer, since the buffer list is
> -	 * finite, we check that there is an available buffer, if not, we wait
> -	 * until such buffer become available.
> -	 */
> -
> -	prepare_to_wait(&coredev->buffer_mng_waitq, &wait, TASK_INTERRUPTIBLE);
> -
> -	if (list_empty(&coredev->buffers))
> -		schedule();
> -
> -	finish_wait(&coredev->buffer_mng_waitq, &wait);
> -
> -	cb = (struct smscore_buffer_t *) coredev->buffers.next;
> -	list_del(&cb->entry);
> +struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t *coredev)
> +{
> +	struct smscore_buffer_t *cb = NULL;
>  
> -	spin_unlock_irqrestore(&coredev->bufferslock, flags);
> +	wait_event(coredev->buffer_mng_waitq, (cb = get_entry(coredev)));
>  
>  	return cb;
>  }
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