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

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Date:	Tue, 24 Aug 2010 09:52:36 -0300
From:	Mauro Carvalho Chehab <mchehab@...radead.org>
To:	Richard Zidlicky <rz@...ux-m68k.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()

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).

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

---
 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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