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

[Richard Zidlicky <rz@linux-m68k.org>]

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.

Richard


--- linux-2.6.34/drivers/media/dvb/siano/smscoreapi.c.rz	2010-06-03 21:58:11.000000000 +0200
+++ linux-2.6.34/drivers/media/dvb/siano/smscoreapi.c	2010-06-07 14:32:06.000000000 +0200
@@ -1100,31 +1100,26 @@
  *
  * @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);
-
-	/* 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);
-
+	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;
+}
+
+struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t *coredev)
+{
+	struct smscore_buffer_t *cb = NULL;
+
+	wait_event(coredev->buffer_mng_waitq, (cb = get_entry(coredev)));
 
 	return cb;
 }