linux-kernel - [PATCH 2.6.34] schedule inside spin_lock

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Date:	Sun, 6 Jun 2010 14:43:02 +0200
From:	Richard Zidlicky <rz@...ux-m68k.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: [PATCH 2.6.34] schedule inside spin_lock_irqsave

Hi,

I have done a minimaly invasive patch for the stable 2.6.34 kernel and stress-tested 
it for many hours, definitely seems to improve the behaviour.

I have left out your beautification suggestion for now, want to do more playing with
other aspects of the driver. There still seem to be issues when the device is unplugged 
while in use and such.

--- 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	2010-06-04 23:00:35.000000000 +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(void)
 {
 	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()));
 
 	return cb;
 }


Richard
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