Hi,
This patch step is a Bug fix - avoid (rare) dead locks causing the
driver to hang when module removed.
Thanks,
Doron Cohen
-----------------------
>From ad75d9ce48d440c6db6c5147530f1e23de2fcb28 Mon Sep 17 00:00:00 2001
From: Doron Cohen <dor...@siano-ms.com>
Date: Tue, 20 Sep 2011 08:46:52 +0300
Subject: [PATCH 19/21] Bug fix - waiting for free buffers might have
caused dead locks. Mechanism changed so locks are released around each
wait.
---
drivers/media/dvb/siano/smscoreapi.c | 53
+++++++++++++++++++++++++++------
1 files changed, 43 insertions(+), 10 deletions(-)
diff --git a/drivers/media/dvb/siano/smscoreapi.c
b/drivers/media/dvb/siano/smscoreapi.c
index bb92351..0555a38 100644
--- a/drivers/media/dvb/siano/smscoreapi.c
+++ b/drivers/media/dvb/siano/smscoreapi.c
@@ -1543,26 +1543,59 @@ EXPORT_SYMBOL_GPL(smscore_onresponse);
*
* @return pointer to descriptor on success, NULL on error.
*/
-
-struct smscore_buffer_t *get_entry(struct smscore_device_t *coredev)
+struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t
*coredev)
{
struct smscore_buffer_t *cb = NULL;
unsigned long flags;
+ DEFINE_WAIT(wait);
+
+ spin_lock_irqsave(&coredev->bufferslock, flags);
+
+ /* set the current process state to interruptible sleep
+ * in case schedule() will be called, this process will go to sleep
+ * and woken up only when a new buffer is available (see
smscore_putbuffer)
+ */
+ prepare_to_wait(&coredev->buffer_mng_waitq, &wait,
TASK_INTERRUPTIBLE);
+
+ if (list_empty(&coredev->buffers)) {
+ sms_debug("no avaliable common buffer, need to schedule");
+
+ /*
+ * before going to sleep, release the lock
+ */
+ spin_unlock_irqrestore(&coredev->bufferslock, flags);
+
+ schedule();
+
+ sms_debug("wake up after schedule()");
+
+ /*
+ * acquire the lock again
+ */
spin_lock_irqsave(&coredev->bufferslock, flags);
- if (!list_empty(&coredev->buffers)) {
- cb = (struct smscore_buffer_t *) coredev->buffers.next;
- list_del(&cb->entry);
}
+
+ /*
+ * in case that schedule() was skipped, set the process state
to running
+ */
+ finish_wait(&coredev->buffer_mng_waitq, &wait);
+
+ /*
+ * verify that the list is not empty, since it might have been
+ * emptied during the sleep
+ * comment : this sitation can be avoided using
spin_unlock_irqrestore_exclusive
+ */
+ if (list_empty(&coredev->buffers)) {
+ sms_err("failed to allocate buffer, returning NULL");
spin_unlock_irqrestore(&coredev->bufferslock, flags);
- return cb;
+ return NULL;
}
-struct smscore_buffer_t *smscore_getbuffer(struct smscore_device_t
*coredev)
-{
- struct smscore_buffer_t *cb = NULL;
+ cb = (struct smscore_buffer_t *) coredev->buffers.next;
+ list_del(&cb->entry);
- wait_event(coredev->buffer_mng_waitq, (cb = get_entry(coredev)));
+ spin_unlock_irqrestore(&coredev->bufferslock, flags);
return cb;
}
--
1.7.4.1
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