[0.11] gstreamer: multiqueue: Increment unique item counter with atomic operations

[Edward Hervey]

Module: gstreamer
Branch: 0.11
Commit: 383cac91b103fa4b133428cc6196f35a1cd7904d
URL:    http://cgit.freedesktop.org/gstreamer/gstreamer/commit/?id=383cac91b103fa4b133428cc6196f35a1cd7904d

Author: Sebastian Dröge <sebastian.droege at collabora.co.uk>
Date:   Mon Mar 21 17:52:13 2011 +0100

multiqueue: Increment unique item counter with atomic operations

Before it was only protected by the stream lock but every pad
has its own stream lock, making the protection rather useless.

---

 plugins/elements/gstmultiqueue.c |    7 +++----
 plugins/elements/gstmultiqueue.h |    2 +-
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/plugins/elements/gstmultiqueue.c b/plugins/elements/gstmultiqueue.c
index f1956da..3f1eef5 100644
--- a/plugins/elements/gstmultiqueue.c
+++ b/plugins/elements/gstmultiqueue.c
@@ -1229,7 +1229,7 @@ gst_multi_queue_chain (GstPad * pad, GstBuffer * buffer)
     goto was_eos;
 
   /* Get a unique incrementing id */
-  curid = mq->counter++;
+  curid = g_atomic_int_exchange_and_add ((gint *) & mq->counter, 1);
 
   GST_LOG_OBJECT (mq, "SingleQueue %d : about to enqueue buffer %p with id %d",
       sq->id, buffer, curid);
@@ -1334,9 +1334,8 @@ gst_multi_queue_sink_event (GstPad * pad, GstEvent * event)
   if (sq->is_eos)
     goto was_eos;
 
-  /* Get an unique incrementing id. protected with the STREAM_LOCK, unserialized
-   * events already got pushed and don't end up in the queue. */
-  curid = mq->counter++;
+  /* Get an unique incrementing id. */
+  curid = g_atomic_int_exchange_and_add ((gint *) & mq->counter, 1);
 
   item = gst_multi_queue_event_item_new ((GstMiniObject *) event, curid);
 
diff --git a/plugins/elements/gstmultiqueue.h b/plugins/elements/gstmultiqueue.h
index ec47601..60262b7 100644
--- a/plugins/elements/gstmultiqueue.h
+++ b/plugins/elements/gstmultiqueue.h
@@ -63,7 +63,7 @@ struct _GstMultiQueue {
   gboolean buffering;
   gint percent;
 
-  guint32  counter;	/* incoming object counter, protected with STREAM_LOCK */
+  guint32  counter;	/* incoming object counter, use atomic accesses */
   guint32  highid;	/* contains highest id of last outputted object */
 
   GMutex * qlock;	/* Global queue lock (vs object lock or individual */