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queue2: fix event/preroll deadlock differently

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The qlock is released between popping a buffer from the queue
and pushing it. When this buffer causes the sink to wait in
preroll, this lets a query see that the queue is empty, and
push the query then wait for it to be serviced. However, this
will not be done till after peroll, and this will thus block.
If upstream was waiting on buffering to reach 100% before
switching to PLAYING, a deadlock would ensue.

This had been fixed recently by failing queries when the
queue2 was buffering, but this happens to break some other
case (playbin on a local http server and matroska), while
this patch works for both.

See https://bugzilla.gnome.org/show_bug.cgi?id=728345
This commit is contained in:
Vincent Penquerc'h 2014-04-16 15:17:04 +01:00
parent 145517aa64
commit f3dd7937a2
2 changed files with 24 additions and 7 deletions
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19
plugins/elements/gstqueue2.c
View file

@ -2339,14 +2339,21 @@ gst_queue2_handle_sink_query (GstPad * pad, GstObject * parent,
* completely, which can not happen if we block on the query..
* Therefore we only potentially block when we are not buffering. */
GST_QUEUE2_MUTEX_LOCK_CHECK (queue, queue->sinkresult, out_flushing);
if (QUEUE_IS_USING_QUEUE (queue) && !queue->is_buffering) {
gst_queue2_locked_enqueue (queue, query, GST_QUEUE2_ITEM_TYPE_QUERY);
if (QUEUE_IS_USING_QUEUE (queue) && (gst_queue2_is_empty (queue)
|| !queue->use_buffering)) {
if (!g_atomic_int_get (&queue->downstream_may_block)) {
gst_queue2_locked_enqueue (queue, query,
GST_QUEUE2_ITEM_TYPE_QUERY);
STATUS (queue, queue->sinkpad, "wait for QUERY");
g_cond_wait (&queue->query_handled, &queue->qlock);
if (queue->sinkresult != GST_FLOW_OK)
goto out_flushing;
res = queue->last_query;
} else {
GST_DEBUG_OBJECT (queue, "refusing query, downstream might block");
res = FALSE;
}
} else {
GST_DEBUG_OBJECT (queue,
"refusing query, we are not using the queue");
@ -2588,6 +2595,10 @@ gst_queue2_push_one (GstQueue2 * queue)
goto no_item;
next:
STATUS (queue, queue->srcpad, "We have something dequeud");
g_atomic_int_set (&queue->downstream_may_block,
item_type == GST_QUEUE2_ITEM_TYPE_BUFFER ||
item_type == GST_QUEUE2_ITEM_TYPE_BUFFER_LIST);
GST_QUEUE2_MUTEX_UNLOCK (queue);
if (item_type == GST_QUEUE2_ITEM_TYPE_BUFFER) {
@ -2596,6 +2607,7 @@ next:
buffer = GST_BUFFER_CAST (data);
result = gst_pad_push (queue->srcpad, buffer);
g_atomic_int_set (&queue->downstream_may_block, 0);
/* need to check for srcresult here as well */
GST_QUEUE2_MUTEX_LOCK_CHECK (queue, queue->srcresult, out_flushing);
@ -2627,6 +2639,7 @@ next:
buffer_list = GST_BUFFER_LIST_CAST (data);
result = gst_pad_push_list (queue->srcpad, buffer_list);
g_atomic_int_set (&queue->downstream_may_block, 0);
/* need to check for srcresult here as well */
GST_QUEUE2_MUTEX_LOCK_CHECK (queue, queue->srcresult, out_flushing);
@ -2641,7 +2654,9 @@ next:
} else if (item_type == GST_QUEUE2_ITEM_TYPE_QUERY) {
GstQuery *query = GST_QUERY_CAST (data);
GST_LOG_OBJECT (queue->srcpad, "Peering query %p", query);
queue->last_query = gst_pad_peer_query (queue->srcpad, query);
GST_LOG_OBJECT (queue->srcpad, "Peered query");
GST_CAT_LOG_OBJECT (queue_dataflow, queue,
"did query %p, return %d", query, queue->last_query);
g_cond_signal (&queue->query_handled);

2
plugins/elements/gstqueue2.h
View file

@ -151,6 +151,8 @@ struct _GstQueue2
guint64 ring_buffer_max_size;
guint8 * ring_buffer;
volatile gint downstream_may_block;
};
struct _GstQueue2Class