pad: block data flow when idle probe is running

When idle probe runs directly from the gst_pad_add_probe() function
we need to make sure that no data flow happens as idle probe
is a blocking probe. The idle probe will prevent that any
buffer, bufferlist or serialized events and queries are not
flowing while it is running.

https://bugzilla.gnome.org/show_bug.cgi?id=747852

diff --git a/gst/gstpad.c b/gst/gstpad.c
index b762465..a7e1c37 100644 (file)
--- a/gst/gstpad.c
+++ b/gst/gstpad.c
@@ -140,6 +140,11 @@ struct _GstPadPrivate
   gint using;
   guint probe_list_cookie;
   guint probe_cookie;
+
+  /* counter of how many idle probes are running directly from the add_probe
+   * call. Used to block any data flowing in the pad while the idle callback
+   * Doesn't finish its work */
+  gint idle_running;
 };
 
 typedef struct
@@ -149,6 +154,8 @@ typedef struct
 } GstProbe;
 
 #define PROBE_COOKIE(h) (((GstProbe *)(h))->cookie)
+#define GST_PAD_IS_RUNNING_IDLE_PROBE(p) \
+    (((GstPad *)(p))->priv->idle_running > 0)
 
 typedef struct
 {
@@ -1387,6 +1394,7 @@ gst_pad_add_probe (GstPad * pad, GstPadProbeType mask,
 
       /* Keep another ref, the callback could destroy the pad */
       gst_object_ref (pad);
+      pad->priv->idle_running++;
 
       /* the pad is idle now, we can signal the idle callback now */
       GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
@@ -1416,6 +1424,10 @@ gst_pad_add_probe (GstPad * pad, GstPadProbeType mask,
           GST_DEBUG_OBJECT (pad, "probe returned %d", ret);
           break;
       }
+      pad->priv->idle_running--;
+      if (pad->priv->idle_running == 0) {
+        GST_PAD_BLOCK_BROADCAST (pad);
+      }
       GST_OBJECT_UNLOCK (pad);
 
       gst_object_unref (pad);
@@ -3402,6 +3414,38 @@ no_match:
   PROBE_FULL(pad, mask, data, offs, size, label);
 
 static GstFlowReturn
+do_pad_idle_probe_wait (GstPad * pad)
+{
+  while (GST_PAD_IS_RUNNING_IDLE_PROBE (pad)) {
+    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
+        "waiting idle probe to be removed");
+    GST_OBJECT_FLAG_SET (pad, GST_PAD_FLAG_BLOCKING);
+    GST_PAD_BLOCK_WAIT (pad);
+    GST_OBJECT_FLAG_UNSET (pad, GST_PAD_FLAG_BLOCKING);
+    GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad, "We got unblocked");
+
+    if (G_UNLIKELY (GST_PAD_IS_FLUSHING (pad)))
+      return GST_FLOW_FLUSHING;
+  }
+  return GST_FLOW_OK;
+}
+
+#define PROBE_TYPE_IS_SERIALIZED(i) \
+    ( \
+      ( \
+        (((i)->type & (GST_PAD_PROBE_TYPE_EVENT_DOWNSTREAM | \
+        GST_PAD_PROBE_TYPE_EVENT_FLUSH)) && \
+        GST_EVENT_IS_SERIALIZED ((i)->data)) \
+      ) || ( \
+        (((i)->type & GST_PAD_PROBE_TYPE_QUERY_DOWNSTREAM) && \
+        GST_QUERY_IS_SERIALIZED ((i)->data)) \
+      ) || ( \
+        ((i)->type & (GST_PAD_PROBE_TYPE_BUFFER | \
+        GST_PAD_PROBE_TYPE_BUFFER_LIST))  \
+      ) \
+    )
+
+static GstFlowReturn
 do_probe_callbacks (GstPad * pad, GstPadProbeInfo * info,
     GstFlowReturn defaultval)
 {
@@ -3419,6 +3463,11 @@ do_probe_callbacks (GstPad * pad, GstPadProbeInfo * info,
   is_block =
       (info->type & GST_PAD_PROBE_TYPE_BLOCK) == GST_PAD_PROBE_TYPE_BLOCK;
 
+  if (is_block && PROBE_TYPE_IS_SERIALIZED (info)) {
+    if (do_pad_idle_probe_wait (pad) == GST_FLOW_FLUSHING)
+      goto flushing;
+  }
+
 again:
   GST_CAT_LOG_OBJECT (GST_CAT_SCHEDULING, pad,
       "do probes cookie %u", data.cookie);