aggregator: Take lock to ensure set_caps is not called concurently

Avoiding to be in an inconsistent state where we do not have
actual negotiate caps set as srccaps and leading to point where we
try to unref ->srccaps when they have already been set to NULL.

https://bugzilla.gnome.org/show_bug.cgi?id=735042

diff --git a/libs/gst/base/gstaggregator.c b/libs/gst/base/gstaggregator.c
index bc53044..8f53512 100644 (file)
--- a/libs/gst/base/gstaggregator.c
+++ b/libs/gst/base/gstaggregator.c
@@ -106,6 +106,22 @@ GST_DEBUG_CATEGORY_STATIC (aggregator_debug);
   g_cond_broadcast(&(((GstAggregatorPad* )pad)->priv->event_cond)); \
   }
 
+#define GST_AGGREGATOR_SETCAPS_LOCK(self)   G_STMT_START {        \
+  GST_LOG_OBJECT (self, "Taking SETCAPS lock from thread %p",   \
+        g_thread_self());                                         \
+  g_mutex_lock(&self->priv->setcaps_lock);                         \
+  GST_LOG_OBJECT (self, "Took SETCAPS lock from thread %p",     \
+        g_thread_self());                                         \
+  } G_STMT_END
+
+#define GST_AGGREGATOR_SETCAPS_UNLOCK(self)   G_STMT_START {        \
+  GST_LOG_OBJECT (self, "Releasing SETCAPS lock from thread %p",  \
+        g_thread_self());                                           \
+  g_mutex_unlock(&self->priv->setcaps_lock);                         \
+  GST_LOG_OBJECT (self, "Took SETCAPS lock from thread %p",       \
+        g_thread_self());                                           \
+  } G_STMT_END
+
 struct _GstAggregatorPadPrivate
 {
   gboolean pending_flush_start;
@@ -177,6 +193,9 @@ struct _GstAggregatorPrivate
 
   GstTagList *tags;
   gboolean tags_changed;
+
+  /* Lock to prevent two src setcaps from happening at the same time  */
+  GMutex setcaps_lock;
 };
 
 typedef struct
@@ -347,8 +366,10 @@ _push_mandatory_events (GstAggregator * self)
 void
 gst_aggregator_set_src_caps (GstAggregator * self, GstCaps * caps)
 {
+  GST_AGGREGATOR_SETCAPS_LOCK (self);
   gst_caps_replace (&self->priv->srccaps, caps);
   _push_mandatory_events (self);
+  GST_AGGREGATOR_SETCAPS_UNLOCK (self);
 }
 
 /**
@@ -1053,6 +1074,7 @@ gst_aggregator_finalize (GObject * object)
   GstAggregator *self = (GstAggregator *) object;
 
   g_mutex_clear (&self->priv->mcontext_lock);
+  g_mutex_clear (&self->priv->setcaps_lock);
 
   G_OBJECT_CLASS (aggregator_parent_class)->finalize (object);
 }
@@ -1134,6 +1156,7 @@ gst_aggregator_init (GstAggregator * self, GstAggregatorClass * klass)
   gst_element_add_pad (GST_ELEMENT (self), self->srcpad);
 
   g_mutex_init (&self->priv->mcontext_lock);
+  g_mutex_init (&self->priv->setcaps_lock);
 }
 
 /* we can't use G_DEFINE_ABSTRACT_TYPE because we need the klass in the _init