[rhythmbox] xfade: hold stream lock for more of link_and_unblock_stream()

[Jonathan Matthew <jmatthew src gnome org>]

commit 9c9d0b53afc65bd2ecb171dfdf92794bac50ffac
Author: Jonathan Matthew <jonathan d14n org>
Date:   Sat Dec 5 20:42:40 2020 +1000

    xfade: hold stream lock for more of link_and_unblock_stream()
    
    In some situations this can be called concurrently on two threads,
    so it needs more protection.

 backends/gstreamer/rb-player-gst-xfade.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/backends/gstreamer/rb-player-gst-xfade.c b/backends/gstreamer/rb-player-gst-xfade.c
index 420cf7f65..98b4b1781 100644
--- a/backends/gstreamer/rb-player-gst-xfade.c
+++ b/backends/gstreamer/rb-player-gst-xfade.c
@@ -1087,8 +1087,10 @@ link_and_unblock_stream (RBXFadeStream *stream, GError **error)
                return FALSE;
        }
 
+       g_mutex_lock (&stream->lock);
        if (stream->adder_pad != NULL) {
                rb_debug ("stream %s is already linked", stream->uri);
+               g_mutex_unlock (&stream->lock);
                return TRUE;
        }
        stream->needs_unlink = FALSE;
@@ -1105,6 +1107,7 @@ link_and_unblock_stream (RBXFadeStream *stream, GError **error)
                             RB_PLAYER_ERROR,
                             RB_PLAYER_ERROR_GENERAL,
                             _("Failed to link new stream into GStreamer pipeline"));
+               g_mutex_unlock (&stream->lock);
                return FALSE;
        }
 
@@ -1120,14 +1123,13 @@ link_and_unblock_stream (RBXFadeStream *stream, GError **error)
                             RB_PLAYER_ERROR_GENERAL,
                             _("Failed to link new stream into GStreamer pipeline"));
                return FALSE;
+               g_mutex_unlock (&stream->lock);
        }
 
-
        g_atomic_int_inc (&player->priv->linked_streams);
        rb_debug ("now have %d linked streams", player->priv->linked_streams);
 
        result = TRUE;
-       g_mutex_lock (&stream->lock);
        if (stream->src_blocked) {
                GstStateChangeReturn state_ret;