fallbackswitch: prevent deadlocks in chain function

Calling schedule_timeout() may result in handle_timeout() being called right away,
which will need pad state locks which was still hold in chain().

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/1330>

1 files changed, 6 insertions, 1 deletions

diff --git a/utils/fallbackswitch/src/fallbackswitch/imp.rs b/utils/fallbackswitch/src/fallbackswitch/imp.rs
index 6be708ea3..3e76be4b4 100644
--- a/utils/fallbackswitch/src/fallbackswitch/imp.rs
+++ b/utils/fallbackswitch/src/fallbackswitch/imp.rs
@@ -829,11 +829,14 @@ impl FallbackSwitch {
             is_active = self.active_sinkpad.lock().as_ref() == Some(pad);
         }
 
-        let mut pad_state = pad_imp.state.lock();
+        let pad_state = pad_imp.state.lock();
         if pad_state.flushing {
             debug!(CAT, imp: self, "Flushing");
             return Err(gst::FlowError::Flushing);
         }
+        // calling schedule_timeout() may result in handle_timeout() being called right away,
+        // which will need pad state locks, so drop it now to prevent deadlocks.
+        drop(pad_state);
 
         if is_active {
             if start_running_time
@@ -879,6 +882,8 @@ impl FallbackSwitch {
             }
         }
 
+        let mut pad_state = pad_imp.state.lock();
+
         if let Some(running_time) = end_running_time {
             pad_state.current_running_time = Some(running_time);
         }