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fallbackswitch: Fix lock order problem between state and stream lock

Browse source 
The order is first stream lock, then state lock. Everything else can
lead to deadlocks.
This commit is contained in:
Sebastian Dröge 2022-09-27 12:22:36 +03:00
parent adb4cb8691
commit b6ebad2761
1 changed files with 37 additions and 18 deletions
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55
utils/fallbackswitch/src/fallbackswitch/imp.rs
View file

@ -759,12 +759,19 @@ impl FallbackSwitch {
return Ok(gst::FlowSuccess::Ok);
}
// Lock order: First stream lock then state lock!
let _stream_lock = MutexGuard::unlocked(&mut state, || self.src_pad.stream_lock());
is_active = self.active_sinkpad.lock().as_ref() == Some(pad);
if !is_active {
log!(CAT, obj: pad, "Dropping {:?} on inactive pad", buffer);
return Ok(gst::FlowSuccess::Ok);
}
let switched_pad = state.switched_pad;
let discont_pending = state.discont_pending;
state.switched_pad = false;
state.discont_pending = false;
let _stream_lock = self.src_pad.stream_lock();
drop(state);
if switched_pad {
@ -855,7 +862,6 @@ impl FallbackSwitch {
}
let mut state = self.state.lock();
let forward = self.active_sinkpad.lock().as_ref() == Some(pad);
let mut pad_state = pad.imp().state.lock();
@ -901,30 +907,43 @@ impl FallbackSwitch {
_ => {}
}
let fwd_sticky = if forward && state.switched_pad && event.is_serialized() {
drop(pad_state);
let mut is_active = self.active_sinkpad.lock().as_ref() == Some(pad);
if !is_active {
log!(CAT, obj: pad, "Dropping {:?} on inactive pad", event);
return true;
}
// Lock order: First stream lock then state lock!
let stream_lock_for_serialized = event
.is_serialized()
.then(|| MutexGuard::unlocked(&mut state, || self.src_pad.stream_lock()));
is_active = self.active_sinkpad.lock().as_ref() == Some(pad);
if !is_active {
log!(CAT, obj: pad, "Dropping {:?} on inactive pad", event);
return true;
}
let fwd_sticky = if state.switched_pad && stream_lock_for_serialized.is_some() {
state.switched_pad = false;
true
} else {
false
};
drop(pad_state);
let _stream_lock = forward.then(|| self.src_pad.stream_lock());
drop(state);
if forward {
if fwd_sticky {
let _ = pad.push_event(gst::event::Reconfigure::new());
pad.sticky_events_foreach(|event| {
self.src_pad.push_event(event.clone());
std::ops::ControlFlow::Continue(gst::EventForeachAction::Keep)
});
if fwd_sticky {
let _ = pad.push_event(gst::event::Reconfigure::new());
pad.sticky_events_foreach(|event| {
self.src_pad.push_event(event.clone());
std::ops::ControlFlow::Continue(gst::EventForeachAction::Keep)
});
element.notify(PROP_ACTIVE_PAD);
}
self.src_pad.push_event(event);
element.notify(PROP_ACTIVE_PAD);
}
true
self.src_pad.push_event(event)
}
fn sink_query(