tor-browser

commit 0bf980d7abf0f0fa3cb9c8904556fe7de61ffb10
parent d0a896ca628bff9eb5710a19bf34849e4ddc0fcf
Author: alwu <alwu@mozilla.com>
Date:   Wed, 22 Oct 2025 18:53:29 +0000

Bug 1990812 - handle the case where switching the decoder state machine fails due to shutdown. r=media-playback-reviewers,chunmin

We will not create a new state machine if the decoder has already been shut
down. In this case, the old state machine will still report as unsupported,
which currently triggers a MOZ_DIAGNOSTIC_CRASH.

Instead of crashing, we should simply reject the promise.

Differential Revision: https://phabricator.services.mozilla.com/D268464

Diffstat:
M
dom/media/MediaDecoder.cpp
 | 
14
++++++++------
M
dom/media/MediaDecoder.h
 | 
3
++-

2 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/dom/media/MediaDecoder.cpp b/dom/media/MediaDecoder.cpp
@@ -381,7 +381,7 @@ void MediaDecoder::OnPlaybackErrorEvent(const MediaResult& aError) {
 #ifdef MOZ_WMF_MEDIA_ENGINE
   if (aError == NS_ERROR_DOM_MEDIA_EXTERNAL_ENGINE_NOT_SUPPORTED_ERR ||
       aError == NS_ERROR_DOM_MEDIA_CDM_PROXY_NOT_SUPPORTED_ERR) {
-    SwitchStateMachine(aError);
+    Unused << SwitchStateMachine(aError);
     return;
   }
 #endif
@@ -389,12 +389,12 @@ void MediaDecoder::OnPlaybackErrorEvent(const MediaResult& aError) {
 }
 
 #ifdef MOZ_WMF_MEDIA_ENGINE
-void MediaDecoder::SwitchStateMachine(const MediaResult& aError) {
+bool MediaDecoder::SwitchStateMachine(const MediaResult& aError) {
   MOZ_ASSERT(aError == NS_ERROR_DOM_MEDIA_EXTERNAL_ENGINE_NOT_SUPPORTED_ERR ||
              aError == NS_ERROR_DOM_MEDIA_CDM_PROXY_NOT_SUPPORTED_ERR);
   // Already in shutting down decoder, no need to create another state machine.
   if (mPlayState == PLAY_STATE_SHUTDOWN) {
-    return;
+    return false;
   }
 
   // External engine can't play the resource or we intentionally disable it, try
@@ -473,6 +473,7 @@ void MediaDecoder::SwitchStateMachine(const MediaResult& aError) {
 
   discardStateMachine->BeginShutdown()->Then(
       AbstractThread::MainThread(), __func__, [discardStateMachine] {});
+  return true;
 }
 #endif
 
@@ -1513,12 +1514,13 @@ RefPtr<SetCDMPromise> MediaDecoder::SetCDMProxy(CDMProxy* aProxy) {
       // given CDM proxy.
       LOG("CDM proxy %s not supported! Switch to another state machine.",
           NS_ConvertUTF16toUTF8(aProxy->KeySystem()).get());
-      SwitchStateMachine(
+      bool switched = SwitchStateMachine(
           MediaResult{NS_ERROR_DOM_MEDIA_CDM_PROXY_NOT_SUPPORTED_ERR, aProxy});
       rv = GetStateMachine()->IsCDMProxySupported(aProxy);
       if (NS_FAILED(rv)) {
-        MOZ_DIAGNOSTIC_CRASH("CDM proxy not supported after switch!");
-        LOG("CDM proxy not supported after switch!");
+        MOZ_DIAGNOSTIC_ASSERT(
+            !switched, "We should only reach here if we failed to switch");
+        LOG("CDM proxy is still not supported!");
         return SetCDMPromise::CreateAndReject(rv, __func__);
       }
     }
diff --git a/dom/media/MediaDecoder.h b/dom/media/MediaDecoder.h
@@ -565,7 +565,8 @@ class MediaDecoder : public DecoderDoctorLifeLogger<MediaDecoder> {
   void ConnectMirrors(MediaDecoderStateMachineBase* aObject);
   void DisconnectMirrors();
 #  ifdef MOZ_WMF_MEDIA_ENGINE
-  void SwitchStateMachine(const MediaResult& aError);
+  // Return true if we switched to a new state machine.
+  bool SwitchStateMachine(const MediaResult& aError);
 #  endif
 
   virtual bool CanPlayThroughImpl() = 0;