gistfile0.txt

commit aa4ab75f13ad4882c25ab77997c907d2b374c39b
Author: Yoshi Cheng-Hao Huang <allstars.chh@gmail.com>
Date:   Fri Jan 8 15:50:42 2021 +0100

    submit a task to TaskController during XPCOMShutdown.

diff --git a/xpcom/build/XPCOMInit.cpp b/xpcom/build/XPCOMInit.cpp
index 9fd9fb255e41..baaa97753681 100644
--- a/xpcom/build/XPCOMInit.cpp
+++ b/xpcom/build/XPCOMInit.cpp
@@ -572,16 +572,24 @@ void SetICUMemoryFunctions() {
     if (!JS_SetICUMemoryFunctions(ICUReporter::Alloc, ICUReporter::Realloc,
                                   ICUReporter::Free)) {
       MOZ_CRASH("JS_SetICUMemoryFunctions failed.");
     }
     sICUReporterInitialized = true;
   }
 }
 
+class DummyTask : public Task {
+ public:
+  explicit DummyTask() : Task(false, EventQueuePriority::Normal) {}
+  bool Run() override {
+    return true;
+  }
+};
+
 nsresult ShutdownXPCOM(nsIServiceManager* aServMgr) {
   // Make sure the hang monitor is enabled for shutdown.
   BackgroundHangMonitor().NotifyActivity();
 
   if (!NS_IsMainThread()) {
     MOZ_CRASH("Shutdown on wrong thread");
   }
 
@@ -733,16 +741,18 @@ nsresult ShutdownXPCOM(nsIServiceManager* aServMgr) {
   } else {
     NS_WARNING("Component Manager was never created ...");
   }
 
   if (sInitializedJS) {
     // Shut down the JS engine.
     JS_ShutDown();
     sInitializedJS = false;
+
+    TaskController::Get()->AddTask(MakeAndAddRef<DummyTask>());
   }
 
   // After all threads have been joined and the component manager has been shut
   // down, any remaining objects that could be holding NSS resources (should)
   // have been released, so we can safely shut down NSS.
   if (NSS_IsInitialized()) {
     nsNSSComponent::DoClearSSLExternalAndInternalSessionCache();
     if (NSS_Shutdown() != SECSuccess) {
diff --git a/xpcom/threads/TaskController.cpp b/xpcom/threads/TaskController.cpp
index da41135c32d4..7409bdee7f3d 100644
--- a/xpcom/threads/TaskController.cpp
+++ b/xpcom/threads/TaskController.cpp
@@ -206,16 +206,17 @@ void TaskController::RunPoolThread() {
   threadName.AppendLiteral("TaskController Thread #");
   threadName.AppendInt(static_cast<int64_t>(mThreadPoolIndex));
   PROFILER_REGISTER_THREAD(threadName.BeginReading());
 
   MutexAutoLock lock(mGraphMutex);
   while (true) {
     if (mShuttingDown) {
       IOInterposer::UnregisterCurrentThread();
+      MOZ_ASSERT(mThreadableTasks.empty());
       return;
     }
     bool ranTask = false;
 
     if (!mThreadableTasks.empty()) {
       for (auto iter = mThreadableTasks.begin(); iter != mThreadableTasks.end();
            ++iter) {
         // Search for the highest priority dependency of the highest priority