Bug 1640835 - Bail out early from InputQueue::MainThreadTimeout if sControllerThread has been already discarded. r=botond

Differential Revision: https://phabricator.services.mozilla.com/D85335

gfx/layers/apz/src/InputQueue.cpp

@@ -677,6 +677,11 @@ InputBlockState* InputQueue::FindBlockForId(uint64_t aInputBlockId,
 }
 
 void InputQueue::MainThreadTimeout(uint64_t aInputBlockId) {
+  // It's possible that this function gets called after the controller thread
+  // was discarded during shutdown.
+  if (!APZThreadUtils::IsControllerThreadAlive()) {
+    return;
+  }
   APZThreadUtils::AssertOnControllerThread();
 
   INPQ_LOG("got a main thread timeout; block=%" PRIu64 "\n", aInputBlockId);

gfx/layers/apz/util/APZThreadUtils.cpp

@@ -84,6 +84,12 @@ bool APZThreadUtils::IsControllerThread() {
   return sControllerThread && sControllerThread->IsOnCurrentThread();
 }
 
+/*static*/
+bool APZThreadUtils::IsControllerThreadAlive() {
+  StaticMutexAutoLock lock(sControllerThreadMutex);
+  return !!sControllerThread;
+}
+
 /*static*/
 void APZThreadUtils::DelayedDispatch(already_AddRefed<Runnable> aRunnable,
                                      int aDelayMs) {

gfx/layers/apz/util/APZThreadUtils.h

@@ -53,6 +53,11 @@ class APZThreadUtils {
    */
   static bool IsControllerThread();
 
+  /**
+   * Returns true if the controller thread is still alive.
+   */
+  static bool IsControllerThreadAlive();
+
   /**
    * Schedules a runnable to run on the controller thread at some time
    * in the future.