1 files changed, 60 insertions, 0 deletions
diff --git a/dom/media/CallbackThreadRegistry.h b/dom/media/CallbackThreadRegistry.h
new file mode 100644
index 0000000000..a154b3a35f
--- /dev/null
+++ b/dom/media/CallbackThreadRegistry.h
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef CALLBACKTHREADREGISTRY_H
+#define CALLBACKTHREADREGISTRY_H
+
+#include <cstdint>
+#include <mozilla/DataMutex.h>
+#include <nsTArray.h>
+#include <thread>
+#include <GeckoProfiler.h>
+
+namespace mozilla {
+
+// This class is a singleton that tracks various callback threads and makes
+// sure they are registered or unregistered to the profiler safely and
+// consistently.
+//
+// Register and Unregister are fairly expensive and shouldn't be used in a hot
+// path.
+class CallbackThreadRegistry final {
+ public:
+  CallbackThreadRegistry();
+
+  ~CallbackThreadRegistry() {
+    // It would be nice to be able to assert that all threads have been
+    // unregistered, but we can't: it's legal to suspend an audio stream, so
+    // that the callback isn't called, and then immediately destroy it.
+  }
+
+  CallbackThreadRegistry(const CallbackThreadRegistry&) = delete;
+  CallbackThreadRegistry& operator=(const CallbackThreadRegistry&) = delete;
+  CallbackThreadRegistry(CallbackThreadRegistry&&) = delete;
+  CallbackThreadRegistry& operator=(CallbackThreadRegistry&&) = delete;
+
+  // Returns the global instance of CallbackThreadRegistry. Safe from all
+  // threads.
+  static CallbackThreadRegistry* Get();
+
+  // This is intended to be called in the first callback of a callback
+  // thread.
+  void Register(ProfilerThreadId aThreadId, const char* aName);
+
+  // This is intended to be called when an object stops an audio callback thread
+  void Unregister(ProfilerThreadId aThreadId);
+
+ private:
+  struct ThreadUserCount {
+    ProfilerThreadId mId;  // from profiler_current_thread_id
+    int mUserCount = 0;
+  };
+  DataMutex<nsTArray<ThreadUserCount>> mThreadIds;
+};
+
+}  // namespace mozilla
+
+#endif  // CALLBACKTHREADREGISTRY_H