dom/media/CallbackThreadRegistry.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef CALLBACKTHREADREGISTRY_H
   8 #define CALLBACKTHREADREGISTRY_H
   9
  10 #include <cstdint>
  11 #include <mozilla/DataMutex.h>
  12 #include <nsTArray.h>
  13 #include <thread>
  14 #include <GeckoProfiler.h>
  15
  16 namespace mozilla {
  17
  18 // This class is a singleton that tracks various callback threads and makes
  19 // sure they are registered or unregistered to the profiler safely and
  20 // consistently.
  21 //
  22 // Register and Unregister are fairly expensive and shouldn't be used in a hot
  23 // path.
  24 class CallbackThreadRegistry final {
  25  public:
  26   CallbackThreadRegistry();
  27
  28   ~CallbackThreadRegistry() {
  29     // It would be nice to be able to assert that all threads have been
  30     // unregistered, but we can't: it's legal to suspend an audio stream, so
  31     // that the callback isn't called, and then immediately destroy it.
  32   }
  33
  34   CallbackThreadRegistry(const CallbackThreadRegistry&) = delete;
  35   CallbackThreadRegistry& operator=(const CallbackThreadRegistry&) = delete;
  36   CallbackThreadRegistry(CallbackThreadRegistry&&) = delete;
  37   CallbackThreadRegistry& operator=(CallbackThreadRegistry&&) = delete;
  38
  39   // Returns the global instance of CallbackThreadRegistry. Safe from all
  40   // threads.
  41   static CallbackThreadRegistry* Get();
  42
  43   // This is intended to be called in the first callback of a callback
  44   // thread.
  45   void Register(ProfilerThreadId aThreadId, const char* aName);
  46
  47   // This is intended to be called when an object stops an audio callback thread
  48   void Unregister(ProfilerThreadId aThreadId);
  49
  50  private:
  51   struct ThreadUserCount {
  52     ProfilerThreadId mId;  // from profiler_current_thread_id
  53     int mUserCount = 0;
  54   };
  55   DataMutex<nsTArray<ThreadUserCount>> mThreadIds;
  56 };
  57
  58 }  // namespace mozilla
  59
  60 #endif  // CALLBACKTHREADREGISTRY_H