diff --git a/test/time_controller/simulated_time_controller.cc b/test/time_controller/simulated_time_controller.cc
index a81083b..769be3f 100644
--- a/test/time_controller/simulated_time_controller.cc
+++ b/test/time_controller/simulated_time_controller.cc
@@ -57,7 +57,6 @@
 
 std::unique_ptr<ProcessThread> SimulatedTimeControllerImpl::CreateProcessThread(
     const char* thread_name) {
-  rtc::CritScope lock(&lock_);
   auto process_thread =
       std::make_unique<SimulatedProcessThread>(this, thread_name);
   Register(process_thread.get());
@@ -117,10 +116,12 @@
     while (!ready_runners_.empty()) {
       auto* runner = ready_runners_.front();
       ready_runners_.pop_front();
+      lock_.Leave();
       // Note that the RunReady function might indirectly cause a call to
-      // Unregister() which will recursively grab |lock_| again to remove items
-      // from |ready_runners_|.
+      // Unregister() which will grab |lock_| again to remove items from
+      // |ready_runners_|.
       runner->RunReady(current_time);
+      lock_.Enter();
     }
   }
 }
@@ -169,6 +170,7 @@
 void SimulatedTimeControllerImpl::StopYield(TaskQueueBase* yielding_from) {
   yielded_.erase(yielding_from);
 }
+
 }  // namespace sim_time_impl
 
 GlobalSimulatedTimeController::GlobalSimulatedTimeController(
diff --git a/test/time_controller/simulated_time_controller.h b/test/time_controller/simulated_time_controller.h
index 758f909..48112b3 100644
--- a/test/time_controller/simulated_time_controller.h
+++ b/test/time_controller/simulated_time_controller.h
@@ -52,32 +52,34 @@
 
   std::unique_ptr<TaskQueueBase, TaskQueueDeleter> CreateTaskQueue(
       absl::string_view name,
-      Priority priority) const override;
+      Priority priority) const RTC_LOCKS_EXCLUDED(time_lock_) override;
 
   // Implements the YieldInterface by running ready tasks on all task queues,
   // except that if this method is called from a task, the task queue running
   // that task is skipped.
-  void YieldExecution() override;
+  void YieldExecution() RTC_LOCKS_EXCLUDED(time_lock_, lock_) override;
   // Create process thread with the name |thread_name|.
-  std::unique_ptr<ProcessThread> CreateProcessThread(const char* thread_name);
+  std::unique_ptr<ProcessThread> CreateProcessThread(const char* thread_name)
+      RTC_LOCKS_EXCLUDED(time_lock_, lock_);
   // Create thread using provided |socket_server|.
   std::unique_ptr<rtc::Thread> CreateThread(
       const std::string& name,
-      std::unique_ptr<rtc::SocketServer> socket_server);
+      std::unique_ptr<rtc::SocketServer> socket_server)
+      RTC_LOCKS_EXCLUDED(time_lock_, lock_);
 
   // Runs all runners in |runners_| that has tasks or modules ready for
   // execution.
-  void RunReadyRunners();
+  void RunReadyRunners() RTC_LOCKS_EXCLUDED(time_lock_, lock_);
   // Return |current_time_|.
-  Timestamp CurrentTime() const;
+  Timestamp CurrentTime() const RTC_LOCKS_EXCLUDED(time_lock_);
   // Return min of runner->GetNextRunTime() for runner in |runners_|.
-  Timestamp NextRunTime() const;
+  Timestamp NextRunTime() const RTC_LOCKS_EXCLUDED(lock_);
   // Set |current_time_| to |target_time|.
-  void AdvanceTime(Timestamp target_time);
+  void AdvanceTime(Timestamp target_time) RTC_LOCKS_EXCLUDED(time_lock_);
   // Adds |runner| to |runners_|.
-  void Register(SimulatedSequenceRunner* runner);
+  void Register(SimulatedSequenceRunner* runner) RTC_LOCKS_EXCLUDED(lock_);
   // Removes |runner| from |runners_|.
-  void Unregister(SimulatedSequenceRunner* runner);
+  void Unregister(SimulatedSequenceRunner* runner) RTC_LOCKS_EXCLUDED(lock_);
 
   // Indicates that |yielding_from| is not ready to run.
   void StartYield(TaskQueueBase* yielding_from);