tor-browser

commit 23646486fcef58b80fc17c4da540f58795821aa3
parent b1f784aebbf90355fb6d522828211c7da836fbab
Author: Karl Tomlinson <karlt+@karlt.net>
Date:   Wed,  8 Oct 2025 04:50:53 +0000

Bug 1992922 wait for target time before, rather than after, each ThreadedDriver iteration r=padenot

When switching from AudioCallbackDriver, this will allow, in a subsequent
patch, the SystemClockDriver to time its first iteration appropriately.

When switching to AudioCallbackDriver, this allows the audio thread to be
started up to 10ms faster.

Differential Revision: https://phabricator.services.mozilla.com/D267737

Diffstat:
M
dom/media/GraphDriver.cpp
 | 
3
++-
M
dom/media/GraphDriver.h
 | 
7
++++++-

2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/dom/media/GraphDriver.cpp b/dom/media/GraphDriver.cpp
@@ -187,6 +187,8 @@ SystemClockDriver::~SystemClockDriver() = default;
 void ThreadedDriver::RunThread() {
   mThreadRunning = true;
   while (true) {
+    WaitForNextIteration();
+
     MediaTime interval = GetIntervalForIteration();
     auto iterationStart = mIterationEnd;
     mIterationEnd += interval;
@@ -212,7 +214,6 @@ void ThreadedDriver::RunThread() {
       result.Stopped();
       break;
     }
-    WaitForNextIteration();
     if (GraphDriver* nextDriver = result.NextDriver()) {
       LOG(LogLevel::Debug, ("%p: Switching to AudioCallbackDriver", Graph()));
       result.Switched();
diff --git a/dom/media/GraphDriver.h b/dom/media/GraphDriver.h
@@ -367,7 +367,12 @@ class ThreadedDriver : public GraphDriver {
   class IterationWaitHelper {
     Monitor mMonitor MOZ_UNANNOTATED;
     // The below members are guarded by mMonitor.
-    bool mNeedAnotherIteration = false;
+
+    // Whether another iteration is required either to process control
+    // messages or to render.
+    // Drivers do not pass on this state when switching to another driver,
+    // so always perform at least one iteration.
+    bool mNeedAnotherIteration = true;
     TimeStamp mWakeTime;
 
    public: