Don't drop the GPUProcess media assertion too promptly after playback…

… ends

https://bugs.webkit.org/show_bug.cgi?id=259219
rdar://112003621

Reviewed by Jer Noble and Eric Carlson.

Don't drop the GPUProcess media assertion too promptly after playback ends,
instead, drop it on a timer.

There is a race where both the GPUProcess and the UIProcess get notified of a
WebProcess exiting in parallel. When notified, the UIProcess would drop the
media assertion on the GPUProcess, which could get it to suspend while the
GPUProcess is STILL shutting down the media stack.

Dropping the media assertion on a timer makes it so that the GPUProcess is now
extremely unlikely to lose the race and will have properly shut down the media
stack by the time it gets suspended.

* Source/WebKit/UIProcess/WebProcessPool.cpp:
(WebKit::WebProcessPool::clearAudibleActivity):
(WebKit::WebProcessPool::updateAudibleMediaAssertions):
* Source/WebKit/UIProcess/WebProcessPool.h:

Canonical link: https://commits.webkit.org/266069@main

Source/WebKit/UIProcess/WebProcessPool.cpp

@@ -166,6 +166,8 @@ constexpr unsigned maximumGPUProcessRelaunchAttemptsBeforeKillingWebProcesses {
 bool WebProcessPool::s_shouldCrashWhenCreatingWebProcess = false;
 #endif
 
+static constexpr Seconds audibleActivityClearDelay = 5_s;
+
 bool WebProcessPool::s_didGlobalStaticInitialization = false;
 
 Ref<WebProcessPool> WebProcessPool::create(API::ProcessPoolConfiguration& configuration)
@@ -233,6 +235,7 @@ WebProcessPool::WebProcessPool(API::ProcessPoolConfiguration& configuration)
     , m_backForwardCache(makeUniqueRef<WebBackForwardCache>(*this))
     , m_webProcessCache(makeUniqueRef<WebProcessCache>(*this))
     , m_webProcessWithAudibleMediaCounter([this](RefCounterEvent) { updateAudibleMediaAssertions(); })
+    , m_audibleActivityTimer(RunLoop::main(), this, &WebProcessPool::clearAudibleActivity)
     , m_webProcessWithMediaStreamingCounter([this](RefCounterEvent) { updateMediaStreamingActivity(); })
 {
     if (!s_didGlobalStaticInitialization) {
@@ -2156,14 +2159,24 @@ WebProcessWithAudibleMediaToken WebProcessPool::webProcessWithAudibleMediaToken(
     return m_webProcessWithAudibleMediaCounter.count();
 }
 
+void WebProcessPool::clearAudibleActivity()
+{
+    ASSERT(!m_webProcessWithAudibleMediaCounter.value());
+    m_audibleMediaActivity = std::nullopt;
+}
+
 void WebProcessPool::updateAudibleMediaAssertions()
 {
     if (!m_webProcessWithAudibleMediaCounter.value()) {
         WEBPROCESSPOOL_RELEASE_LOG(ProcessSuspension, "updateAudibleMediaAssertions: The number of processes playing audible media now zero. Releasing UI process assertion.");
-        m_audibleMediaActivity = std::nullopt;
+        // We clear the audible activity on a timer for 2 reasons:
+        // 1. Media may start playing shortly after (e.g. switching from one track to another)
+        // 2. It minimizes the risk of the GPUProcess getting suspended while shutting down the media stack.
+        m_audibleActivityTimer.startOneShot(audibleActivityClearDelay);
         return;
     }
 
+    m_audibleActivityTimer.stop();
     if (m_audibleMediaActivity)
         return;
 

Source/WebKit/UIProcess/WebProcessPool.h

@@ -631,6 +631,7 @@ class WebProcessPool final
 #if HAVE(MEDIA_ACCESSIBILITY_FRAMEWORK)
     void setMediaAccessibilityPreferences(WebProcessProxy&);
 #endif
+    void clearAudibleActivity();
 
     Ref<API::ProcessPoolConfiguration> m_configuration;
 
@@ -803,6 +804,7 @@ class WebProcessPool final
 #endif
     };
     std::optional<AudibleMediaActivity> m_audibleMediaActivity;
+    RunLoop::Timer m_audibleActivityTimer;
 
     WebProcessWithMediaStreamingCounter m_webProcessWithMediaStreamingCounter;
     bool m_mediaStreamingActivity { false };