Changeset 269934 in webkit

Timestamp:

Nov 17, 2020 4:36:12 PM (3 years ago)

Author:

Chris Dumez

Message:

Make sure ProcessThrottler is always holding a ProcessAssertion for its child process
​https://bugs.webkit.org/show_bug.cgi?id=219053

Reviewed by Geoff Garen.

Make sure ProcessThrottler is always holding a ProcessAssertion for its child process. Previously, when changing the assertion
type (e.g. when going from background to foreground) we would release the previous assertion and then take the new one.

RunningBoard developers recommend that we wait until the new ProcessAssertion is taken before we release the previous one to
avoid churn. It is also important we always hold a ProcessAssertion at all times for the child process because the child process
may exit otherwise.

• UIProcess/ProcessThrottler.cpp:

(WebKit::ProcessThrottler::setAssertionType):

Location:

trunk/Source/WebKit

Files:

• ChangeLog (modified) (1 diff)
• UIProcess/ProcessThrottler.cpp (modified) (1 diff)

trunk/Source/WebKit/ChangeLog

@@ +1 @@
+2020-11-17  Chris Dumez  <cdumez@apple.com>
+
+        Make sure ProcessThrottler is always holding a ProcessAssertion for its child process
+        https://bugs.webkit.org/show_bug.cgi?id=219053
+
+        Reviewed by Geoff Garen.
+
+        Make sure ProcessThrottler is always holding a ProcessAssertion for its child process. Previously, when changing the assertion
+        type (e.g. when going from background to foreground) we would release the previous assertion and then take the new one.
+
+        RunningBoard developers recommend that we wait until the new ProcessAssertion is taken before we release the previous one to
+        avoid churn. It is also important we always hold a ProcessAssertion at all times for the child process because the child process
+        may exit otherwise.
+
+        * UIProcess/ProcessThrottler.cpp:
+        (WebKit::ProcessThrottler::setAssertionType):
+
 2020-11-17  Chris Dumez  <cdumez@apple.com>
 

trunk/Source/WebKit/UIProcess/ProcessThrottler.cpp

@@ -128 +128 @@
 
     PROCESSTHROTTLER_RELEASE_LOG("setAssertionType: Updating process assertion type to %u (foregroundActivities: %u, backgroundActivities: %u)", newType, m_foregroundActivities.size(), m_backgroundActivities.size());
+
+    // Keep the previous assertion around until after the new one has been created so that we always hold
+    // a process assertion for the process.
+    auto previousAssertion = std::exchange(m_assertion, nullptr);
     if (m_shouldTakeUIBackgroundAssertion) {
         auto assertion = makeUnique<ProcessAndUIAssertion>(m_processIdentifier, assertionName(newType), newType);