Title: [284644] trunk/Source/WebKit
- Revision
- 284644
- Author
- simon.fra...@apple.com
- Date
- 2021-10-21 14:33:01 -0700 (Thu, 21 Oct 2021)
Log Message
Rare crash under DisplayLink::displayLinkCallback()
https://bugs.webkit.org/show_bug.cgi?id=232101
<rdar://84153991>
Reviewed by Tim Horton.
The crash was a divide by zero under m_currentUpdate.nextUpdate(), indicating that
m_currentUpdate.updatesPerSecond was zero. Previous assumptions that this was caused
by weird display configs were wrong. The actual issue is a race condition where
the callback can fire while we're still inside CVDisplayLinkStart(), or at least
before we've updated m_currentUpdate.
The fix is to initialize m_currentUpdate before we call CVDisplayLinkStart().
* UIProcess/mac/DisplayLink.cpp:
(WebKit::DisplayLink::addObserver):
Modified Paths
Diff
Modified: trunk/Source/WebKit/ChangeLog (284643 => 284644)
--- trunk/Source/WebKit/ChangeLog 2021-10-21 21:22:09 UTC (rev 284643)
+++ trunk/Source/WebKit/ChangeLog 2021-10-21 21:33:01 UTC (rev 284644)
@@ -1,3 +1,22 @@
+2021-10-21 Simon Fraser <simon.fra...@apple.com>
+
+ Rare crash under DisplayLink::displayLinkCallback()
+ https://bugs.webkit.org/show_bug.cgi?id=232101
+ <rdar://84153991>
+
+ Reviewed by Tim Horton.
+
+ The crash was a divide by zero under m_currentUpdate.nextUpdate(), indicating that
+ m_currentUpdate.updatesPerSecond was zero. Previous assumptions that this was caused
+ by weird display configs were wrong. The actual issue is a race condition where
+ the callback can fire while we're still inside CVDisplayLinkStart(), or at least
+ before we've updated m_currentUpdate.
+
+ The fix is to initialize m_currentUpdate before we call CVDisplayLinkStart().
+
+ * UIProcess/mac/DisplayLink.cpp:
+ (WebKit::DisplayLink::addObserver):
+
2021-10-21 Per Arne Vollan <pvol...@apple.com>
Launch Services database is not always sent to GPUP
Modified: trunk/Source/WebKit/UIProcess/mac/DisplayLink.cpp (284643 => 284644)
--- trunk/Source/WebKit/UIProcess/mac/DisplayLink.cpp 2021-10-21 21:22:09 UTC (rev 284643)
+++ trunk/Source/WebKit/UIProcess/mac/DisplayLink.cpp 2021-10-21 21:33:01 UTC (rev 284644)
@@ -101,16 +101,12 @@
if (!CVDisplayLinkIsRunning(m_displayLink)) {
LOG_WITH_STREAM(DisplayLink, stream << "[UI ] DisplayLink for display " << m_displayID << " starting CVDisplayLink with fps " << m_displayNominalFramesPerSecond);
+
+ m_currentUpdate = { 0, m_displayNominalFramesPerSecond };
+
CVReturn error = CVDisplayLinkStart(m_displayLink);
if (error)
RELEASE_LOG_FAULT(DisplayLink, "DisplayLink: Could not start the display link: %d", error);
-
- if (!m_displayNominalFramesPerSecond) {
- RELEASE_LOG_FAULT(DisplayLink, "DisplayLink: displayNominalFramesPerSecond is 0, using %d", WebCore::FullSpeedFramesPerSecond);
- m_displayNominalFramesPerSecond = WebCore::FullSpeedFramesPerSecond;
- };
-
- m_currentUpdate = { 0, m_displayNominalFramesPerSecond };
}
}
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