Changeset 110699 in webkit

Timestamp:

Mar 14, 2012 8:02:14 AM (12 years ago)

Author:

abecsi@webkit.org

Message:

[Qt] RunLoopQt is missing reentrancy guards
​https://bugs.webkit.org/show_bug.cgi?id=80982

Patch by Simon Hausmann <​simon.hausmann@nokia.com> on 2012-03-14
Reviewed by Tor Arne Vestbø.

Avoid recursive calls to RunLoop::performWork() with a simple
counting mechanism, to avoid out-of-order message dispatching.

• platform/qt/RunLoopQt.cpp:

(WebCore::RunLoop::TimerObject::TimerObject):
(WebCore::RunLoop::TimerObject::performWork):
(RunLoop::TimerObject):

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/qt/RunLoopQt.cpp (modified) (3 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2012-03-14  Simon Hausmann  <simon.hausmann@nokia.com>
+
+        [Qt] RunLoopQt is missing reentrancy guards
+        https://bugs.webkit.org/show_bug.cgi?id=80982
+
+        Reviewed by Tor Arne Vestbø.
+
+        Avoid recursive calls to RunLoop::performWork() with a simple
+        counting mechanism, to avoid out-of-order message dispatching.
+
+        * platform/qt/RunLoopQt.cpp:
+        (WebCore::RunLoop::TimerObject::TimerObject):
+        (WebCore::RunLoop::TimerObject::performWork):
+        (RunLoop::TimerObject):
+
 2012-03-14  Ilya Tikhonovsky  <loislo@chromium.org>
 

trunk/Source/WebCore/platform/qt/RunLoopQt.cpp

@@ -40 +40 @@
     Q_OBJECT
 public:
-    TimerObject(RunLoop* runLoop) : m_runLoop(runLoop)
+    TimerObject(RunLoop* runLoop)
+        : m_runLoop(runLoop)
+        , m_pendingPerformWorkInvocations(0)
     {
         int methodIndex = metaObject()->indexOfMethod("performWork()");
@@ -46 +48 @@
     }
 
-    Q_SLOT void performWork() { m_runLoop->performWork(); }
+    Q_SLOT void performWork() {
+        // It may happen that a secondary thread adds more method invocations via
+        // RunLoop::dispatch(), which will schedule a call to this function. If during
+        // performWork() event loop messages get processed, it may happen that this
+        // function is called again. In this case we should protected ourselves against
+        // recursive - and thus out-of-order - message dispatching and instead perform
+        // the work serially.
+        m_pendingPerformWorkInvocations++;
+        if (m_pendingPerformWorkInvocations > 1)
+            return;
+
+        while (m_pendingPerformWorkInvocations) {
+            m_runLoop->performWork();
+            m_pendingPerformWorkInvocations--;
+        }
+    }
     inline void wakeUp() { m_method.invoke(this, Qt::QueuedConnection); }
 
@@ -58 +75 @@
     RunLoop* m_runLoop;
     QMetaMethod m_method;
+    int m_pendingPerformWorkInvocations;
 };