Regression(r279601) ProcessAssertion may get destroyed on a backgroun…

…d thread

https://bugs.webkit.org/show_bug.cgi?id=227875
<rdar://76972252>

Reviewed by Geoffrey Garen.

r279601 added an internal WorkQueue to ProcessAssertion, so that we could acquire the RunningBoard assertion
asynchronously on the background queue. When dispatching to the background queue, we capture |protectedThis|,
which means that ProcessAssertion may now get destroyed on the background queue. To address the isuse, we
now make sure to dispatch |protectedThis| back to the main thread in acquireAsync().

* UIProcess/ios/ProcessAssertionIOS.mm:
(WebKit::ProcessAssertion::acquireAsync):


Canonical link: https://commits.webkit.org/239630@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@279877 268f45cc-cd09-0410-ab3c-d52691b4dbfc

Source/WebKit/ChangeLog

@@ -1,3 +1,19 @@
+2021-07-13  Chris Dumez  <cdumez@apple.com>
+
+        Regression(r279601) ProcessAssertion may get destroyed on a background thread
+        https://bugs.webkit.org/show_bug.cgi?id=227875
+        <rdar://76972252>
+
+        Reviewed by Geoffrey Garen.
+
+        r279601 added an internal WorkQueue to ProcessAssertion, so that we could acquire the RunningBoard assertion
+        asynchronously on the background queue. When dispatching to the background queue, we capture |protectedThis|,
+        which means that ProcessAssertion may now get destroyed on the background queue. To address the isuse, we
+        now make sure to dispatch |protectedThis| back to the main thread in acquireAsync().
+
+        * UIProcess/ios/ProcessAssertionIOS.mm:
+        (WebKit::ProcessAssertion::acquireAsync):
+
 2021-07-13  Kate Cheney  <katherine_cheney@apple.com>
 
         Allow layout tests to specify app initiated loads or not

Source/WebKit/UIProcess/ios/ProcessAssertionIOS.mm

@@ -343,10 +343,14 @@ - (void)assertion:(RBSAssertion *)assertion didInvalidateWithError:(NSError *)er
 
 void ProcessAssertion::acquireAsync(CompletionHandler<void()>&& completionHandler)
 {
+    ASSERT(isMainRunLoop());
     assertionsWorkQueue().dispatch([protectedThis = makeRef(*this), completionHandler = WTFMove(completionHandler)]() mutable {
         protectedThis->acquireSync();
-        if (completionHandler)
-            RunLoop::main().dispatch(WTFMove(completionHandler));
+        if (completionHandler) {
+            RunLoop::main().dispatch([protectedThis = WTFMove(protectedThis), completionHandler = WTFMove(completionHandler)]() mutable {
+                completionHandler();
+            });
+        }
     });
 }