Attachment 368490 Details for Bug 197385 – Patch

[patch] Patch

bug-197385-20190429140316.patch (text/plain), 4.19 KB, created by Chris Dumez on 2019-04-29 14:03:16 PDT

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Creator: Chris Dumez

Created: 2019-04-29 14:03:16 PDT

Size: 4.19 KB

patch

obsolete

>Subversion Revision: 244735
>diff --git a/Source/WebKit/ChangeLog b/Source/WebKit/ChangeLog
>index 00b570606c3997e50d17e73e5972ca4bb24b902e..d32e45e0f8b28e0296bc1def78e2ff9097b73cad 100644
>--- a/Source/WebKit/ChangeLog
>+++ b/Source/WebKit/ChangeLog
>@@ -1,3 +1,25 @@
>+2019-04-29  Chris Dumez  <cdumez@apple.com>
>+
>+        [iOS] The UIProcess may get killed for trying to stay runnable in the background for more than 30 seconds
>+        https://bugs.webkit.org/show_bug.cgi?id=197385
>+        <rdar://problem/50001505>
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        If the UIProcess holds a background assertion for itself for 30 seconds, the assertion's invalidation handler
>+        will get called and it is our responsibility to release this assertion or the UIProcess will get killed by the
>+        system. The logic in ProcessAssertion would normally do that but it would also happily try and re-take another
>+        background process assertion shortly after the previous one expired (and before the UIProcess got suspended).
>+        When doing so, the new background assertion would expire right away and we would get killed without its
>+        invalidation handler getting called.
>+
>+        To address the issue, the logic in ProcessAssertion will now prevent taking a new background assertion after
>+        one expires and until the application becomes foreground again.
>+
>+        * UIProcess/ios/ProcessAssertionIOS.mm:
>+        (-[WKProcessAssertionBackgroundTaskManager init]):
>+        (-[WKProcessAssertionBackgroundTaskManager _updateBackgroundTask]):
>+
> 2019-04-29  Alex Christensen  <achristensen@webkit.org>
> 
>         Build fix.
>diff --git a/Source/WebKit/UIProcess/ios/ProcessAssertionIOS.mm b/Source/WebKit/UIProcess/ios/ProcessAssertionIOS.mm
>index 0c9adf3f5c13929d160ef44ac09acf27242bcbdf..8aa2dcf04c346e032443d1f9a20334af2224fcac 100644
>--- a/Source/WebKit/UIProcess/ios/ProcessAssertionIOS.mm
>+++ b/Source/WebKit/UIProcess/ios/ProcessAssertionIOS.mm
>@@ -50,6 +50,7 @@ @implementation WKProcessAssertionBackgroundTaskManager
> {
>     UIBackgroundTaskIdentifier _backgroundTask;
>     HashSet<ProcessAndUIAssertion*> _assertionsNeedingBackgroundTask;
>+    BOOL _assertionHasExpiredInTheBackground;
> }
> 
> + (WKProcessAssertionBackgroundTaskManager *)shared
>@@ -66,6 +67,11 @@ - (instancetype)init
> 
>     _backgroundTask = UIBackgroundTaskInvalid;
> 
>+    [[NSNotificationCenter defaultCenter] addObserverForName:UIApplicationWillEnterForegroundNotification object:[UIApplication sharedApplication] queue:nil usingBlock:^(NSNotification *) {
>+        _assertionHasExpiredInTheBackground = NO;
>+        [self _updateBackgroundTask];
>+    }];
>+
>     return self;
> }
> 
>@@ -98,6 +104,11 @@ - (void)_notifyAssertionsOfImminentSuspension
> - (void)_updateBackgroundTask
> {
>     if (!_assertionsNeedingBackgroundTask.isEmpty() && _backgroundTask == UIBackgroundTaskInvalid) {
>+        if (_assertionHasExpiredInTheBackground) {
>+            RELEASE_LOG_ERROR(ProcessSuspension, "%p - WKProcessAssertionBackgroundTaskManager: Ignored request to start a background task because we're still in the background and the previous task expired", self);
>+            // Our invalidation handler would not get called if we tried to re-take a new background assertion at this point, and the UIProcess would get killed (rdar://problem/50001505).
>+            return;
>+        }
>         RELEASE_LOG(ProcessSuspension, "%p - WKProcessAssertionBackgroundTaskManager - beginBackgroundTaskWithName", self);
>         _backgroundTask = [[UIApplication sharedApplication] beginBackgroundTaskWithName:@"com.apple.WebKit.ProcessAssertion" expirationHandler:^{
>             RELEASE_LOG_ERROR(ProcessSuspension, "Background task expired while holding WebKit ProcessAssertion (isMainThread? %d).", RunLoop::isMain());
>@@ -109,6 +120,9 @@ - (void)_updateBackgroundTask
>                     [self _notifyAssertionsOfImminentSuspension];
>                 });
>             }
>+
>+            // Remember that the assertion has expired in the background so we do not try to re-take it until the application becomes foreground again.
>+            _assertionHasExpiredInTheBackground = YES;
>             [self _releaseBackgroundTask];
>         }];
>     } else if (_assertionsNeedingBackgroundTask.isEmpty())

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Attachments on bug 197385: 368490