[webkit-dev] WebCore crashes calling layout code on wrong thread (iOS 9 SDK only)

[Ian Ragsdale]

Hi all, I'm running into a strange crash when I build my application using the iOS 9 SDK (we don't see this crash in prior versions of our app).

The error we see is "NSInternalInconsistencyException accessing _cachedSystemAnimationFence requires the main thread", and the stack trace is below.

Any ideas on how I might track this down or avoid it?

Thanks,
Ian

Thread : Fatal Exception: NSInternalInconsistencyException
0  CoreFoundation                 6527766344 __exceptionPreprocess + 124
1  libobjc.A.dylib                6878281600 objc_exception_throw + 56
2  CoreFoundation                 6527766040 +[NSException raise:format:]
3  Foundation                     6543444508 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 112
4  UIKit                          6620261688 -[UIApplication _cachedSystemAnimationFenceCreatingIfNecessary:] + 200
5  UIKit                          6620261884 -[UIApplication _systemAnimationFenceCreatingIfNecessary:] + 24
6  UIKit                          6620609076 +[UIWindow _synchronizedDrawingFence] + 116
7  UIKit                          6625701528 -[_UIRemoteViewController synchronizeAnimationsInActions:] + 124
8  UIKit                          6625679332 -[_UISizeTrackingView _geometryChanges:forAncestor:] + 540
9  UIKit                          6620678428 -[UIView _notifyGeometryObserversWithChangeInfo:] + 272
10 UIKit                          6617880096 -[UIView setCenter:] + 408
11 UIKit                          6618589764 -[UIView(Geometry) _applyISEngineLayoutValues] + 600
12 UIKit                          6617592576 -[UIView(Geometry) _resizeWithOldSuperviewSize:] + 136
13 CoreFoundation                 6526679440 __53-[__NSArrayM enumerateObjectsWithOptions:usingBlock:]_block_invoke + 132
14 CoreFoundation                 6526679176 -[__NSArrayM enumerateObjectsWithOptions:usingBlock:] + 308
15 UIKit                          6617521936 -[UIView(Geometry) resizeSubviewsWithOldSize:] + 116
16 UIKit                          6618590092 -[UIView(AdditionalLayoutSupport) _is_layout] + 128
17 UIKit                          6620696916 -[UIView(Hierarchy) _updateConstraintsAsNecessaryAndApplyLayoutFromEngine] + 756
18 UIKit                          6617479084 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 644
19 QuartzCore                     6609087320 -[CALayer layoutSublayers] + 148
20 QuartzCore                     6609065828 CA::Layer::layout_if_needed(CA::Transaction*) + 292
21 QuartzCore                     6609065508 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 32
22 QuartzCore                     6609063104 CA::Context::commit_transaction(CA::Transaction*) + 252
23 QuartzCore                     6609062408 CA::Transaction::commit() + 512
24 QuartzCore                     6609035512 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 80
25 CoreFoundation                 6527466448 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 32
26 CoreFoundation                 6527457652 __CFRunLoopDoObservers + 372
27 CoreFoundation                 6526602432 CFRunLoopRunSpecific + 416
28 WebCore                        6827173196 RunWebThread(void*) + 456
29 libsystem_pthread.dylib        6888979240 _pthread_body + 156
30 libsystem_pthread.dylib        6888979084 _pthread_body
31 libsystem_pthread.dylib        6888968232 thread_start + 4