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

[Ian Ragsdale]

Sorry I haven't gotten this bug in yet, has taken us quite some time to
find steps to reproduce. Turns out it does NOT require using the iOS 9 SDK
to build, just that the device has iOS 9+ installed. We also just now
figured out today that having a custom keyboard activated is key to
reproducing the crash, this never happens with the stock keyboard.

Will try to get a more complete report submitted soon, but wanted to get
this over quickly in case it causes a light bulb to come on.

- Ian

On Oct 26, 2015, at 1:10 PM, Simon Fraser <simon.fraser at apple.com> wrote:

We’re tracking an issue similar to this internally. Could you please file a
bug report at bug reporter.apple.com, with a copy of the app and steps to
reproduce?

Thanks
Simon

On Oct 26, 2015, at 11:05 AM, Ian Ragsdale <ian.ragsdale at gmail.com> wrote:

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
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