App Crash on setRightButton. No idea why - ios

Question

I trying to figure out why my App crashes sometimes on costumers devices. My App is from the AppStore. It happend not always, only in rare cases it seams.
Here is the used codeblock
[UIView animateWithDuration:0.3 animations:^(void){ [self.spinner setAlpha:0.0]; } completion:^(BOOL finished){
if(self.spinner != nil){
[self.spinner removeFromSuperview];
self.spinner = nil;
UIBarButtonItem *externButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemAction target:self action:#selector(openBrowser)];
[self.navigationItem setRightBarButtonItem:externButton animated:YES];
}
}];
It crashes on setRightBarButtomItem:animated:. The codeblock is executed in an Background-Thread. Is that the Problem?
Here the crashlog:
Hardware Model: iPhone5,2
Process: [THE APP] [3052]
Path: (null)
Identifier: [THE APP]
Version: 3.9.0 (3.9.0)
Code Type: ARM
Parent Process: launchd [1]
Date/Time: 2013-11-09 16:07:04.000 +0100
OS Version: iPhone OS 7.0 (11A465)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x7000000c
Crashed Thread: 13
Thread 0:
0 CoreFoundation 0x30781224 __CFStringCreateImmutableFunnel3 + 1160
1 CoreFoundation 0x306dbf38 CFStringCreateWithBytes + 48
2 Foundation 0x310c49e8 -[NSPlaceholderString initWithBytes:length:encoding:] + 100
3 Foundation 0x310c4968 +[NSString stringWithUTF8String:] + 124
4 Foundation 0x310c48b0 NSStringFromClass + 128
5 UIKit 0x32fddb68 +[_UIAppearanceCustomizableClassInfo _customizableClassInfoForViewClass:withGuideClass:] + 260
6 UIKit 0x32fddd90 -[_UIAppearanceCustomizableClassInfo _superClassInfo] + 160
7 UIKit 0x32fddcc8 existingAppearancesNodesInNodeForClassAndSuperclasses + 136
8 UIKit 0x32fdd1d0 +[_UIAppearance _applyInvocationsTo:window:matchingSelector:] + 164
9 UIKit 0x32fdd120 +[_UIAppearance _applyInvocationsTo:window:] + 24
10 UIKit 0x32f32488 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 176
11 QuartzCore 0x32bb9f40 -[CALayer layoutSublayers] + 140
12 QuartzCore 0x32bb5760 CA::Layer::layout_if_needed(CA::Transaction*) + 344
13 UIKit 0x32f47410 -[UIView(Hierarchy) layoutBelowIfNeeded] + 532
14 UIKit 0x32fe9810 -[UIBarButtonItem(UIStatic) _leftRightImagePaddingForEdgeMarginInNavBarIsMini:] + 360
15 UIKit 0x32fcf140 -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:forItemAtIndex:returnedIdealWidthOfTextContent:availableLayoutWidthForTextContent:idealBackButtonWidth:] + 2504
16 UIKit 0x32fc6e38 -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:forItemAtIndex:] + 632
17 UIKit 0x32fc6bb8 -[UINavigationBar _getTitleViewFrame:leftViewFrames:rightViewFrames:] + 136
18 UIKit 0x32fcd080 -[UINavigationBar _setLeftViews:rightViews:] + 1248
19 UIKit 0x32fca2b8 -[UINavigationBar _pushNavigationItem:transition:] + 464
20 UIKit 0x32fc9e98 __71-[UINavigationController pushViewController:transition:forceImmediate:]_block_invoke + 148
21 UIKit 0x32fe13a0 -[UINavigationController _startDeferredTransitionIfNeeded:] + 868
22 UIKit 0x32fe0fe8 -[UINavigationController __viewWillLayoutSubviews] + 44
23 UIKit 0x32fe0f78 -[UILayoutContainerView layoutSubviews] + 180
24 UIKit 0x32f32530 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 344
25 QuartzCore 0x32bb9f40 -[CALayer layoutSublayers] + 140
26 QuartzCore 0x32bb5760 CA::Layer::layout_if_needed(CA::Transaction*) + 344
27 QuartzCore 0x32bb55f8 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 16
28 QuartzCore 0x32bb5008 CA::Context::commit_transaction(CA::Transaction*) + 224
29 QuartzCore 0x32bb4e18 CA::Transaction::commit() + 308
30 QuartzCore 0x32baeb48 CA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 52
31 CoreFoundation 0x30777f70 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 20
32 CoreFoundation 0x307758f8 __CFRunLoopDoObservers + 280
33 CoreFoundation 0x30775c48 __CFRunLoopRun + 736
34 CoreFoundation 0x306e0540 CFRunLoopRunSpecific + 524
35 CoreFoundation 0x306e0320 CFRunLoopRunInMode + 104
36 GraphicsServices 0x354172e8 GSEventRunModal + 136
37 UIKit 0x32f971e0 UIApplicationMain + 1132
38 [THE APP] 0x00059f48 main (main.m:21)
Thread 1:
0 libsystem_kernel.dylib 0x3b043838 kevent64 + 24
1 libdispatch.dylib 0x3af8c640 _dispatch_mgr_thread + 36
Thread 2:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 3:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 4:
0 libsystem_kernel.dylib 0x3b043a84 mach_msg_trap + 20
1 CoreFoundation 0x30777560 __CFRunLoopServiceMachPort + 156
2 CoreFoundation 0x30775c80 __CFRunLoopRun + 792
3 CoreFoundation 0x306e0540 CFRunLoopRunSpecific + 524
4 CoreFoundation 0x306e0320 CFRunLoopRunInMode + 104
5 Foundation 0x3111b650 +[NSURLConnection(Loader) _resourceLoadLoop:] + 320
6 Foundation 0x31190dc0 __NSThread__main__ + 1056
7 libsystem_pthread.dylib 0x3b0bcc58 _pthread_body + 136
8 libsystem_pthread.dylib 0x3b0bcbc8 _pthread_start + 96
Thread 5:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 6:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 7:
0 libsystem_kernel.dylib 0x3b056550 __semwait_signal + 24
1 Foundation 0x311904d8 +[NSThread sleepForTimeInterval:] + 144
2 [THE APP] 0x0014a870 -[KSCrashDeadlockMonitor runMonitor] + 232
3 Foundation 0x31190dc0 __NSThread__main__ + 1056
4 libsystem_pthread.dylib 0x3b0bcc58 _pthread_body + 136
5 libsystem_pthread.dylib 0x3b0bcbc8 _pthread_start + 96
Thread 8:
0 libsystem_kernel.dylib 0x3b043a84 mach_msg_trap + 20
1 [THE APP] 0x001469e0 ksmachexc_i_handleExceptions + 128
2 libsystem_pthread.dylib 0x3b0bcc58 _pthread_body + 136
3 libsystem_pthread.dylib 0x3b0bcbc8 _pthread_start + 96
Thread 9:
Thread 10:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 11:
0 libsystem_kernel.dylib 0x3b056440 select$DARWIN_EXTSN + 20
1 libsystem_pthread.dylib 0x3b0bcc58 _pthread_body + 136
2 libsystem_pthread.dylib 0x3b0bcbc8 _pthread_start + 96
Thread 12:
0 libsystem_kernel.dylib 0x3b056c7c __workq_kernreturn + 8
Thread 13 Crashed:
0 libobjc.A.dylib 0x3aaa1b66 objc_msgSend + 6
1 UIKit 0x32fe4b80 -[UINavigationItem updateNavigationBarButtonsAnimated:] + 156
2 UIKit 0x32fe46e8 -[UINavigationItem setRightBarButtonItem:animated:] + 156
3 [THE APP] 0x000c6058 -[ProductViewController loadXML] (ProductViewController.m:978)
4 Foundation 0x31190dc0 __NSThread__main__ + 1056
5 libsystem_pthread.dylib 0x3b0bcc58 _pthread_body + 136
6 libsystem_pthread.dylib 0x3b0bcbc8 _pthread_start + 96
Thread 13 crashed with ARM Thread State:
r0: 0x15e78c40 r1: 0x33517435 r2: 0x00000000 r3: 0x00000000
r4: 0x33517435 r5: 0x33530ea0 r6: 0x15e83b00 r7: 0x037a2be0
r8: 0x15d56570 r9: 0x70000000 r10: 0x00000000 r11: 0x00000001
ip: 0x3b5be224 sp: 0x037a27f0 lr: 0x32fccffb pc: 0x3aaa1b66
cpsr: 0x20000030
Binary Images:
[cut cause of char limit]
Any ideas? Thanks for the help!

Answer 1

First of all you shouldn't run this in a background thread.
Secondly BAD_ACCESS usually happens when you over-release something.
I can't figure out where you over-release but maybe you can find it in your code. my guess is the navigation item tries to release something before setting your externButton...
EDIT: where is this code happening at? could be that the UIViewController isn't pushed anymore into the navigation controller or not the top one by the time this code is executed?

Answer 2

Things that update the UI should be on the main thread.
dispatch_async(dispatch_get_main_queue(), ^{ /* UI code goes here */ });