title: iOS WebTryThreadLock crash
body: <p>I have a crash in my app that I cannot debug for the life of me. When plugged in and debugging from Xcode on a device and NSZombieEnabled on, I do not receive the crash. When I unplug and run the app on its own, or turn of NSZombieEnabled, it crashes every time. </p>
  
  <p>Here is what I get when I turn off NSZombieEnabled: EXC_BAD_ACCESS</p>
  
  <pre><code>bool _WebTryThreadLock(bool), 0x58a260: Multiple locks on web thread not allowed! Please file a bug. Crashing now...
  1   _ZL17_WebTryThreadLockb
  2   _ZL14WebRunLoopLockP19__CFRunLoopObservermPv
  3   __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__
  4   __CFRunLoopDoObservers
  5   __CFRunLoopRun
  6   CFRunLoopRunSpecific
  7   CFRunLoopRunInMode
  8   _ZL12RunWebThreadPv
  9   _pthread_start
  10  thread_start
  </code></pre>
  
  <p>Here is the stack trace from the test flight:</p>
  
  <pre><code>0 App 0x001ff492 testflight_backtrace + 142
  1 App 0x001fffac TFSignalHandler + 212
  2 libsystem_c.dylib 0x349e9538 _sigtramp + 48
  3 JavaScriptCore 0x34b66aee WTFReportBacktrace + 146
  4 WebCore 0x33ed5676 _ZL14WebRunLoopLockP19__CFRunLoopObservermPv + 30
  5 CoreFoundation 0x33b39b4a __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 18
  6 CoreFoundation 0x33b37d86 __CFRunLoopDoObservers + 258
  7 CoreFoundation 0x33b3804e __CFRunLoopRun + 614
  8 CoreFoundation 0x33abb4dc CFRunLoopRunSpecific + 300
  9 CoreFoundation 0x33abb3a4 CFRunLoopRunInMode + 104
  10 WebCore 0x33f7712e _ZL12RunWebThreadPv + 402
  11 libsystem_c.dylib 0x349a0c1c _pthread_start + 320
  12 libsystem_c.dylib 0x349a0ad7 thread_start + 7
  </code></pre>
  
  <p>I have had this crash before, and I have resolved it by throwing in the line to my viewDidLoad method on one of the view controllers where the crashing was occurring:</p>
  
  <pre><code>[[NSRunLoop currentRunLoop] runUntilDate: [NSDate dateWithTimeIntervalSinceNow:0.01]];
  </code></pre>
  
  <p>This line is not helping now.</p>
  
  <p>The process that causes the app to crash is: 
  Present share view controller, 
  Dismiss share view controller, 
  Switch tab view on tabViewController, 
   Press button which presents share2 view controller</p>
  
  <p>I am not doing any background processing or changing any UI, the crash happens RIGHT when you hit the button that presents the share2 view controller. This crash was not happening a few days ago and I have tried to revert all of my changes to find the cause of the issue, but I had no luck.</p>
  
  <p>I have also scoured the internet for this error, and none of the info I found has helped me.</p>
  
  <p>Any advice to point me in the right direction would be greatly appreciated, thanks!</p>