title: Unknown exception and crash
body: <p>My application crashes when I try to scroll the tableview very fast or reload the data from remote. Everything seems to be working fine, when I let the remote fetch happen first and then scroll the tableview. I have no idea what the crash log below means. It just works fine sometimes and crashes sometime. </p>
  
  <pre><code>Incident Identifier: 710A120C-97E3-45C8-A7B2-E6A7BD98BC1A
  CrashReporter Key:   8bd54d8428128b9e6b8c04d59b86c40cccf33457
  Hardware Model:      iPhone5,2
  Process:         MyApp [5294]
  Path:            /var/mobile/Applications/B6ED5B19-B8D7-4146-90A2-F709AE35292F/MyApp.app/MyApp
  Identifier:      MyApp
  Version:         ??? (???)
  Code Type:       ARM (Native)
  Parent Process:  launchd [1]
  
  Date/Time:       2013-02-26 16:45:27.693 +0200
  OS Version:      iOS 6.1.2 (10B146)
  Report Version:  104
  
  Exception Type:  EXC_CRASH (SIGSEGV)
  Exception Codes: 0x0000000000000000, 0x0000000000000000
  Crashed Thread:  1
  
  Thread 0 name:  Dispatch queue: com.apple.main-thread
  Thread 0:
  0   libobjc.A.dylib                 0x3c3f658a _cache_getImp + 10
  1   libobjc.A.dylib                 0x3c3f6fa0 lookUpMethod + 24
  2   libobjc.A.dylib                 0x3c3f81e2 class_respondsToSelector + 26
  3   CoreFoundation                  0x3470a750 objectIsKindOfClass + 32
  4   CoreFoundation                  0x3470a49c __handleUncaughtException + 64
  5   libobjc.A.dylib                 0x3c3fba46 _objc_terminate() + 126
  6   libc++abi.dylib                 0x3be48118 safe_handler_caller(void (*)()) + 76
  7   libc++abi.dylib                 0x3be481b0 std::terminate() + 16
  8   libc++abi.dylib                 0x3be49626 __cxa_rethrow + 90
  9   libobjc.A.dylib                 0x3c3fb9b0 objc_exception_rethrow + 8
  10  CoreFoundation                  0x3465129c CFRunLoopRunSpecific + 452
  11  CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  12  GraphicsServices                0x3822f336 GSEventRunModal + 70
  13  UIKit                           0x3656d2b4 UIApplicationMain + 1116
  14  MyApp                       0x000910a2 0x44000 + 315554
  15  MyApp                       0x0004668c 0x44000 + 9868
  
  Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
  Thread 1 Crashed:
  0   libsystem_kernel.dylib          0x3c8df5d0 kevent64 + 24
  1   libdispatch.dylib               0x3c81ad22 _dispatch_mgr_invoke + 806
  2   libdispatch.dylib               0x3c816374 _dispatch_mgr_thread + 32
  
  Thread 2 name:  WebThread
  Thread 2:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  6   WebCore                         0x3a650390 RunWebThread(void*) + 440
  7   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  8   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 3 name:  com.apple.NSURLConnectionLoader
  Thread 3:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  6   Foundation                      0x34f9e888 +[NSURLConnection(Loader) _resourceLoadLoop:] + 304
  7   Foundation                      0x3502222c __NSThread__main__ + 968
  8   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  9   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 4:
  0   libsystem_kernel.dylib          0x3c8efd98 __workq_kernreturn + 8
  1   libsystem_c.dylib               0x3c83dad6 _pthread_workq_return + 14
  2   libsystem_c.dylib               0x3c83d7f2 _pthread_wqthread + 362
  3   libsystem_c.dylib               0x3c83d680 start_wqthread + 4
  
  Thread 5:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  6   Foundation                      0x34f755be -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 250
  7   Foundation                      0x35018c40 -[NSRunLoop(NSRunLoop) run] + 76
  8   MyApp                       0x0016b900 0x44000 + 1210624
  9   Foundation                      0x3502222c __NSThread__main__ + 968
  10  libsystem_c.dylib               0x3c8480de _pthread_start + 306
  11  libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 6:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  6   Foundation                      0x34f755be -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 250
  7   Foundation                      0x35018c40 -[NSRunLoop(NSRunLoop) run] + 76
  8   MyApp                       0x000e63d0 0x44000 + 664528
  9   Foundation                      0x3502222c __NSThread__main__ + 968
  10  libsystem_c.dylib               0x3c8480de _pthread_start + 306
  11  libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 7 name:  com.apple.CFSocket.private
  Thread 7:
  0   libsystem_kernel.dylib          0x3c8ef594 __select + 20
  1   CoreFoundation                  0x346e3474 __CFSocketManager + 676
  2   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  3   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 8:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346afc46 CFRunLoopRun + 94
  6   MyApp                       0x00115d7e 0x44000 + 859518
  7   Foundation                      0x3502222c __NSThread__main__ + 968
  8   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  9   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 9:
  0   libsystem_kernel.dylib          0x3c8efd98 __workq_kernreturn + 8
  1   libsystem_c.dylib               0x3c83dad6 _pthread_workq_return + 14
  2   libsystem_c.dylib               0x3c83d7f2 _pthread_wqthread + 362
  3   libsystem_c.dylib               0x3c83d680 start_wqthread + 4
  
  Thread 10:
  0   libsystem_kernel.dylib          0x3c8efd98 __workq_kernreturn + 8
  1   libsystem_c.dylib               0x3c83dad6 _pthread_workq_return + 14
  2   libsystem_c.dylib               0x3c83d7f2 _pthread_wqthread + 362
  3   libsystem_c.dylib               0x3c83d680 start_wqthread + 4
  
  Thread 11 name:  JavaScriptCore::BlockFree
  Thread 11:
  0   libsystem_kernel.dylib          0x3c8ef08c __psynch_cvwait + 24
  1   libsystem_c.dylib               0x3c840afc _pthread_cond_wait + 644
  2   libsystem_c.dylib               0x3c840870 pthread_cond_timedwait + 40
  3   JavaScriptCore                  0x38625df6 WTF::ThreadCondition::timedWait(WTF::Mutex&amp;, double) + 102
  4   JavaScriptCore                  0x38738532 JSC::BlockAllocator::blockFreeingThreadMain() + 78
  5   JavaScriptCore                  0x3874b030 WTF::wtfThreadEntryPoint(void*) + 12
  6   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  7   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 12 name:  JavaScriptCore::Marking
  Thread 12:
  0   libsystem_kernel.dylib          0x3c8ef08c __psynch_cvwait + 24
  1   libsystem_c.dylib               0x3c840afc _pthread_cond_wait + 644
  2   libsystem_c.dylib               0x3c84acf8 pthread_cond_wait + 36
  3   JavaScriptCore                  0x386cb6dc JSC::SlotVisitor::drainFromShared(JSC::SlotVisitor::SharedDrainMode) + 140
  4   JavaScriptCore                  0x386cb620 JSC::MarkStackThreadSharedData::markingThreadMain() + 140
  5   JavaScriptCore                  0x3874b030 WTF::wtfThreadEntryPoint(void*) + 12
  6   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  7   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 13 name:  WebCore: CFNetwork Loader
  Thread 13:
  0   libsystem_kernel.dylib          0x3c8dee30 mach_msg_trap + 20
  1   libsystem_kernel.dylib          0x3c8defd0 mach_msg + 48
  2   CoreFoundation                  0x346df2b6 __CFRunLoopServiceMachPort + 126
  3   CoreFoundation                  0x346de02c __CFRunLoopRun + 900
  4   CoreFoundation                  0x34651238 CFRunLoopRunSpecific + 352
  5   CoreFoundation                  0x346510c4 CFRunLoopRunInMode + 100
  6   WebCore                         0x3a6eaccc WebCore::runLoaderThread(void*) + 140
  7   JavaScriptCore                  0x3874b030 WTF::wtfThreadEntryPoint(void*) + 12
  8   libsystem_c.dylib               0x3c8480de _pthread_start + 306
  9   libsystem_c.dylib               0x3c847fa4 thread_start + 4
  
  Thread 14:
  0   libsystem_kernel.dylib          0x3c8efd98 __workq_kernreturn + 8
  1   libsystem_c.dylib               0x3c83dad6 _pthread_workq_return + 14
  2   libsystem_c.dylib               0x3c83d7f2 _pthread_wqthread + 362
  3   libsystem_c.dylib               0x3c83d680 start_wqthread + 4
  
  Thread 1 crashed with ARM Thread State (32-bit):
      r0: 0x00000004    r1: 0x00000000      r2: 0x00000000      r3: 0x0042c714
      r4: 0x00000001    r5: 0x00000000      r6: 0x0042c744      r7: 0x0042c764
      r8: 0x00000000    r9: 0x0042c6c8     r10: 0x3e3a2188     r11: 0x00000002
      ip: 0x00000171    sp: 0x0042c6d0      lr: 0x3c81ad27      pc: 0x3c8df5d0
    cpsr: 0x60000010
  </code></pre>
  
  <p>I would be really happy if anybody could explain me what this crash log could relate to and how I could solve it. Many many thanks to all those who are willing to help others.</p>