iOS NSURLConnection _resourceLoadLoop crash - ios

Question

I met a strange problem
I am using a NSURLConnection to do some URL request
it work fine on simulator
but it crash on ipad2 5.0
I've tried on iPad1 5.01 ,ipad2 4.33,ipad2 5.01, it worked fine
just crash on ipad2 5.0
I'm not sure what problem is
it seems something wrong with
[NSURLConnection(Loader) _resourceLoadLoop:]
I thought maybe NSURLConnection's delegate may be destroy before NSURLConnection do it's job
so I make retain with the delegate,but still crash
does anybody know what may cause this problem?
crash log:
Date/Time: 2012-02-14 23:31:47.416 +0800
OS Version: iPhone OS 5.0 (9A334)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x000049de
Highlighted Thread: 3
Thread 0 name: Dispatch queue: com.apple.libdispatch-manager
Thread 0:
0 libsystem_kernel.dylib 0x31e973b4 kevent + 24
1 libdispatch.dylib 0x316a6f74 _dispatch_mgr_invoke + 708
2 libdispatch.dylib 0x316a6c92 _dispatch_mgr_thread + 30
Thread 1:
0 libsystem_kernel.dylib 0x31ea7cd4 __workq_kernreturn + 8
1 libsystem_c.dylib 0x30d2730a _pthread_wqthread + 610
2 libsystem_c.dylib 0x30d2709c start_wqthread + 0
Thread 2 name: WebThread
Thread 2:
0 libsystem_kernel.dylib 0x31e97010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x31e97206 mach_msg + 50
2 CoreFoundation 0x371c441c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x371c3154 __CFRunLoopRun + 876
4 CoreFoundation 0x371464d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x3714639e CFRunLoopRunInMode + 98
6 WebCore 0x347ac128 _ZL12RunWebThreadPv + 396
7 libsystem_c.dylib 0x30d2cc16 _pthread_start + 314
8 libsystem_c.dylib 0x30d2cad0 thread_start + 0
Thread 3 name: com.apple.NSURLConnectionLoader
Thread 3:
0 libsystem_kernel.dylib 0x31e97010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x31e97206 mach_msg + 50
2 CoreFoundation 0x371c441c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x371c3154 __CFRunLoopRun + 876
4 CoreFoundation 0x371464d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x3714639e CFRunLoopRunInMode + 98
6 Foundation 0x31ab0bc2 +[NSURLConnection(Loader) _resourceLoadLoop:] + 302
7 Foundation 0x31ab0a8a -[NSThread main] + 66
8 Foundation 0x31b4459a __NSThread__main__ + 1042
9 libsystem_c.dylib 0x30d2cc16 _pthread_start + 314
10 libsystem_c.dylib 0x30d2cad0 thread_start + 0
Thread 4 name: WebCore: CFNetwork Loader
Thread 4:
0 libsystem_kernel.dylib 0x31e97010 mach_msg_trap + 20
1 libsystem_kernel.dylib 0x31e97206 mach_msg + 50
2 CoreFoundation 0x371c441c __CFRunLoopServiceMachPort + 120
3 CoreFoundation 0x371c3154 __CFRunLoopRun + 876
4 CoreFoundation 0x371464d6 CFRunLoopRunSpecific + 294
5 CoreFoundation 0x3714639e CFRunLoopRunInMode + 98
6 WebCore 0x347d569e _ZN7WebCoreL15runLoaderThreadEPv + 122
7 libsystem_c.dylib 0x30d2cc16 _pthread_start + 314
8 libsystem_c.dylib 0x30d2cad0 thread_start + 0
Thread 5 name: com.apple.CFSocket.private
Thread 5:
0 libsystem_kernel.dylib 0x31ea7570 __select + 20
1 CoreFoundation 0x371c866a __CFSocketManager + 726
2 libsystem_c.dylib 0x30d2cc16 _pthread_start + 314
3 libsystem_c.dylib 0x30d2cad0 thread_start + 0
Thread 6 name: WebCore: LocalStorage
Thread 6:
0 libsystem_kernel.dylib 0x31ea7068 __psynch_cvwait + 24
1 libsystem_c.dylib 0x30d2cf2e _pthread_cond_wait + 634
2 libsystem_c.dylib 0x30d2ccaa pthread_cond_wait + 34
3 JavaScriptCore 0x3382040e WTF::ThreadCondition::timedWait(WTF::Mutex&, double) + 54
4 WebCore 0x3490b494 WTF::PassOwnPtr<WebCore::LocalStorageTask> WTF::MessageQueue<WebCore::LocalStorageTask>::waitForMessageFilteredWithTimeout<bool ()(WebCore::LocalStorageTask*)>(WTF::MessageQueueWaitResult&, bool (&)(WebCore::LocalStorageTask*), double) + 52
5 WebCore 0x3490b44a WebCore::LocalStorageThread::threadEntryPointCallback(void*) + 106
6 libsystem_c.dylib 0x30d2cc16 _pthread_start + 314
7 libsystem_c.dylib 0x30d2cad0 thread_start + 0
Unknown thread crashed with ARM Thread State:
r0: 0x0000499a r1: 0x00000000 r2: 0x35fca80d r3: 0x00000000
r4: 0x0014bf50 r5: 0x3e4ce540 r6: 0x00115030 r7: 0x00000000
r8: 0x001d5a60 r9: 0x000000fb r10: 0x2fe5a688 r11: 0x305b1913
ip: 0x00067a2d sp: 0x2fe5a688 lr: 0x00067a49 pc: 0x30878f4e
cpsr: 0x60000030

Answer 1

When the crash logs say "Highlighted Thread:" it may still be a different thread. It is not sure.
All threads except thread 0 (main thread) seem to be stopped at waits or traps. Since thread zero is the only one that appears active, it is the real source of the crash.
Since thread 0 does have main() or UIApplication at the bottom, the stack is probably corrupted or it is in some system functions which use a non-standard way of building stack frames.