Why did this app crash while in the background? - iphone

Question

My app uses background location for GPS updates. I've registered it for background location updates, and while it's running in background, it always crashes like this.
Since I haven't written most of this code, I really have no idea what happened.
I have checked the memory allocations and there doesn't seem to be much of a problem there. Here's a crash report:
Incident Identifier: 39F6F622-1274-4B6C-BA19-32D10E04E309
CrashReporter Key: 4757f4c5e5f009daf18eb0c512f729356c3e5de4
Hardware Model: iPhone3,1
Process: Get Off Now! [3040]
Path: /var/mobile/Applications/43D41F77-B225-4F47-AFB0-D2F2E00E18DF/Get Off Now!.app/Get Off Now!
Identifier: Get Off Now!
Version: ??? (???)
Code Type: ARM (Native)
Parent Process: launchd [1]
Date/Time: 2010-12-22 13:31:29.293 +0800
OS Version: iPhone OS 4.1 (8B117)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGBUS)
Exception Codes: KERN_PROTECTION_FAILURE at 0x0000000d
Crashed Thread: 0
Thread 0 Crashed:
0 libobjc.A.dylib 0x000027d8 objc_msgSend + 16
1 CoreFoundation 0x000042ae CFRetain + 62
2 CoreFoundation 0x0005ab58 CFMessagePortInvalidate + 304
3 CoreFoundation 0x0005b05e CFMessagePortIsValid + 42
4 CoreLocation 0x000030f8 CLClientIsValid + 12
5 CoreLocation 0x00004b10 CLClientSendAndCache(__CLClient*, CLDaemonCommType, void*, int, unsigned char, unsigned char) + 40
6 CoreLocation 0x000051cc CLClientHandleWatchdogTimerExpiry(__CFRunLoopTimer*, void*) + 24
7 CoreFoundation 0x000567f4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 8
8 CoreFoundation 0x000562a6 __CFRunLoopDoTimer + 854
9 CoreFoundation 0x0002779e __CFRunLoopRun + 1082
10 CoreFoundation 0x00027270 CFRunLoopRunSpecific + 224
11 CoreFoundation 0x00027178 CFRunLoopRunInMode + 52
12 GraphicsServices 0x000045ec GSEventRunModal + 108
13 GraphicsServices 0x00004698 GSEventRun + 56
14 UIKit 0x0000411c -[UIApplication _run] + 396
15 UIKit 0x00002128 UIApplicationMain + 664
16 Get Off Now! 0x00002406 0x1000 + 5126
17 Get Off Now! 0x000023d0 0x1000 + 5072
Thread 1:
0 libSystem.B.dylib 0x0002d330 kevent + 24
1 libSystem.B.dylib 0x000d6b6c _dispatch_mgr_invoke + 88
2 libSystem.B.dylib 0x000d65bc _dispatch_queue_invoke + 96
3 libSystem.B.dylib 0x000d675c _dispatch_worker_thread2 + 120
4 libSystem.B.dylib 0x0007a67a _pthread_wqthread + 258
5 libSystem.B.dylib 0x00073190 start_wqthread + 0
Thread 2:
0 libSystem.B.dylib 0x00000cf4 semaphore_wait_signal_trap + 8
1 libSystem.B.dylib 0x0002e4ee semaphore_wait_signal + 2
2 libSystem.B.dylib 0x00002ae4 pthread_mutex_lock + 248
3 WebCore 0x00002620 _WebTryThreadLock(bool) + 140
4 WebCore 0x00002566 WebRunLoopLock(__CFRunLoopObserver*, unsigned long, void*) + 18
5 CoreFoundation 0x00030236 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 10
6 CoreFoundation 0x000300aa __CFRunLoopDoObservers + 406
7 CoreFoundation 0x000276c0 __CFRunLoopRun + 860
8 CoreFoundation 0x00027270 CFRunLoopRunSpecific + 224
9 CoreFoundation 0x00027178 CFRunLoopRunInMode + 52
10 WebCore 0x000024e2 RunWebThread(void*) + 362
11 libSystem.B.dylib 0x0007a27e _pthread_start + 242
12 libSystem.B.dylib 0x0006f2a8 thread_start + 0
Thread 3:
0 libSystem.B.dylib 0x0007b19c __workq_kernreturn + 8
1 libSystem.B.dylib 0x0007a790 _pthread_wqthread + 536
2 libSystem.B.dylib 0x00073190 start_wqthread + 0
Thread 4:
0 libSystem.B.dylib 0x0007b19c __workq_kernreturn + 8
1 libSystem.B.dylib 0x0007a790 _pthread_wqthread + 536
2 libSystem.B.dylib 0x00073190 start_wqthread + 0
Thread 0 crashed with ARM Thread State:
r0: 0x001a01c0 r1: 0x33024270 r2: 0x00000005 r3: 0x3002d7c9
r4: 0x00000005 r5: 0x3e1af5e4 r6: 0x00000017 r7: 0x2fffeac0
r8: 0x00000004 r9: 0x001fc098 r10: 0x00855864 r11: 0x2fffeb48
ip: 0x3e19c3f0 sp: 0x2fffeaa8 lr: 0x307fc2b5 pc: 0x3002d7d8
cpsr: 0x20000030
This is another way it crashes; it looks the same, except it uses 100% CPU for a long time:
Incident Identifier: 61B42F36-021F-48D2-B180-112527BAE5CF
CrashReporter Key: 4757f4c5e5f009daf18eb0c512f729356c3e5de4
Hardware Model: iPhone3,1
Process: Get Off Now! [3751]
Path: /var/mobile/Applications/43D41F77-B225-4F47-AFB0-D2F2E00E18DF/Get Off Now!.app/Get Off Now!
Identifier: Get Off Now!
Version: ??? (???)
Code Type: ARM (Native)
Parent Process: launchd [1]
Date/Time: 2010-12-23 13:06:50.363 +0800
OS Version: iPhone OS 4.1 (8B117)
Report Version: 104
Exception Type: 00000020
Exception Codes: 0x8badf00d
Highlighted Thread: 0
Application Specific Information:
Get Off Now![3751] has active assertions beyond permitted time:
{(
<SBProcessAssertion: 0xca2a8a0> identifier: CoreLocationRegistration process: Get Off Now![3751] permittedBackgroundDuration: 600.000000 reason: finishTask owner pid:3751 preventSuspend preventIdleSleep
)}
Elapsed total CPU time (seconds): 600.010 (user 19.350, system 580.660), 100% CPU
Elapsed application CPU time (seconds): 575.320, 96% CPU
Thread 0:
0 libSystem.B.dylib 0x00004f0c OSSpinLockLock + 44
1 CoreFoundation 0x0005aa42 CFMessagePortInvalidate + 26
2 CoreFoundation 0x0005b05e CFMessagePortIsValid + 42
3 CoreLocation 0x000030f8 CLClientIsValid + 12
4 CoreLocation 0x00004b10 CLClientSendAndCache(__CLClient*, CLDaemonCommType, void*, int, unsigned char, unsigned char) + 40
5 CoreLocation 0x000051cc CLClientHandleWatchdogTimerExpiry(__CFRunLoopTimer*, void*) + 24
6 CoreFoundation 0x000567f4 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 8
7 CoreFoundation 0x000562a6 __CFRunLoopDoTimer + 854
8 CoreFoundation 0x0002779e __CFRunLoopRun + 1082
9 CoreFoundation 0x00027270 CFRunLoopRunSpecific + 224
10 CoreFoundation 0x00027178 CFRunLoopRunInMode + 52
11 GraphicsServices 0x000045ec GSEventRunModal + 108
12 GraphicsServices 0x00004698 GSEventRun + 56
13 UIKit 0x0000411c -[UIApplication _run] + 396
14 UIKit 0x00002128 UIApplicationMain + 664
15 Get Off Now! 0x000022de main (main.m:13)
16 Get Off Now! 0x000022a8 start + 32
Thread 1:
0 libSystem.B.dylib 0x0002d330 kevent + 24
1 libSystem.B.dylib 0x000d6b6c _dispatch_mgr_invoke + 88
2 libSystem.B.dylib 0x000d65bc _dispatch_queue_invoke + 96
3 libSystem.B.dylib 0x000d675c _dispatch_worker_thread2 + 120
4 libSystem.B.dylib 0x0007a67a _pthread_wqthread + 258
5 libSystem.B.dylib 0x00073190 start_wqthread + 0
Thread 2:
0 libSystem.B.dylib 0x00000c98 mach_msg_trap + 20
1 libSystem.B.dylib 0x00002d64 mach_msg + 44
2 CoreFoundation 0x00027c38 __CFRunLoopServiceMachPort + 88
3 CoreFoundation 0x000274c2 __CFRunLoopRun + 350
4 CoreFoundation 0x00027270 CFRunLoopRunSpecific + 224
5 CoreFoundation 0x00027178 CFRunLoopRunInMode + 52
6 WebCore 0x000024e2 RunWebThread(void*) + 362
7 libSystem.B.dylib 0x0007a27e _pthread_start + 242
8 libSystem.B.dylib 0x0006f2a8 thread_start + 0
Unknown thread crashed with unknown flavor: 5, state_count: 1

Answer 1

I think you need to check some objects which are released by other threads, but they are accessed by main thread. I encountered something like this, and it was because I accessed some objects which had been released.

Answer 2

I had precisely the same crash logs being generated. I have a main thread, which uses an NSOperationQueue to spawn a data download thread, which then uses performSelectorOnMainThread when finished.
In my didupdatelocation method, I was cycling through an array, launching a local notification in some cases. It seemed to fail on the SECOND instance of a local notification (for the same array item), but I cannot be sure. I did try symbolicating the logs, but there is some missing file error with 4.2.1, so I'd copied in symbols from 4.2, and couldn't get atos to work (but that was probably my fault).
Last night I made the following changes, and all seems to be resolved:
1) changed all self.locationManager notation to just locationManager
2) removed everything from the dealloc method in the appdelegate (aside from super)