UIKitBackgroundCompletionTask - iPhone应用程序崩溃

Question

我正面临一个问题,没有任何解决方案(还).在用户按下Home按钮后,我正在使用后台任务处理程序来启动一些数据获取.代码类似于:

-(void)startRequest {
    UIApplication *app = [UIApplication sharedApplication];
    bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ 
        dispatch_async(dispatch_get_main_queue(), ^{
                [app endBackgroundTask:bgTask];
                bgTask = UIBackgroundTaskInvalid;
            });
    }];
    //..
    //Fetch data with NSURLRequest / delegate method
    //..
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    if ([delegate respondsToSelector:delegateErrorMethod])
        [delegate performSelector:delegateErrorMethod];

    UIApplication *app = [UIApplication sharedApplication];
    if (bgTask != UIBackgroundTaskInvalid) {
       dispatch_async(dispatch_get_main_queue(), ^{
            [app endBackgroundTask:bgTask];
            bgTask = UIBackgroundTaskInvalid;
        });
    }
}


- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    if([delegate respondsToSelector:delegateMethod])
        [delegate performSelector:delegateMethod withObject:self];  

    UIApplication *app = [UIApplication sharedApplication];
    if (bgTask != UIBackgroundTaskInvalid) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [app endBackgroundTask:bgTask];
            bgTask = UIBackgroundTaskInvalid;
        });
    }
}

它运行良好,但有时(没有任何问题或原因,所以它真的不可预测)应用程序崩溃与以下崩溃日志:

Application Specific Information:
MyBackgroundTest[7745] has active assertions beyond permitted time: 
{(
    <SBProcessAssertion: 0x90e65e0> identifier: UIKitBackgroundCompletionTask process: MyBackgroundTest[7745] permittedBackgroundDuration: 600.000000 reason: finishTask owner pid:7745 preventSuspend  preventIdleSleep 
)}

Elapsed total CPU time (seconds): 0.010 (user 0.010, system 0.000), 100% CPU 
Elapsed application CPU time (seconds): 0.000, 0% CPU

Thread 0:
0   libSystem.B.dylib               0x33b5d268 mach_msg_trap + 20
1   libSystem.B.dylib               0x33b5f354 mach_msg + 44
2   CoreFoundation                  0x33a48648 __CFRunLoopServiceMachPort + 88
3   CoreFoundation                  0x33a47ed2 __CFRunLoopRun + 350
4   CoreFoundation                  0x33a47c80 CFRunLoopRunSpecific + 224
5   CoreFoundation                  0x33a47b88 CFRunLoopRunInMode + 52
6   GraphicsServices                0x33b0e4a4 GSEventRunModal + 108
7   GraphicsServices                0x33b0e550 GSEventRun + 56
8   UIKit                           0x32099322 -[UIApplication _run] + 406
9   UIKit                           0x32096e8c UIApplicationMain + 664
10  MyBackgroundTest                0x00002d64 0x1000 + 7524
11  MyBackgroundTest                0x00002d18 0x1000 + 7448

Thread 1:
0   libSystem.B.dylib               0x33b89974 kevent + 24
1   libSystem.B.dylib               0x33c33704 _dispatch_mgr_invoke + 88
2   libSystem.B.dylib               0x33c33174 _dispatch_queue_invoke + 96
3   libSystem.B.dylib               0x33c32b98 _dispatch_worker_thread2 + 120
4   libSystem.B.dylib               0x33bd724a _pthread_wqthread + 258
5   libSystem.B.dylib               0x33bcf970 start_wqthread + 0

Thread 2:
0   libSystem.B.dylib               0x33b5d268 mach_msg_trap + 20
1   libSystem.B.dylib               0x33b5f354 mach_msg + 44
2   CoreFoundation                  0x33a48648 __CFRunLoopServiceMachPort + 88
3   CoreFoundation                  0x33a47ed2 __CFRunLoopRun + 350
4   CoreFoundation                  0x33a47c80 CFRunLoopRunSpecific + 224
5   CoreFoundation                  0x33a47b88 CFRunLoopRunInMode + 52
6   WebCore                         0x304df124 RunWebThread(void*) + 332
7   libSystem.B.dylib               0x33bd6886 _pthread_start + 242
8   libSystem.B.dylib               0x33bcba88 thread_start + 0

Thread 3:
0   libSystem.B.dylib               0x33b5d268 mach_msg_trap + 20
1   libSystem.B.dylib               0x33b5f354 mach_msg + 44
2   CoreFoundation                  0x33a48648 __CFRunLoopServiceMachPort + 88
3   CoreFoundation                  0x33a47ed2 __CFRunLoopRun + 350
4   CoreFoundation                  0x33a47c80 CFRunLoopRunSpecific + 224
5   CoreFoundation                  0x33a47b88 CFRunLoopRunInMode + 52
6   Foundation                      0x336465f6 +[NSURLConnection(NSURLConnectionReallyInternal) _resourceLoadLoop:] + 206
7   Foundation                      0x33624192 -[NSThread main] + 38
8   Foundation                      0x3361d242 __NSThread__main__ + 966
9   libSystem.B.dylib               0x33bd6886 _pthread_start + 242
10  libSystem.B.dylib               0x33bcba88 thread_start + 0

Thread 4:
0   libSystem.B.dylib               0x33b8168c select$DARWIN_EXTSN + 20
1   CoreFoundation                  0x33a7f662 __CFSocketManager + 582
2   libSystem.B.dylib               0x33bd6886 _pthread_start + 242
3   libSystem.B.dylib               0x33bcba88 thread_start + 0

Thread 5:
0   libSystem.B.dylib               0x33bd79e0 __workq_kernreturn + 8
1   libSystem.B.dylib               0x33bd7364 _pthread_wqthread + 540
2   libSystem.B.dylib               0x33bcf970 start_wqthread + 0

Thread 6:
0   libSystem.B.dylib               0x33bd79e0 __workq_kernreturn + 8
1   libSystem.B.dylib               0x33bd7364 _pthread_wqthread + 540
2   libSystem.B.dylib               0x33bcf970 start_wqthread + 0

Unknown thread crashed with unknown flavor: 5, state_count: 1

更新:似乎在这里打开了与此问题相关的更接近的线程.该错误与重定向http连接有关,包括异步和同步NRURL操作.也许,既然NSURLConnection继承自基础框架,那么iPhone上也存在这个bug？

openradar at:1062401

Answer 1

我的调查显示,无论出于什么原因,您都会得到以下例外情况:

TMS[13544] has active assertions beyond permitted time: 
{(
    <SBProcessAssertion: 0x8cb6040> identifier: UIKitBackgroundCompletionTask process: TMS[13544] permittedBackgroundDuration: 600.000000 reason: finishTask owner pid:13544 preventSuspend  preventIdleSleep 
)}

如果代码没有执行`endBackgroundTask:'方法.

这意味着使用beginBackgroundTaskWithExpirationHandler:' call MUST be ended withendBackgroundTask 创建的每个后台任务:'.仔细检查使用正确的任务ID调用`endBackgroundTask:'.