UIKitBackgroundCompletionTask - iPhone 应用程序崩溃

Question

UIKitBackgroundCompletionTask - iPhone 应用程序崩溃

4

我遇到了一个问题，目前还没有解决方案。我正在使用后台任务处理程序，在用户按下Home按钮后启动一些数据获取。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;
        });
    }
}

这个应用程序工作得很好，但有时候（没有任何问题或原因，所以真的很不可预测），会出现以下崩溃日志而导致应用程序崩溃：

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： 似乎与此问题相关的更接近的线程在这里开放。该错误与重定向http连接有关，包括异步和同步NRURL操作。也许，由于NSURLConnection继承自基础框架，因此iPhone上也存在该错误？

openradar网址：1062401

- valvoline

对我来说，你的应用程序似乎被看门狗定时器杀死了。有可能是url连接挂起时间太长了吗？ - Axel

setTimeOutProperty是90秒。据我所知，这是NSURLConnection允许的最长时间。 - valvoline

2个回答

1

这种异常是由于后台任务未能及时结束引起的。虽然我不能百分之百确定，但我认为此特定崩溃是因为您传递到 beginBackgroundTaskWithExpirationHandler: 的代码块导致的，如果连接仍未完成且系统想要结束您的后台任务，则会调用该代码块。

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

- (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:(void (^)(void))handler的文档介绍了handler: "您应该使用此处理程序来清理并标记后台任务的结束"。

由于dispatch_async调用，当调用此块时，实际上并没有结束任务。在此块调用返回之后（和您的dispatch_async块运行之后），才会结束任务。我认为，在看门狗关闭您的应用程序之前，大多数时间都有足够的时间运行第二个块，但有时候不是这样。因此，您应该立即结束后台任务，然后为任何其他清理需要进行dispatch_async：

UIApplication *app = [UIApplication sharedApplication];
__block UIBackgroundTaskIdentifier tid = bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ 
    [app endBackgroundTask:tid];
    dispatch_async(dispatch_get_main_queue(), ^{
            bgTask = UIBackgroundTaskInvalid;
        });
}];

此外，文档中指出：“处理程序在主线程上同步调用”，因此您实际上没有必要执行dispatch_async。您只需要执行以下操作：

UIApplication *app = [UIApplication sharedApplication];
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ 
    [app endBackgroundTask:bgTask];
    bgTask = UIBackgroundTaskInvalid;
}];

- jasongregori

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可以查看英文原文，
原文链接

- ten0s · Accepted Answer

我的调查显示，无论原因是什么，你会得到以下异常：

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，那么会出现问题。

这意味着使用beginBackgroundTaskWithExpirationHandler:'创建的每个后台任务都必须使用endBackgroundTask:'结束。请仔细检查是否使用了正确的任务ID调用了`endBackgroundTask:'。