iOS11 看门狗超时崩溃 (0x8badf00d) 但代码不在堆栈中
iOS11 watchdog timeout crashes (0x8badf00d) but code not on stack
我正在调试用户报告我们的应用程序从 iOS11 开始在后台反复退出，即使在活跃使用期间（例如，用户在几秒钟内将我们和 returns 置于后台或一分钟，才发现它重新启动了）。崩溃日志都揭示了相同的原因：看门狗超时。以下是此类崩溃日志中的相关内容：
Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: Namespace <0xF>, Code 0x8badf00d
Triggered by Thread: 0
我意识到我们的代码在接收推送通知或后台运行时的运行时间有限。我们确实使用 UIBackgroundTasks（使用 Alamofire Networking，FWIW），并且我们确实有执行此操作的过期处理程序：
backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask:backgroundTask];
backgroundTask = UIBackgroundTaskInvalid; // Set the task to be invalid
DebugLog(@"Ended because expiration");
}];
关于这些崩溃报告最令人费解的是我们的代码不在堆栈中。从 this Apple discussion of the 0x8badf00d exception code 可以看出，违规代码实际上是在主线程上主动执行的。
但是，在我的例子中，none 的堆栈曾经执行过我的任何代码。这是一个有代表性的样本：
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 GraphicsServices 0x000000018546cf84 0x185462000 + 44932
6 UIKit 0x000000018d37a0bc 0x18d307000 + 471228
7 MyApp 0x0000000102a6572c main + 87852 (main.m:22)
8 libdyld.dylib 0x00000001830fa56c 0x1830f9000 + 5484
Thread 1 name: com.apple.uikit.eventfetch-thread
Thread 1:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 Foundation 0x00000001840006e4 0x183ff4000 + 50916
6 Foundation 0x000000018401fafc 0x183ff4000 + 178940
7 UIKit 0x000000018ded9630 0x18d307000 + 12396080
8 Foundation 0x0000000184101860 0x183ff4000 + 1103968
9 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
10 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
11 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 2 name: com.twitter.crashlytics.ios.MachExceptionServer
Thread 2:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 MyApp 0x0000000102cdaad8 CLSMachExceptionServer + 100
3 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
4 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
5 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 3 name: com.apple.NSURLConnectionLoader
Thread 3:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 CFNetwork 0x0000000183d41de0 0x183c93000 + 716256
6 Foundation 0x0000000184101860 0x183ff4000 + 1103968
7 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
8 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
9 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 4 name: AVAudioSession Notify Thread
Thread 4:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 AVFAudio 0x0000000189615774 0x189591000 + 542580
6 AVFAudio 0x0000000189640018 0x189591000 + 716824
7 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
8 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
9 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 5:
0 libsystem_kernel.dylib 0x0000000183229150 0x183208000 + 135504
1 libsystem_pthread.dylib 0x000000018333ed30 0x18333a000 + 19760
2 libc++.1.dylib 0x00000001828e3ea4 0x1828dc000 + 32420
3 JavaScriptCore 0x000000018b157d00 0x18a812000 + 9723136
4 JavaScriptCore 0x000000018b157c28 0x18a812000 + 9722920
5 JavaScriptCore 0x000000018b157f8c 0x18a812000 + 9723788
6 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
7 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
8 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 6 name: WebThread
Thread 6:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 WebCore 0x000000018bc1c75c 0x18bbdb000 + 268124
6 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
7 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
8 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 7 name: WebCore: LocalStorage
Thread 7:
0 libsystem_kernel.dylib 0x0000000183229150 0x183208000 + 135504
1 libsystem_pthread.dylib 0x000000018333ed30 0x18333a000 + 19760
2 JavaScriptCore 0x000000018a81fa18 0x18a812000 + 55832
3 JavaScriptCore 0x000000018b13da04 0x18a812000 + 9615876
4 WebKitLegacy 0x000000018d00f5fc 0x18cf7c000 + 603644
5 WebKitLegacy 0x000000018d01226c 0x18cf7c000 + 615020
6 WebKitLegacy 0x000000018d011998 0x18cf7c000 + 612760
7 JavaScriptCore 0x000000018a81c010 0x18a812000 + 40976
8 JavaScriptCore 0x000000018a81bf50 0x18a812000 + 40784
9 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
10 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
11 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 8 name: com.apple.CFSocket.private
Thread 8:
0 libsystem_kernel.dylib 0x0000000183229570 0x183208000 + 136560
1 CoreFoundation 0x00000001836c2184 0x1835d0000 + 991620
2 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
3 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
4 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 9:
0 libsystem_pthread.dylib 0x000000018333ac1c 0x18333a000 + 3100
Thread 10:
0 libsystem_kernel.dylib 0x0000000183229dbc 0x183208000 + 138684
1 libsystem_pthread.dylib 0x000000018333afa0 0x18333a000 + 4000
2 libsystem_pthread.dylib 0x000000018333ac20 0x18333a000 + 3104
Thread 11:
0 libsystem_pthread.dylib 0x000000018333ac1c 0x18333a000 + 3100
Thread 0 crashed with ARM Thread State (64-bit):
x0: 0x0000000010004005 x1: 0x0000000007000806 x2: 0x0000000000000000 x3: 0x0000000000000c00
x4: 0x0000000000002b03 x5: 0x00000000ffffffff x6: 0x0000000000000000 x7: 0x0000000000000000
x8: 0x00000000fffffbbf x9: 0x0000000007000000 x10: 0x0000000007000100 x11: 0x0000000000000040
x12: 0xffffffffffffffff x13: 0x0000000000000001 x14: 0x01e8540001e85400 x15: 0x0000000000000000
x16: 0xffffffffffffffe1 x17: 0x00000000ffffffff x18: 0x0000000000000000 x19: 0x0000000000000000
x20: 0x00000000ffffffff x21: 0x0000000000002b03 x22: 0x0000000000000c00 x23: 0x000000016d3aed38
x24: 0x0000000007000806 x25: 0x0000000000000000 x26: 0x0000000007000806 x27: 0x0000000000000c00
x28: 0x0000000000000001 fp: 0x000000016d3aec30 lr: 0x0000000183208a3c
sp: 0x000000016d3aebe0 pc: 0x0000000183208bc4 cpsr: 0x60000000
我的代码中唯一 运行 的部分是 main.m，第 22 行，即
int retVal = UIApplicationMain(argc, argv, nil, @"PSSMyAppDelegate");
因此，我对我的应用程序如何因 运行 时间违规而反复被杀死感到困惑，而实际上我的代码 none 似乎是 运行 . iOS 11 中有什么新内容可以改变看门狗进程的行为吗？如果不是，我如何判断我的代码的哪一部分是违反 运行 太久的部分？
您的线程 0 看起来很像我们在 iOS11 中遇到的崩溃。这是我们的：
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x00000001853c4bc4 mach_msg_trap + 8
1 libsystem_kernel.dylib 0x00000001853c4a3c mach_msg + 72
2 CoreFoundation 0x0000000185875c4c __CFRunLoopServiceMachPort + 196
3 CoreFoundation 0x0000000185873818 __CFRunLoopRun + 1424
4 CoreFoundation 0x0000000185793e78 CFRunLoopRunSpecific + 436
5 GraphicsServices 0x0000000187628f84 GSEventRunModal + 100
6 UIKit 0x000000018f5360bc UIApplicationMain + 208
7 TestCrashInBackground 0x0000000100e8dbac 0x100e88000 + 23468
8 libdyld.dylib 0x00000001852b656c start + 4
对我们来说，问题是显示通知会导致应用程序崩溃（当应用程序处于后台时）。我们甚至创建了一个测试应用程序（您在上面看到的 TestCrashInBackground），我们可以在其中重现此问题。该应用程序仅显示通知，没有任何后台任务。
测试用例为：
- 应用显示通知
- 用户将应用设置为后台（按主页键）。
- 用户锁屏
结果：OS 会在（短）时间后终止应用程序。
发生这种情况后，我们进行了系统诊断，我们可以看到，当我们显示通知时，添加了一个名为 "will present notification" 的断言。
default 2017-10-03 14:32:16.280562 +0200 assertiond [SpringBoard:53] Attempting to acquire assertion for TestCrashInBack:507: <BKProcessAssertion: 0x101235c90; "will present notification" (notificationAction:30s); id:…E1D79D51D1D9>
default 2017-10-03 14:32:16.281283 +0200 assertiond [TestCrashInBack:507] Add assertion: <BKProcessAssertion: 0x101235c90; id: 53-96A5F4EA-4C42-4675-97E4-E1D79D51D1D9; name: "will present notification"; state: active; reason: notificationAction; duration: 30.0s> {
owner = <BSProcessHandle: 0x10110a810; SpringBoard:53; valid: YES>;
flags = preventSuspend, preventThrottleDownUI, preventIdleSleep, preventSuspendOnSleep;
}
大约 45 秒后应用程序被终止，因为它 "has active assertions beyond permitted time":
default 2017-10-03 14:33:00.436085 +0200 assertiond [TestCrashInBack:507] Forcing crash report with description: TestCrashInBack:507 has active assertions beyond permitted time:
<BKProcessAssertion: 0x101235c90; "will present notification" (notificationAction:30s); id:…E1D79D51D1D9> (owner: SpringBoard:53)
所有这些只是为了显示通知...非常严重的错误！
这是添加通知的代码：
UNMutableNotificationContent *content = [[UNMutableNotificationContent alloc] init];
content.body = NSLocalizedString(@"This is test notification", nil);
UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:content.body content:content trigger:[UNTimeIntervalNotificationTrigger triggerWithTimeInterval:1.0 repeats:NO]];
[[UNUserNotificationCenter currentNotificationCenter] addNotificationRequest:request withCompletionHandler:^(NSError * _Nullable error) {
NSLog(@"display notification error:%@", error);
}];
我已经向 Apple (id: 34788843) 提交了一份错误报告，其中包含我们的测试项目和所附的 sysdiagnose。希望他们能尽快解决这个问题。
我与 Apple 的一位工程师进行了交谈，他对问题的描述如下 --
想象我们有这样的方法：
- (void)startTask {
self.bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask:self.bgTask];
self.bgTask = UIBackgroundTaskInvalid;
}];
}
代码然后调用它两次（比如，因为我们收到了两次对 didReceiveRemoteNotification 的调用）：
[self startTask];
[self startTask];
根据我们采访过的工程师的说法，应用程序将完全按照我们所看到的方式崩溃。
此外，从技术上讲，只要我们在结束第一个任务之前创建第二个任务，我们的应用就会崩溃。除非后台任务直接附加到直接管理其生命周期并且不能 "owning" 多个的其他对象（例如，独立操作在创建时开始 1 个任务并在 completion/destruction 结束） )，很难避免 "task reentrancy" 问题。
更好的选择是在任务过期时依赖局部变量，让您的对象成员变量远离过期处理程序。
我正在调试用户报告我们的应用程序从 iOS11 开始在后台反复退出，即使在活跃使用期间（例如，用户在几秒钟内将我们和 returns 置于后台或一分钟，才发现它重新启动了）。崩溃日志都揭示了相同的原因：看门狗超时。以下是此类崩溃日志中的相关内容：
Exception Type: EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Reason: Namespace <0xF>, Code 0x8badf00d
Triggered by Thread: 0
我意识到我们的代码在接收推送通知或后台运行时的运行时间有限。我们确实使用 UIBackgroundTasks（使用 Alamofire Networking，FWIW），并且我们确实有执行此操作的过期处理程序：
backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask:backgroundTask];
backgroundTask = UIBackgroundTaskInvalid; // Set the task to be invalid
DebugLog(@"Ended because expiration");
}];
关于这些崩溃报告最令人费解的是我们的代码不在堆栈中。从 this Apple discussion of the 0x8badf00d exception code 可以看出，违规代码实际上是在主线程上主动执行的。
但是，在我的例子中，none 的堆栈曾经执行过我的任何代码。这是一个有代表性的样本：
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 GraphicsServices 0x000000018546cf84 0x185462000 + 44932
6 UIKit 0x000000018d37a0bc 0x18d307000 + 471228
7 MyApp 0x0000000102a6572c main + 87852 (main.m:22)
8 libdyld.dylib 0x00000001830fa56c 0x1830f9000 + 5484
Thread 1 name: com.apple.uikit.eventfetch-thread
Thread 1:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 Foundation 0x00000001840006e4 0x183ff4000 + 50916
6 Foundation 0x000000018401fafc 0x183ff4000 + 178940
7 UIKit 0x000000018ded9630 0x18d307000 + 12396080
8 Foundation 0x0000000184101860 0x183ff4000 + 1103968
9 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
10 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
11 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 2 name: com.twitter.crashlytics.ios.MachExceptionServer
Thread 2:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 MyApp 0x0000000102cdaad8 CLSMachExceptionServer + 100
3 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
4 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
5 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 3 name: com.apple.NSURLConnectionLoader
Thread 3:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 CFNetwork 0x0000000183d41de0 0x183c93000 + 716256
6 Foundation 0x0000000184101860 0x183ff4000 + 1103968
7 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
8 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
9 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 4 name: AVAudioSession Notify Thread
Thread 4:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 AVFAudio 0x0000000189615774 0x189591000 + 542580
6 AVFAudio 0x0000000189640018 0x189591000 + 716824
7 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
8 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
9 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 5:
0 libsystem_kernel.dylib 0x0000000183229150 0x183208000 + 135504
1 libsystem_pthread.dylib 0x000000018333ed30 0x18333a000 + 19760
2 libc++.1.dylib 0x00000001828e3ea4 0x1828dc000 + 32420
3 JavaScriptCore 0x000000018b157d00 0x18a812000 + 9723136
4 JavaScriptCore 0x000000018b157c28 0x18a812000 + 9722920
5 JavaScriptCore 0x000000018b157f8c 0x18a812000 + 9723788
6 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
7 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
8 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 6 name: WebThread
Thread 6:
0 libsystem_kernel.dylib 0x0000000183208bc4 0x183208000 + 3012
1 libsystem_kernel.dylib 0x0000000183208a3c 0x183208000 + 2620
2 CoreFoundation 0x00000001836b9c4c 0x1835d0000 + 957516
3 CoreFoundation 0x00000001836b7818 0x1835d0000 + 948248
4 CoreFoundation 0x00000001835d7e78 0x1835d0000 + 32376
5 WebCore 0x000000018bc1c75c 0x18bbdb000 + 268124
6 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
7 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
8 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 7 name: WebCore: LocalStorage
Thread 7:
0 libsystem_kernel.dylib 0x0000000183229150 0x183208000 + 135504
1 libsystem_pthread.dylib 0x000000018333ed30 0x18333a000 + 19760
2 JavaScriptCore 0x000000018a81fa18 0x18a812000 + 55832
3 JavaScriptCore 0x000000018b13da04 0x18a812000 + 9615876
4 WebKitLegacy 0x000000018d00f5fc 0x18cf7c000 + 603644
5 WebKitLegacy 0x000000018d01226c 0x18cf7c000 + 615020
6 WebKitLegacy 0x000000018d011998 0x18cf7c000 + 612760
7 JavaScriptCore 0x000000018a81c010 0x18a812000 + 40976
8 JavaScriptCore 0x000000018a81bf50 0x18a812000 + 40784
9 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
10 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
11 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 8 name: com.apple.CFSocket.private
Thread 8:
0 libsystem_kernel.dylib 0x0000000183229570 0x183208000 + 136560
1 CoreFoundation 0x00000001836c2184 0x1835d0000 + 991620
2 libsystem_pthread.dylib 0x000000018333c31c 0x18333a000 + 8988
3 libsystem_pthread.dylib 0x000000018333c1e8 0x18333a000 + 8680
4 libsystem_pthread.dylib 0x000000018333ac28 0x18333a000 + 3112
Thread 9:
0 libsystem_pthread.dylib 0x000000018333ac1c 0x18333a000 + 3100
Thread 10:
0 libsystem_kernel.dylib 0x0000000183229dbc 0x183208000 + 138684
1 libsystem_pthread.dylib 0x000000018333afa0 0x18333a000 + 4000
2 libsystem_pthread.dylib 0x000000018333ac20 0x18333a000 + 3104
Thread 11:
0 libsystem_pthread.dylib 0x000000018333ac1c 0x18333a000 + 3100
Thread 0 crashed with ARM Thread State (64-bit):
x0: 0x0000000010004005 x1: 0x0000000007000806 x2: 0x0000000000000000 x3: 0x0000000000000c00
x4: 0x0000000000002b03 x5: 0x00000000ffffffff x6: 0x0000000000000000 x7: 0x0000000000000000
x8: 0x00000000fffffbbf x9: 0x0000000007000000 x10: 0x0000000007000100 x11: 0x0000000000000040
x12: 0xffffffffffffffff x13: 0x0000000000000001 x14: 0x01e8540001e85400 x15: 0x0000000000000000
x16: 0xffffffffffffffe1 x17: 0x00000000ffffffff x18: 0x0000000000000000 x19: 0x0000000000000000
x20: 0x00000000ffffffff x21: 0x0000000000002b03 x22: 0x0000000000000c00 x23: 0x000000016d3aed38
x24: 0x0000000007000806 x25: 0x0000000000000000 x26: 0x0000000007000806 x27: 0x0000000000000c00
x28: 0x0000000000000001 fp: 0x000000016d3aec30 lr: 0x0000000183208a3c
sp: 0x000000016d3aebe0 pc: 0x0000000183208bc4 cpsr: 0x60000000
我的代码中唯一 运行 的部分是 main.m，第 22 行，即
int retVal = UIApplicationMain(argc, argv, nil, @"PSSMyAppDelegate");
因此，我对我的应用程序如何因 运行 时间违规而反复被杀死感到困惑，而实际上我的代码 none 似乎是 运行 . iOS 11 中有什么新内容可以改变看门狗进程的行为吗？如果不是，我如何判断我的代码的哪一部分是违反 运行 太久的部分？
您的线程 0 看起来很像我们在 iOS11 中遇到的崩溃。这是我们的：
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 libsystem_kernel.dylib 0x00000001853c4bc4 mach_msg_trap + 8
1 libsystem_kernel.dylib 0x00000001853c4a3c mach_msg + 72
2 CoreFoundation 0x0000000185875c4c __CFRunLoopServiceMachPort + 196
3 CoreFoundation 0x0000000185873818 __CFRunLoopRun + 1424
4 CoreFoundation 0x0000000185793e78 CFRunLoopRunSpecific + 436
5 GraphicsServices 0x0000000187628f84 GSEventRunModal + 100
6 UIKit 0x000000018f5360bc UIApplicationMain + 208
7 TestCrashInBackground 0x0000000100e8dbac 0x100e88000 + 23468
8 libdyld.dylib 0x00000001852b656c start + 4
对我们来说，问题是显示通知会导致应用程序崩溃（当应用程序处于后台时）。我们甚至创建了一个测试应用程序（您在上面看到的 TestCrashInBackground），我们可以在其中重现此问题。该应用程序仅显示通知，没有任何后台任务。 测试用例为：
- 应用显示通知
- 用户将应用设置为后台（按主页键）。
- 用户锁屏
结果：OS 会在（短）时间后终止应用程序。
发生这种情况后，我们进行了系统诊断，我们可以看到，当我们显示通知时，添加了一个名为 "will present notification" 的断言。
default 2017-10-03 14:32:16.280562 +0200 assertiond [SpringBoard:53] Attempting to acquire assertion for TestCrashInBack:507: <BKProcessAssertion: 0x101235c90; "will present notification" (notificationAction:30s); id:…E1D79D51D1D9>
default 2017-10-03 14:32:16.281283 +0200 assertiond [TestCrashInBack:507] Add assertion: <BKProcessAssertion: 0x101235c90; id: 53-96A5F4EA-4C42-4675-97E4-E1D79D51D1D9; name: "will present notification"; state: active; reason: notificationAction; duration: 30.0s> {
owner = <BSProcessHandle: 0x10110a810; SpringBoard:53; valid: YES>;
flags = preventSuspend, preventThrottleDownUI, preventIdleSleep, preventSuspendOnSleep;
}
大约 45 秒后应用程序被终止，因为它 "has active assertions beyond permitted time":
default 2017-10-03 14:33:00.436085 +0200 assertiond [TestCrashInBack:507] Forcing crash report with description: TestCrashInBack:507 has active assertions beyond permitted time:
<BKProcessAssertion: 0x101235c90; "will present notification" (notificationAction:30s); id:…E1D79D51D1D9> (owner: SpringBoard:53)
所有这些只是为了显示通知...非常严重的错误！
这是添加通知的代码：
UNMutableNotificationContent *content = [[UNMutableNotificationContent alloc] init];
content.body = NSLocalizedString(@"This is test notification", nil);
UNNotificationRequest *request = [UNNotificationRequest requestWithIdentifier:content.body content:content trigger:[UNTimeIntervalNotificationTrigger triggerWithTimeInterval:1.0 repeats:NO]];
[[UNUserNotificationCenter currentNotificationCenter] addNotificationRequest:request withCompletionHandler:^(NSError * _Nullable error) {
NSLog(@"display notification error:%@", error);
}];
我已经向 Apple (id: 34788843) 提交了一份错误报告，其中包含我们的测试项目和所附的 sysdiagnose。希望他们能尽快解决这个问题。
我与 Apple 的一位工程师进行了交谈，他对问题的描述如下 -- 想象我们有这样的方法：
- (void)startTask {
self.bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
[application endBackgroundTask:self.bgTask];
self.bgTask = UIBackgroundTaskInvalid;
}];
}
代码然后调用它两次（比如，因为我们收到了两次对 didReceiveRemoteNotification 的调用）：
[self startTask];
[self startTask];
根据我们采访过的工程师的说法，应用程序将完全按照我们所看到的方式崩溃。
此外，从技术上讲，只要我们在结束第一个任务之前创建第二个任务，我们的应用就会崩溃。除非后台任务直接附加到直接管理其生命周期并且不能 "owning" 多个的其他对象（例如，独立操作在创建时开始 1 个任务并在 completion/destruction 结束） )，很难避免 "task reentrancy" 问题。
更好的选择是在任务过期时依赖局部变量，让您的对象成员变量远离过期处理程序。