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iOS11看門狗超時崩潰(0x8badf00d)但代碼不在堆棧上

[英]iOS11 watchdog timeout crashes (0x8badf00d) but code not on stack

我正在調試我們的應用程序的用戶報告,這些報告在iOS11開始時在后台重復退出,即使在活動使用期間(例如,用戶背景我們並在幾秒鍾或一分鍾內返回,只是發現它重新啟動)。 崩潰日志都顯示了相同的原因:看門狗超時。 以下是一個此類崩潰日志中的相關位:

Exception Type:  EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Termination Reason: Namespace <0xF>, Code 0x8badf00d
Triggered by Thread:  0

我意識到我們的代碼在接收推送通知或后台運行時的操作時間有限。 我們肯定使用UIBackgroundTasks(使用Alamofire Networking ,FWIW),我們確實有過期處理程序執行此操作:

backgroundTask = [application beginBackgroundTaskWithExpirationHandler:^{
    [application endBackgroundTask:backgroundTask];
    backgroundTask = UIBackgroundTaskInvalid; // Set the task to be invalid
    DebugLog(@"Ended because expiration");
}];

關於這些崩潰報告最令人困惑的事情是我們的代碼無處於堆棧中。 我們可以從Apple對0x8badf00d異常代碼的討論中看到,實際上,有問題的代碼正在主線程上主動執行。

但是,在我的情況下,沒有任何堆棧有任何代碼被執行。 這是一個代表性的樣本:

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

我運行的代碼的唯一部分是main.m,第22行,即

int retVal = UIApplicationMain(argc, argv, nil, @"PSSMyAppDelegate");  

因此,當我的代碼似乎沒有運行時,我很困惑我的應用程序如何被重復殺死以防止運行時違規。 iOS 11中有什么新東西可以改變看門狗進程的行為嗎? 如果沒有,我如何判斷我的代碼的哪一部分是違反運行時間過長的部分?

你的線程0看起來很像我們在iOS 11中遇到的崩潰。這是我們的:

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

對我們來說問題是顯示通知會導致應用程序崩潰(當應用程序背景化時)。 我們甚至創建了一個測試應用程序(您在上面看到的TestCrashInBackground),我們可以在其中重現此問題。 該應用程序僅顯示通知,並且沒有任何后台任務。 測試用例是:

  1. 該應用程序顯示通知
  2. 用戶為應用程序添加背景(按下主頁鍵)。
  3. 用戶鎖定屏幕

結果:操作系統在一段(短)時間后殺死應用程序。

在發生這種情況之后我們采取了sysdiagnose,我們可以看到,當我們顯示通知時,會添加一個名為“將顯示通知”的斷言。

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;
}

大約45秒后,該應用程序被殺死,因為它“超出允許時間有活動斷言”:

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)

這一切只是為了顯示通知......非常嚴重的錯誤!

這是添加通知的代碼:

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);
}];

我已經向Apple(id:34788843)提交了一個錯誤報告,其中包含我們的測試項目和附帶的sysdiagnose。 希望他們能盡快解決這個問題。

我和Apple的一位工程師交談過,他描述了這個問題如下 - 假設我們有這樣的方法:

- (void)startTask {
   self.bgTask = [application beginBackgroundTaskWithExpirationHandler:^{
      [application endBackgroundTask:self.bgTask];
      self.bgTask = UIBackgroundTaskInvalid;
   }];
}

然后代碼調用它兩次(例如,因為我們收到了兩次對didReceiveRemoteNotification調用):

[self startTask];
[self startTask];

根據我們采訪過的工程師的說法,應用程序將以我們看到的方式完全崩潰。

而且,從技術上講,我們的應用程序會在結束第一個任務之前創建第二個任務時崩潰。 除非后台任務直接附加到直接管理其生命周期的某個其他對象,並且無法“擁有”多個(例如,在創建時開始1個單獨任務並在完成/銷毀時結束它的獨立操作),它非常難以避免“任務重入”問題。

更好的選擇是依賴局部變量來完成任務,保持對象成員變量不在到期處理程序之外。

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