@synchronized(self) 加锁引起的Crash

一、最近米家App进入前台的时候上报上来一个Crash

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{"app_name":"MiHome","timestamp":"2019-04-03 11:00:09.66 +0800","app_version":"4.15.101","slice_uuid":"d41578a2-af0f-3fc5-b202-c120aeaacba2","adam_id":0,"build_version":"4.15.101.1334","bundleID":"com.xiaomi.mihome.dailybuild","share_with_app_devs":false,"is_first_party":false,"bug_type":"109","os_version":"iPhone OS 12.1 (16B92)","incident_id":"0DD1416C-EFFC-45CC-A5B1-7099FD5582E1","name":"MiHome"} Incident Identifier: 0DD1416C-EFFC-45CC-A5B1-7099FD5582E1 CrashReporter Key:   0d34987d160e2a213f0eea4224c7be37b0e5f7ff Hardware Model:      iPhone10,2 Process:             MiHome [12041] Path:                /private/var/containers/Bundle/Application/C164FC42-7011-4900-B31D-C1FBF97A4927/MiHome.app/MiHome Identifier:          com.xiaomi.mihome.dailybuild Version:             4.15.101.1334 (4.15.101) AppStoreTools:       10B61 Code Type:           ARM-64 (Native) Role:                Non UI Parent Process:      launchd [1] Coalition:           com.xiaomi.mihome.dailybuild [15486]     Date/Time:           2019-04-03 11:00:09.4286 +0800 Launch Time:         2019-04-03 10:56:55.4746 +0800 OS Version:          iPhone OS 12.1 (16B92) Baseband Version:    3.11.00 Report Version:      104   Exception Type:  EXC_CRASH (SIGKILL) Exception Codes: 0x0000000000000000, 0x0000000000000000 Exception Note:  EXC_CORPSE_NOTIFY Termination Reason: Namespace SPRINGBOARD, Code 0x8badf00d Termination Description: SPRINGBOARD, scene-update watchdog transgression: com.xiaomi.mihome.dailybuild exhausted real (wall clock) time allowance of 10.00 seconds | ProcessVisibility: Foreground | ProcessState: Running | WatchdogEvent: scene-update | WatchdogVisibility: Foreground | WatchdogCPUStatistics: ( | "Elapsed total CPU time (seconds): 3.890 (user 3.890, system 0.000), 6% CPU", | "Elapsed application CPU time (seconds): 0.695, 1% CPU" | ) Triggered by Thread:  0   Thread 0 name:  Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0   libsystem_kernel.dylib          0x00000001c97a79fc __ulock_wait + 8 1   libsystem_platform.dylib        0x00000001c981b8f8 _os_unfair_lock_lock_slow + 172 2   libobjc.A.dylib                 0x00000001c8df4830 objc_sync_enter + 32 3   MiHome                          0x00000001035add48 -[MHTutkIotcManager registerNotifDictString] + 22076744 (MHTutkIotcManager.m:286) 4   MiHome                          0x00000001035ad654 -[MHTutkIotcManager appEnterForeground:] + 22074964 (MHTutkIotcManager.m:241) 5   MiHome                          0x0000000104b22c8c __43-[MHNotificationCenter processNotificaton:]_block_invoke + 44575884 (MHNotificationCenter.m:162) 6   CoreFoundation                  0x00000001c9af56bc -[__NSArrayM enumerateObjectsWithOptions:usingBlock:] + 216 7   MiHome                          0x0000000104b22b6c -[MHNotificationCenter processNotificaton:] + 44575596 (MHNotificationCenter.m:164) 8   CoreFoundation                  0x00000001c9b7e928 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 20 9   CoreFoundation                  0x00000001c9b7e8f4 ___CFXRegistrationPost_block_invoke + 64 10  CoreFoundation                  0x00000001c9b7dde4 _CFXRegistrationPost + 392 11  CoreFoundation                  0x00000001c9b7da90 ___CFXNotificationPost_block_invoke + 96 12  CoreFoundation                  0x00000001c9af5d70 -[_CFXNotificationRegistrar find:object:observer:enumerator:] + 1404 13  CoreFoundation                  0x00000001c9b7d51c _CFXNotificationPost + 696 14  Foundation                      0x00000001ca58dc10 -[NSNotificationCenter postNotificationName:object:userInfo:] + 68 15  UIKitCore                       0x00000001f6e29c30 -[UIApplication _sendWillEnterForegroundCallbacks] + 232 16  UIKitCore                       0x00000001f66abdc4 -[__UICanvasLifecycleMonitor_Compatability activateEventsOnly:withContext:completion:] + 2180 17  UIKitCore                       0x00000001f66a9a74 __82-[_UIApplicationCanvas _transitionLifecycleStateWithTransitionContext:completion:]_block_invoke + 772 18  UIKitCore                       0x00000001f66a9720 -[_UIApplicationCanvas _transitionLifecycleStateWithTransitionContext:completion:] + 432 19  UIKitCore                       0x00000001f66ae8e0 __125-[_UICanvasLifecycleSettingsDiffAction performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:]_block_invoke + 220 20  UIKitCore                       0x00000001f66af840 _performActionsWithDelayForTransitionContext + 112 21  UIKitCore                       0x00000001f66ae798 -[_UICanvasLifecycleSettingsDiffAction performActionsForCanvas:withUpdatedScene:settingsDiff:fromSettings:transitionContext:] + 248 22  UIKitCore                       0x00000001f66b3684 -[_UICanvas scene:didUpdateWithDiff:transitionContext:completion:] + 368 23  UIKitCore                       0x00000001f69f7090 -[UIApplicationSceneClientAgent scene:handleEvent:withCompletion:] + 468 24  FrontBoardServices              0x00000001cc6456e4 __80-[FBSSceneImpl updater:didUpdateSettings:withDiff:transitionContext:completion:]_block_invoke.359 + 228 25  libdispatch.dylib               0x00000001c964a484 _dispatch_client_callout + 16 26  libdispatch.dylib               0x00000001c96213f0 _dispatch_block_invoke_direct$VARIANT$armv81 + 216 27  FrontBoardServices              0x00000001cc683a9c __FBSSERIALQUEUE_IS_CALLING_OUT_TO_A_BLOCK__ + 40 28  FrontBoardServices              0x00000001cc683728 -[FBSSerialQueue _performNext] + 416 29  FrontBoardServices              0x00000001cc683d44 -[FBSSerialQueue _performNextFromRunLoopSource] + 56 30  CoreFoundation                  0x00000001c9ba01cc __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 24 31  CoreFoundation                  0x00000001c9ba014c __CFRunLoopDoSource0 + 88 32  CoreFoundation                  0x00000001c9b9fa30 __CFRunLoopDoSources0 + 176 33  CoreFoundation                  0x00000001c9b9a8fc __CFRunLoopRun + 1040 34  CoreFoundation                  0x00000001c9b9a1cc CFRunLoopRunSpecific + 436 35  GraphicsServices                0x00000001cbe11584 GSEventRunModal + 100 36  UIKitCore                       0x00000001f6e11054 UIApplicationMain + 212 37  MiHome                          0x00000001026e9a00 main + 6593024 (main.m:19) 38  libdyld.dylib                   0x00000001c965abb4 start + 4   Thread 28 name:  Dispatch queue: com.apple.root.default-qos Thread 28: 0   libsystem_kernel.dylib          0x00000001c97a7428 __semwait_signal + 8 1   libsystem_c.dylib               0x00000001c971c5d0 nanosleep + 212 2   libsystem_c.dylib               0x00000001c971c4a4 usleep + 64 3   MiHome                          0x00000001027a1d50 IOTC_Connect_UDP + 7347536 (UDP_Connect.c:2410) 4   MiHome                          0x00000001035ac59c -[MHTutkIotcManager mh_iotcConnectByUIDParallel:uId:sId:] + 22070684 (MHTutkIotcManager.m:129) 5   MiHome                          0x00000001035b28d0 __63-[MHTUTKP2PConnection connectIOTCDeviceWithUId:did:completion:]_block_invoke + 22096080 (MHTUTKP2PConnection.m:533) 6   libdispatch.dylib               0x00000001c96496c8 _dispatch_call_block_and_release + 24 7   libdispatch.dylib               0x00000001c964a484 _dispatch_client_callout + 16 8   libdispatch.dylib               0x00000001c9620a7c _dispatch_queue_override_invoke + 664 9   libdispatch.dylib               0x00000001c962cafc _dispatch_root_queue_drain + 344 10  libdispatch.dylib               0x00000001c962d35c _dispatch_worker_thread2 + 116 11  libsystem_pthread.dylib         0x00000001c982c17c _pthread_wqthread + 472 12  libsystem_pthread.dylib         0x00000001c982ecec start_wqthread + 4

从Crash类型可以查询出来，Termination Reason: Namespace SPRINGBOARD, Code 0x8badf00d 代表主线程无响应，被watchdog杀掉了

主线程被阻塞，无非几种原因、死锁，方法执行耗时过长。

查询主线程，确实发现@synchronized(self) 加锁了，并且也是等锁导致等时间过长。子线程等方法中 使用了@synchronized加锁，内部操作长时间不返回，导致主线程被阻塞。

 

总结：

所有关于加锁的，一定要考虑加锁的粒度，同时考虑等锁等是不是主线程。

耗时过长的操作，设计线程安全的，可以放在队列中，使用队列解决。