How to fix EXC_CRASH (SIGKILL) watchdog termination?

Question

I am running into a watchdog termination crash. After watching this WWDC session and reading the relevant documentation about watchdog crashes, I suspect there is some kind of deadlock.

But I am unable to understand how my code is causing deadlock. I have removed stack traces of some threads here because of the character limit. The complete crash log can be found in this GitHub gist

Incident Identifier: 5E8D976C-94FC-4400-A729-20BD48E26C7C
Hardware Model:      iPhone13,3
Process:             Fhetch [73637]
Path:                /private/var/containers/Bundle/Application/3581EBF4-AE49-411D-B444-10D2617B1D45/XYZ.app/XYZ
Identifier:          com.XYZ.APP
Version:             1.1.3 (18)
AppStoreTools:       13E500
AppVariant:          1:iPhone13,3:15
Beta:                YES
Code Type:           ARM-64 (Native)
Role:                Foreground
Parent Process:      launchd [1]
Coalition:           com.XYZ.APP [2854]

Date/Time:           2022-04-25 14:04:47.1725 -0400
Launch Time:         2022-04-24 23:09:42.3116 -0400
OS Version:          iPhone OS 15.4.1 (19E258)
Release Type:        User
Baseband Version:    2.53.01
Report Version:      104

Exception Type:  EXC_CRASH (SIGKILL)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Termination Reason: FRONTBOARD 2343432205 
<RBSTerminateContext| domain:10 code:0x8BADF00D explanation:scene-update watchdog transgression: application<com.XYZ.APP>:73637 exhausted real (wall clock) time allowance of 10.00 seconds
ProcessVisibility: Foreground
ProcessState: Running
WatchdogEvent: scene-update
WatchdogVisibility: Background
WatchdogCPUStatistics: (
"Elapsed total CPU time (seconds): 9.260 (user 5.280, system 3.980), 15% CPU",
"Elapsed application CPU time (seconds): 0.101, 0% CPU"
) reportType:CrashLog maxTerminationResistance:Interactive>

Triggered by Thread:  0


Kernel Triage:
VM - Compressor failed a blocking pager_get
VM - Compressor failed a blocking pager_get
VM - Compressor failed a blocking pager_get
VM - Compressor failed a blocking pager_get
VM - Compressor failed a blocking pager_get


Thread 0 name:
Thread 0 Crashed:
0   libsystem_kernel.dylib          0x00000001fcd27bdc kevent_id + 8
1   libdispatch.dylib               0x00000001c4eef1fc _dispatch_kq_poll + 228 (event_kevent.c:750)
2   libdispatch.dylib               0x00000001c4eefc20 _dispatch_event_loop_wait_for_ownership + 444 (event_kevent.c:2209)
3   libdispatch.dylib               0x00000001c4edbf54 __DISPATCH_WAIT_FOR_QUEUE__ + 328 (queue.c:1690)
4   libdispatch.dylib               0x00000001c4edbb28 _dispatch_sync_f_slow + 144 (queue.c:1774)
5   CoreData                        0x00000001cc9bfa94 -[NSManagedObjectContext performBlockAndWait:] + 264 (NSManagedObjectContext.m:4059)
6   FHKit                           0x00000001016c55c0 closure #1 in static FHDataManager.transfer<A>(_:intoContext:) + 1288 (DataManager+ManagedObjects.swift:56)
7   FHKit                           0x000000010166124c thunk for @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
8   FHKit                           0x00000001016612ac thunk for @escaping @callee_guaranteed () -> () + 28 (<compiler-generated>:0)
9   CoreData                        0x00000001cc9bf834 developerSubmittedBlockToNSManagedObjectContextPerform + 156 (NSManagedObjectContext.m:3942)
10  CoreData                        0x00000001cc9bfa5c -[NSManagedObjectContext performBlockAndWait:] + 208 (NSManagedObjectContext.m:4053)
11  FHKit                           0x00000001016c4e98 static FHDataManager.transfer<A>(_:intoContext:) + 576 (DataManager+ManagedObjects.swift:49)
12  FHKit                           0x00000001016c4404 static FHDataManager.transfer<A>(_:intoContext:) + 951300 (DataManager+ManagedObjects.swift:39)
13  FHKit                           0x0000000101776b84 FHIdentifiableEntity.hasSameId<A>(as:) + 596 (IdentifiableEntity.swift:36)
14  FHKit                           0x0000000101698a5c FHSubmittableUserAction.supercedes(_:) + 3012 (SubmittableUserAction.swift:77)
15  FHKit                           0x000000010186c9bc closure #1 in closure #1 in closure #1 in static FHActionManager.process(submittableUserAction:fromContext:) + 112 (ActionManager+Processing.swift:419)
16  FHKit                           0x000000010166124c thunk for @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
17  FHKit                           0x00000001016612ac thunk for @escaping @callee_guaranteed () -> () + 28 (<compiler-generated>:0)
18  CoreData                        0x00000001cc9bf834 developerSubmittedBlockToNSManagedObjectContextPerform + 156 (NSManagedObjectContext.m:3942)
19  CoreData                        0x00000001cc9bfa5c -[NSManagedObjectContext performBlockAndWait:] + 208 (NSManagedObjectContext.m:4053)
20  FHKit                           0x000000010186c818 closure #1 in closure #1 in static FHActionManager.process(submittableUserAction:fromContext:) + 668 (ActionManager+Processing.swift:417)
21  FHKit                           0x00000001019cc734 closure #1 in closure #1 in static FHNetworkOperationsQueue.remove(operationBlockIf:) + 60 (NetworkOperationsQueue.swift:233)
22  FHKit                           0x00000001019cc790 thunk for @callee_guaranteed (@guaranteed FHNetworkOperation) -> (@unowned Bool, @error @owned Error) + 28 (<compiler-generated>:0)
23  FHKit                           0x00000001019cd864 partial apply for thunk for @callee_guaranteed (@guaranteed FHNetworkOperation) -> (@unowned Bool, @error @owned Error) + 32 (<compiler-generated>:0)
24  libswiftCore.dylib              0x00000001c9cbec30 _ArrayProtocol.filter(_:) + 1000 (ArrayType.swift:73)
25  FHKit                           0x00000001019cc698 closure #1 in static FHNetworkOperationsQueue.remove(operationBlockIf:) + 224 (NetworkOperationsQueue.swift:231)
26  FHKit                           0x00000001016ca4b4 thunk for @callee_guaranteed () -> (@error @owned Error) + 24 (<compiler-generated>:0)
27  FHKit                           0x00000001019cd828 thunk for @callee_guaranteed () -> (@error @owned Error)partial apply + 32 (<compiler-generated>:0)
28  FHKit                           0x00000001016cde5c static FHThreadManager.synchronized<A>(_:shouldLogInfo:_:) + 924 (ThreadAndQueueManagement.swift:195)
29  FHKit                           0x00000001016ca460 synchronized<A>(_:shouldLogInfo:_:) + 88 (ThreadAndQueueManagement.swift:211)
30  FHKit                           0x00000001019c7624 static FHNetworkOperationsQueue.remove(operationBlockIf:) + 4109860 (NetworkOperationsQueue.swift:229)
31  FHKit                           0x000000010186c3f0 closure #1 in static FHActionManager.process(submittableUserAction:fromContext:) + 728 (ActionManager+Processing.swift:409)
32  FHKit                           0x00000001016ca4b4 thunk for @callee_guaranteed () -> (@error @owned Error) + 24 (<compiler-generated>:0)
33  FHKit                           0x000000010186c510 partial apply for thunk for @callee_guaranteed () -> (@error @owned Error) + 32 (<compiler-generated>:0)
34  FHKit                           0x00000001016cde5c static FHThreadManager.synchronized<A>(_:shouldLogInfo:_:) + 924 (ThreadAndQueueManagement.swift:195)
35  FHKit                           0x00000001016ca460 synchronized<A>(_:shouldLogInfo:_:) + 88 (ThreadAndQueueManagement.swift:211)
36  FHKit                           0x000000010186c0e4 static FHActionManager.process(submittableUserAction:fromContext:) + 476 (ActionManager+Processing.swift:439)
37  FHKit                           0x0000000101867638 static FHActionManager.process<A>(actionForRecord:fromContext:) + 680 (ActionManager+Processing.swift:390)
38  FHKit                           0x0000000101866e4c static FHActionManager.process(action:forContent:fromContext:bypassingServerInteraction:withTrustedTimestamps:) + 2666060 (ActionManager+Processing.swift:26)
39  Fhetch                          0x00000001006e4088 closure #1 in FHChatTableViewController.ensureMessageIsRead(message:) + 2015368 (ChatTableViewController+CoreData.swift:668)
40  Fhetch                          0x000000010053e2c4 thunk for @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
41  Fhetch                          0x000000010053e324 thunk for @escaping @callee_guaranteed () -> () + 28 (<compiler-generated>:0)
42  CoreData                        0x00000001cc9bf834 developerSubmittedBlockToNSManagedObjectContextPerform + 156 (NSManagedObjectContext.m:3942)
43  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
44  libdispatch.dylib               0x00000001c4edbc90 _dispatch_lane_barrier_sync_invoke_and_complete + 56 (queue.c:1028)
45  CoreData                        0x00000001cc9bfa94 -[NSManagedObjectContext performBlockAndWait:] + 264 (NSManagedObjectContext.m:4059)
46  Fhetch                          0x00000001006df868 FHChatTableViewController.ensureMessageIsRead(message:) + 1032 (ChatTableViewController+CoreData.swift:658)
47  Fhetch                          0x00000001006dc9d0 closure #1 in FHChatTableViewController.directlyInsertRows(for:reloadTable:resortTable:) + 3640 (ChatTableViewController+CoreData.swift:315)
48  Fhetch                          0x00000001006e0730 thunk for @callee_guaranteed (@guaranteed FHContentMO) -> (@owned FHChatCellContentData?, @error @owned Error) + 2000688 (<compiler-generated>:0)
49  Fhetch                          0x00000001006e4a28 partial apply for thunk for @callee_guaranteed (@guaranteed FHContentMO) -> (@owned FHChatCellContentData?, @error @owned Error) + 2017832 (<compiler-generated>:0)
50  libswiftCore.dylib              0x00000001c9e48ce0 Sequence.compactMap<A>(_:) + 1224 (SequenceAlgorithms.swift:807)
51  Fhetch                          0x00000001006db6ac FHChatTableViewController.directlyInsertRows(for:reloadTable:resortTable:) + 276 (ChatTableViewController+CoreData.swift:289)
52  Fhetch                          0x00000001006d80b8 FHChatTableViewController.updateRows(for:) + 1448 (ChatTableViewController+CoreData.swift:568)
53  Fhetch                          0x00000001006d6ae8 FHChatTableViewController.processCoreDataNotification(_:) + 7964 (ChatTableViewController+CoreData.swift:108)
54  Fhetch                          0x00000001006d45ac closure #1 in FHChatTableViewController.setupCoreDataNotifications() + 1588 (ChatTableViewController+CoreData.swift:38)
55  Fhetch                          0x00000001005d8360 thunk for @escaping @callee_guaranteed (@in_guaranteed Notification) -> () + 918368 (<compiler-generated>:0)
56  Foundation                      0x00000001c69ee564 -[__NSObserver _doit:] + 348 (NSNotification.m:327)
57  CoreFoundation                  0x00000001c51f7324 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 28 (CFNotificationCenter.c:652)
58  CoreFoundation                  0x00000001c5293ac4 ___CFXRegistrationPost_block_invoke + 52 (CFNotificationCenter.c:173)
59  CoreFoundation                  0x00000001c5266cc0 _CFXRegistrationPost + 456 (CFNotificationCenter.c:199)
60  CoreFoundation                  0x00000001c520d39c _CFXNotificationPost + 728 (CFNotificationCenter.c:1147)
61  Foundation                      0x00000001c69d4704 -[NSNotificationCenter postNotificationName:object:userInfo:] + 96 (NSNotification.m:560)
62  CoreData                        0x00000001cc9e2628 -[NSManagedObjectContext _postObjectsDidChangeNotificationWithUserInfo:] + 468 (NSManagedObjectContext.m:8290)
63  CoreData                        0x00000001cc9c87e4 -[NSManagedObjectContext _createAndPostChangeNotification:deletions:updates:refreshes:deferrals:wasMerge:] + 1576 (NSManagedObjectContext.m:7922)
64  CoreData                        0x00000001cc9bfbbc -[NSManagedObjectContext _postRefreshedObjectsNotificationAndClearList] + 200 (NSManagedObjectContext.m:7471)
65  CoreData                        0x00000001cc9be278 -[NSManagedObjectContext _processRecentChanges:] + 108 (NSManagedObjectContext.m:7550)
66  CoreData                        0x00000001cc9bf8b0 developerSubmittedBlockToNSManagedObjectContextPerform + 280 (NSManagedObjectContext.m:3949)
67  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
68  libdispatch.dylib               0x00000001c4edaf48 _dispatch_main_queue_drain + 928 (inline_internal.h:2622)
69  libdispatch.dylib               0x00000001c4edab98 _dispatch_main_queue_callback_4CF + 44 (queue.c:7770)
70  CoreFoundation                  0x00000001c521e2f0 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 16 (CFRunLoop.c:1795)
71  CoreFoundation                  0x00000001c51d81f4 __CFRunLoopRun + 2532 (CFRunLoop.c:3144)
72  CoreFoundation                  0x00000001c51eb6b8 CFRunLoopRunSpecific + 600 (CFRunLoop.c:3268)
73  GraphicsServices                0x00000001e1285374 GSEventRunModal + 164 (GSEvent.c:2200)
74  UIKitCore                       0x00000001c7b50e88 -[UIApplication _run] + 1100 (UIApplication.m:3511)
75  UIKitCore                       0x00000001c78d25ec UIApplicationMain + 364 (UIApplication.m:5064)
76  Fhetch                          0x00000001005ca818 main + 64 (AppDelegate.swift:31)
77  dyld                            0x0000000100fc1ce4 start + 520 (dyldMain.cpp:879)


Thread 7 name:
Thread 7:
0   libsystem_kernel.dylib          0x00000001fcd281a4 select$DARWIN_EXTSN + 8
1   CoreFoundation                  0x00000001c5277658 __CFSocketManager + 644 (CFSocket.c:1343)
2   libsystem_pthread.dylib         0x00000002369969ac _pthread_start + 148 (pthread.c:891)
3   libsystem_pthread.dylib         0x0000000236995e68 thread_start + 8


Thread 9 name:
Thread 9:
0   libsystem_kernel.dylib          0x00000001fcd28178 __ulock_wait + 8
1   libsystem_platform.dylib        0x000000023698d9ac _os_unfair_lock_lock_slow + 172 (lock.c:578)
2   FHKit                           0x00000001016ccad8 lock(_:) + 648 (ThreadAndQueueManagement.swift:144)
3   FHKit                           0x00000001016cde20 static FHThreadManager.synchronized<A>(_:shouldLogInfo:_:) + 864 (ThreadAndQueueManagement.swift:192)
4   FHKit                           0x00000001016ca460 synchronized<A>(_:shouldLogInfo:_:) + 88 (ThreadAndQueueManagement.swift:211)
5   FHKit                           0x000000010186c0e4 static FHActionManager.process(submittableUserAction:fromContext:) + 476 (ActionManager+Processing.swift:439)
6   FHKit                           0x0000000101867638 static FHActionManager.process<A>(actionForRecord:fromContext:) + 680 (ActionManager+Processing.swift:390)
7   FHKit                           0x0000000101866e4c static FHActionManager.process(action:forContent:fromContext:bypassingServerInteraction:withTrustedTimestamps:) + 2666060 (ActionManager+Processing.swift:26)
8   FHKit                           0x00000001019d4790 closure #1 in FHUserNotificationMessageArrivedInfo.merge(intoContext:) + 5512 (NewMessageArrived.swift:118)
9   FHKit                           0x000000010166124c thunk for @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
10  FHKit                           0x00000001016612ac thunk for @escaping @callee_guaranteed () -> () + 28 (<compiler-generated>:0)
11  CoreData                        0x00000001cc9bf834 developerSubmittedBlockToNSManagedObjectContextPerform + 156 (NSManagedObjectContext.m:3942)
12  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
13  libdispatch.dylib               0x00000001c4edc0b8 _dispatch_sync_invoke_and_complete_recurse + 64 (queue.c:1028)
14  libdispatch.dylib               0x00000001c4edbb44 _dispatch_sync_f_slow + 172 (queue.c:1785)
15  CoreData                        0x00000001cc9bfa94 -[NSManagedObjectContext performBlockAndWait:] + 264 (NSManagedObjectContext.m:4059)
16  FHKit                           0x00000001019d2ff0 FHUserNotificationMessageArrivedInfo.merge(intoContext:) + 1364 (NewMessageArrived.swift:48)
17  Fhetch                          0x0000000100547994 FHChatTableViewController.processAnyPendingNotifications() + 326036 (ChatTableViewController.swift:214)
18  Fhetch                          0x00000001005472a8 closure #1 in FHChatTableViewController.appDidBecomeActive() + 324264 (ChatTableViewController.swift:183)
19  Fhetch                          0x00000001005059ac thunk for @escaping @callee_guaranteed () -> () + 52 (<compiler-generated>:0)
20  libdispatch.dylib               0x00000001c4ecae68 _dispatch_call_block_and_release + 32 (init.c:1517)
21  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
22  libdispatch.dylib               0x00000001c4ede280 _dispatch_root_queue_drain + 680 (inline_internal.h:2622)
23  libdispatch.dylib               0x00000001c4ede96c _dispatch_worker_thread2 + 164 (queue.c:6935)
24  libsystem_pthread.dylib         0x0000000236996080 _pthread_wqthread + 228 (pthread.c:2612)
25  libsystem_pthread.dylib         0x0000000236995e5c start_wqthread + 8

Thread 11 name:
Thread 11:
0   libsystem_kernel.dylib          0x00000001fcd27bdc kevent_id + 8
1   libdispatch.dylib               0x00000001c4eef1fc _dispatch_kq_poll + 228 (event_kevent.c:750)
2   libdispatch.dylib               0x00000001c4eefc20 _dispatch_event_loop_wait_for_ownership + 444 (event_kevent.c:2209)
3   libdispatch.dylib               0x00000001c4edbf54 __DISPATCH_WAIT_FOR_QUEUE__ + 328 (queue.c:1690)
4   libdispatch.dylib               0x00000001c4edbb28 _dispatch_sync_f_slow + 144 (queue.c:1774)
5   CoreData                        0x00000001cc9bfa94 -[NSManagedObjectContext performBlockAndWait:] + 264 (NSManagedObjectContext.m:4059)
6   FHKit                           0x00000001018b1034 closure #1 in static FHAPIEndpointDescribing.execute<A>(withRequestData:responseHandler:) + 10748 (EndpointDescribing.swift:308)
7   FHKit                           0x00000001018b4324 partial apply for closure #1 in static FHAPIEndpointDescribing.execute<A>(withRequestData:responseHandler:) + 92 (<compiler-generated>:0)
8   FHKit                           0x00000001018ab054 thunk for @escaping @callee_guaranteed (@guaranteed Data?, @guaranteed NSURLResponse?, @guaranteed Error?) -> () + 268 (<compiler-generated>:0)
9   CFNetwork                       0x00000001c5a0c0bc __40-[__NSURLSessionLocal taskForClassInfo:]_block_invoke + 532 (LocalSession.mm:675)
10  CFNetwork                       0x00000001c5a1d208 __49-[__NSCFLocalSessionTask _task_onqueue_didFinish]_block_invoke_2 + 196 (LocalSessionTask.mm:543)
11  libdispatch.dylib               0x00000001c4ecae68 _dispatch_call_block_and_release + 32 (init.c:1517)
12  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
13  libdispatch.dylib               0x00000001c4ed4124 _dispatch_lane_serial_drain + 668 (inline_internal.h:2622)
14  libdispatch.dylib               0x00000001c4ed4cb4 _dispatch_lane_invoke + 444 (queue.c:3944)
15  libdispatch.dylib               0x00000001c4edf500 _dispatch_workloop_worker_thread + 648 (queue.c:6732)
16  libsystem_pthread.dylib         0x00000002369960bc _pthread_wqthread + 288 (pthread.c:2599)
17  libsystem_pthread.dylib         0x0000000236995e5c start_wqthread + 8

Thread 12:
0   libsystem_pthread.dylib         0x0000000236995e54 start_wqthread + 0

Thread 13 name:
Thread 13:
0   libsystem_kernel.dylib          0x00000001fcd28178 __ulock_wait + 8
1   libsystem_platform.dylib        0x000000023698d9ac _os_unfair_lock_lock_slow + 172 (lock.c:578)
2   FHKit                           0x00000001016ccad8 lock(_:) + 648 (ThreadAndQueueManagement.swift:144)
3   FHKit                           0x00000001016cde20 static FHThreadManager.synchronized<A>(_:shouldLogInfo:_:) + 864 (ThreadAndQueueManagement.swift:192)
4   FHKit                           0x00000001016ca460 synchronized<A>(_:shouldLogInfo:_:) + 88 (ThreadAndQueueManagement.swift:211)
5   FHKit                           0x00000001019cc8a4 static FHNetworkOperationsQueue.popNextOperation() + 124 (NetworkOperationsQueue.swift:248)
6   FHKit                           0x00000001019ccd80 closure #1 in closure #1 in static FHNetworkOperationsQueue.resume() + 88 (NetworkOperationsQueue.swift:300)
7   FHKit                           0x0000000101931048 thunk for @escaping @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
8   FHKit                           0x00000001019c330c thunk for @escaping @callee_guaranteed () -> (@out ()) + 20 (<compiler-generated>:0)
9   FHKit                           0x00000001016f3130 closure #1 in static FHKeychain.Storage.runPendingBlocks() + 64 (Keychain+Storage.swift:83)
10  FHKit                           0x0000000101840dd4 thunk for @escaping @callee_guaranteed () -> () + 52 (<compiler-generated>:0)
11  Foundation                      0x00000001c6a0aa9c __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 24 (NSOperation.m:1545)
12  Foundation                      0x00000001c6a1ce14 -[NSBlockOperation main] + 104 (NSOperation.m:1564)
13  Foundation                      0x00000001c69f51c4 __NSOPERATION_IS_INVOKING_MAIN__ + 24 (NSOperation.m:2189)
14  Foundation                      0x00000001c6a064e0 -[NSOperation start] + 788 (NSOperation.m:2206)
15  Foundation                      0x00000001c6a09ae8 __NSOPERATIONQUEUE_IS_STARTING_AN_OPERATION__ + 24 (NSOperation.m:2220)
16  Foundation                      0x00000001c6a17c90 __NSOQSchedule_f + 184 (NSOperation.m:2231)
17  libdispatch.dylib               0x00000001c4edb830 _dispatch_block_async_invoke2 + 148 (queue.c:560)
18  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
19  libdispatch.dylib               0x00000001c4ecfeec _dispatch_continuation_pop + 500 (inline_internal.h:2622)
20  libdispatch.dylib               0x00000001c4ecf558 _dispatch_async_redirect_invoke + 588 (queue.c:835)
21  libdispatch.dylib               0x00000001c4ede164 _dispatch_root_queue_drain + 396 (inline_internal.h:0)
22  libdispatch.dylib               0x00000001c4ede96c _dispatch_worker_thread2 + 164 (queue.c:6935)
23  libsystem_pthread.dylib         0x0000000236996080 _pthread_wqthread + 228 (pthread.c:2612)
24  libsystem_pthread.dylib         0x0000000236995e5c start_wqthread + 8

Thread 14 name:
Thread 14:
0   libsystem_kernel.dylib          0x00000001fcd28178 __ulock_wait + 8
1   libsystem_platform.dylib        0x000000023698d9ac _os_unfair_lock_lock_slow + 172 (lock.c:578)
2   FHKit                           0x00000001016ccad8 lock(_:) + 648 (ThreadAndQueueManagement.swift:144)
3   FHKit                           0x00000001016cde20 static FHThreadManager.synchronized<A>(_:shouldLogInfo:_:) + 864 (ThreadAndQueueManagement.swift:192)
4   FHKit                           0x00000001016ca460 synchronized<A>(_:shouldLogInfo:_:) + 88 (ThreadAndQueueManagement.swift:211)
5   FHKit                           0x00000001019cc8a4 static FHNetworkOperationsQueue.popNextOperation() + 124 (NetworkOperationsQueue.swift:248)
6   FHKit                           0x00000001019ccd80 closure #1 in closure #1 in static FHNetworkOperationsQueue.resume() + 88 (NetworkOperationsQueue.swift:300)
7   FHKit                           0x0000000101931048 thunk for @escaping @callee_guaranteed () -> () + 20 (<compiler-generated>:0)
8   FHKit                           0x00000001019c330c thunk for @escaping @callee_guaranteed () -> (@out ()) + 20 (<compiler-generated>:0)
9   FHKit                           0x00000001016f3130 closure #1 in static FHKeychain.Storage.runPendingBlocks() + 64 (Keychain+Storage.swift:83)
10  FHKit                           0x0000000101840dd4 thunk for @escaping @callee_guaranteed () -> () + 52 (<compiler-generated>:0)
11  Foundation                      0x00000001c6a0aa9c __NSBLOCKOPERATION_IS_CALLING_OUT_TO_A_BLOCK__ + 24 (NSOperation.m:1545)
12  Foundation                      0x00000001c6a1ce14 -[NSBlockOperation main] + 104 (NSOperation.m:1564)
13  Foundation                      0x00000001c69f51c4 __NSOPERATION_IS_INVOKING_MAIN__ + 24 (NSOperation.m:2189)
14  Foundation                      0x00000001c6a064e0 -[NSOperation start] + 788 (NSOperation.m:2206)
15  Foundation                      0x00000001c6a09ae8 __NSOPERATIONQUEUE_IS_STARTING_AN_OPERATION__ + 24 (NSOperation.m:2220)
16  Foundation                      0x00000001c6a17c90 __NSOQSchedule_f + 184 (NSOperation.m:2231)
17  libdispatch.dylib               0x00000001c4edb830 _dispatch_block_async_invoke2 + 148 (queue.c:560)
18  libdispatch.dylib               0x00000001c4ecca2c _dispatch_client_callout + 20 (object.m:560)
19  libdispatch.dylib               0x00000001c4ecfeec _dispatch_continuation_pop + 500 (inline_internal.h:2622)
20  libdispatch.dylib               0x00000001c4ecf558 _dispatch_async_redirect_invoke + 588 (queue.c:835)
21  libdispatch.dylib               0x00000001c4ede164 _dispatch_root_queue_drain + 396 (inline_internal.h:0)
22  libdispatch.dylib               0x00000001c4ede96c _dispatch_worker_thread2 + 164 (queue.c:6935)
23  libsystem_pthread.dylib         0x0000000236996080 _pthread_wqthread + 228 (pthread.c:2612)
24  libsystem_pthread.dylib         0x0000000236995e5c start_wqthread + 8

Thread 15:
0   libsystem_pthread.dylib         0x0000000236995e54 start_wqthread + 0


Thread 0 crashed with ARM Thread State (64-bit):
    x0: 0x0000000000000001   x1: 0x0000000000000000   x2: 0x0000000000000001   x3: 0x000000016f8ffb88
    x4: 0x0000000000000001   x5: 0x0000000000000000   x6: 0x0000000000000000   x7: 0x0000000000000403
    x8: 0x0000000000000400   x9: 0x000000021ea52580  x10: 0x0000000000000400  x11: 0x00000000000020ff
   x12: 0x0000000101014660  x13: 0x001ffe2000000000  x14: 0x0000000066400000  x15: 0x000000021ead0208
   x16: 0x0000000000000177  x17: 0xbb3000021ea51990  x18: 0x0000000000000000  x19: 0x0000000000000403
   x20: 0x0000000000000000  x21: 0x0000000000000000  x22: 0x0000000000000001  x23: 0x000000016f8ffb88
   x24: 0x0000000000000001  x25: 0x000000016f8ffb88  x26: 0x000000028080e580  x27: 0x0000000000020400
   x28: 0x000000021ea52580   fp: 0x000000016f8ffb70   lr: 0x00000001c4eef1fc
    sp: 0x000000016f8ffb10   pc: 0x00000001fcd27bdc     cpsr: 0x1000
   esr: 0x56000080  Address size fault

Can you identify which threads might be causing deadlock? maybe there is some other problem?

This is how it looks in the crashes organizer in XCode.

Any help in this regard would be much appreciated.

Thanks

Answer 1

Obviously, Thread 0 crashed because it did not get access to the queue used by a NSManagedObjectContext in line 5 with performBlockAndWait. The same queue has apparently also been used in the same thread at other lines with performBlockAndWait (10, 19, 45…). This is no problem, since performBlockAndWait can be called re-entrantly, see the docs.
However, it has apparently also been used by other threads with performBlockAndWait (Thread 9, line 15; Thread 11, line 5). It seems to me that one of these threads allocated some common resource that Thread 0 needs to complete its work - a deadlock.
It is not possible for me to find out what this critical resource is. Deadlocks are often hard to find.
A trivial suggestion that may break you code is to replace a performBlockAndWait by a performBlock and see if the affected thread continues running, even if the code is broken. Maybe this gives you some hint where to look for the problem.

Answer 2

Calling closures from notifications async fixes this. You can look at the memory graph to understand this.