使用AFIncrementalStore和NSFetchedResultsController进行死锁 [英] Deadlock using AFIncrementalStore and NSFetchedResultsController

问题描述

我一直在打击我的头几天现在，不能为我的生活弄清楚发生了什么。我对核心数据很绿，但我知道它足够好，以避免死锁情况。然而对于这个项目，我决定尝试并纳入AFIncrementalStore。我构建了一个示例项目来测试APIClient，以便正确映射键/值，而不会影响我的实际项目。它工作正常。

I've been bashing my head against this for a few days now and cannot for the life of me figure out what is going on. I'm pretty green with Core Data, but I know it well enough to avoid deadlock scenarios. However for this project I decided to try and incorporate AFIncrementalStore. I built a sample project to test the APIClient in order to map keys/values appropriately without messing with my actual project. It worked flawlessly.

现在我在我的实际项目中使用它，而且事情很麻烦。 NSFetchedResultsController在UITableViewController中使用，它被推离屏幕（在类似于Facebook应用的菜单中滑动）。大约50％的时间我没有得到一个死锁。我确保NSFetchedResultsController managedObjectContext与我的AppDelegate相同。几乎所有的设置都与AFIncrementalStore示例相同。即使我的示例项目测试用法完美。

Now I'm using it in my actual project and things are finicky. The NSFetchedResultsController is used in a UITableViewController that gets pushed off screen (slide in menu similar to Facebook app). About 50% of the time I don't get a deadlock. I've made sure that the NSFetchedResultsController managedObjectContext is the same as my AppDelegate. Nearly everything is setup identical to the AFIncrementalStore examples. Even my sample project to test out the usage works perfectly.

这是Debug Navigator在死锁期间暂停时的图片。看起来问题在于AFIncrementalStore的后台上下文和主线程的上下文。但是我不知道该怎么做，因为我没有写入AFIncrementalStore，只是去掉现有的文档/示例。

Here is an image of the Debug Navigator when I pause during the deadlock. It looks like the problem lies between AFIncrementalStore's background context and the main thread's context. However I'm not sure what to do since I didn't write AFIncrementalStore and am just going off of the existing docs/examples.

编辑：添加第二个线程的回溯

edit: Adding the backtrace of the 2nd thread

thread #2: tid = 0x2103, 0x925d180e libsystem_kernel.dylib`semaphore_wait_trap + 10
frame #0: 0x925d180e libsystem_kernel.dylib`semaphore_wait_trap + 10
frame #1: 0x0258cf08 libdispatch.dylib`_dispatch_thread_semaphore_wait + 16
frame #2: 0x0258ab3a libdispatch.dylib`_dispatch_barrier_sync_f_slow + 149
frame #3: 0x0258aa5c libdispatch.dylib`dispatch_barrier_sync_f + 37
frame #4: 0x00b64c8b CoreData`_perform + 187
frame #5: 0x00b67659 CoreData`-[NSManagedObjectContext(_NestedContextSupport) managedObjectContextDidUnregisterObjectsWithIDs:] + 73
frame #6: 0x00bdf2db CoreData`__97-[NSManagedObjectContext(_NestedContextSupport) managedObjectContextDidUnregisterObjectsWithIDs:]_block_invoke_0 + 75
frame #7: 0x00b64cc1 CoreData`internalBlockToNSManagedObjectContextPerform + 17
frame #8: 0x0259b014 libdispatch.dylib`_dispatch_client_callout + 14
frame #9: 0x0258ad5f libdispatch.dylib`_dispatch_barrier_sync_f_invoke + 58
frame #10: 0x0258aaa3 libdispatch.dylib`dispatch_barrier_sync_f + 108
frame #11: 0x00b64c8b CoreData`_perform + 187
frame #12: 0x00b67659 CoreData`-[NSManagedObjectContext(_NestedContextSupport) managedObjectContextDidUnregisterObjectsWithIDs:] + 73
frame #13: 0x00b71c8c CoreData`-[NSManagedObjectContext(_NSInternalAdditions) _disposeObjects:count:notifyParent:] + 444
frame #14: 0x00b71305 CoreData`-[NSManagedObjectContext(_NSInternalAdditions) _dispose:] + 597
frame #15: 0x00b70e15 CoreData`-[NSManagedObjectContext _dealloc__] + 325
frame #16: 0x00bd872f CoreData`internalBlockToDeallocNSManagedObjectContext + 79
frame #17: 0x0259b014 libdispatch.dylib`_dispatch_client_callout + 14
frame #18: 0x0258b418 libdispatch.dylib`_dispatch_queue_drain + 239
frame #19: 0x0258b2a6 libdispatch.dylib`_dispatch_queue_invoke + 59
frame #20: 0x0258c280 libdispatch.dylib`_dispatch_root_queue_drain + 231
frame #21: 0x0258c450 libdispatch.dylib`_dispatch_worker_thread2 + 39
frame #22: 0x971cde12 libsystem_c.dylib`_pthread_wqthread + 441

推荐答案

我不是任何方式的CoreData专家，所以用一粒盐。

I'm not a CoreData expert by any means, so take this with a grain of salt.

看来，可能，你正在使用NSPrivateQueueConcurrencyType。看起来AFIncrementalStore正在使用主队列进行同步。这是在你的控制下吗？

It looks like, possibly, you are using the NSPrivateQueueConcurrencyType. It appears that AFIncrementalStore is using the main queue for synchronization. Is that under your control?

您可以尝试将NSManagedObjectContext切换到NSMainQueueConcurrencyType，看看是否有帮助？

Can you try switching your NSManagedObjectContext to NSMainQueueConcurrencyType and see if that helps?

你正在使用NSPrivateQueueConcurrencyType，你可能是为了性能的原因。所以，这可能不是一个伟大的长期解决方案...

Now, if I'm right and you are using NSPrivateQueueConcurrencyType, you're probably doing it for a performance reason. So, this might not be a great long-term solution...

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