Deadlock while using .beginAsynchronous and ListMonitor #6

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adam · 2025-12-29T15:21:53+01:00

adam commented

2025-12-29 15:21:53 +01:00

Originally created by @SteveKChiu on GitHub (Jul 23, 2015).

It seems CoreStore can result in deadlock with .beginAsynchronous and ListMonitor, from my experiment:

call CoreStote.beginAsynchronous to insert data
start CollectionView with ObjectListMonitor integration
App hang upon start

If I change CoreStote.beginAsynchronous to CoreStote.beginSynchronous, then all are fine.

I trace the problem and find out:

in CoreStote.beginAsynchronous, the last call is parentContext.saveSynchronously (NSManagedObjectContext+Transaction.swift: 96)
in ListMonitor, the last call is try! fetchedResultsController.performFetch() (ListMonitor.swift: 505)

Originally created by @SteveKChiu on GitHub (Jul 23, 2015). It seems CoreStore can result in deadlock with .beginAsynchronous and ListMonitor, from my experiment: 1. call CoreStote.beginAsynchronous to insert data 2. start CollectionView with ObjectListMonitor integration 3. App hang upon start If I change CoreStote.beginAsynchronous to CoreStote.beginSynchronous, then all are fine. I trace the problem and find out: 1. in CoreStote.beginAsynchronous, the last call is `parentContext.saveSynchronously` (NSManagedObjectContext+Transaction.swift: 96) 2. in ListMonitor, the last call is `try! fetchedResultsController.performFetch()` (ListMonitor.swift: 505)

adam added the corestore bug label 2025-12-29 15:21:53 +01:00

adam closed this issue

2025-12-29 15:21:53 +01:00

adam commented

2025-12-29 15:21:54 +01:00

@SteveKChiu commented on GitHub (Jul 23, 2015):

For develop branch, but I think it apply to main branch too.

@SteveKChiu commented on GitHub (Jul 23, 2015): For develop branch, but I think it apply to main branch too.

adam commented

2025-12-29 15:21:54 +01:00

@JohnEstropia commented on GitHub (Jul 23, 2015):

@SteveKChiu This is probably a confusion caused by having two overloads for AsynchronousDataTransaction's commit() method:

public func commit(completion: (result: SaveResult) -> Void)
public func commit()

You are probably calling the commit() method which was originally named commitAndWait(). In hindsight I should have left the name as it was to indicate blocking behavior. I'll push a fix soon.

In the mean time, you can fix this on your side with either one of two ways:

Call CoreStore.monitorList(...) before CoreStore.beginAsynchronous(...); or,
Inside the closure for beginAsynchronous(...), call transaction.commit { _ in } instead of transaction.commit()

@JohnEstropia commented on GitHub (Jul 23, 2015): @SteveKChiu This is probably a confusion caused by having two overloads for `AsynchronousDataTransaction`'s `commit()` method: ``` public func commit(completion: (result: SaveResult) -> Void) public func commit() ``` You are probably calling the `commit()` method which was originally named `commitAndWait()`. In hindsight I should have left the name as it was to indicate blocking behavior. I'll push a fix soon. In the mean time, you can fix this on your side with either one of two ways: - Call `CoreStore.monitorList(...)` before `CoreStore.beginAsynchronous(...)`; or, - Inside the closure for `beginAsynchronous(...)`, call `transaction.commit { _ in }` instead of `transaction.commit()`

adam commented

2025-12-29 15:21:54 +01:00

@SteveKChiu commented on GitHub (Jul 23, 2015):

I actually had tried the asynchronous one, but it still had the same problem. Anyway, I end up found a solution to the problem, please see my pull request. I am not sure if all modifications are necessary, but I think there is no reason to use the 'wait' version call in most case.

@SteveKChiu commented on GitHub (Jul 23, 2015): I actually had tried the asynchronous one, but it still had the same problem. Anyway, I end up found a solution to the problem, please see my pull request. I am not sure if all modifications are necessary, but I think there is no reason to use the 'wait' version call in most case.

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Reference: starred/CoreStore#6