Deadlocking with a parent context

CoreDataDeadlock.m

NSManagedObjectContext *backgroundContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];

NSManagedObjectContext *mainQueueContext  = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];

mainQueueContext.parentContext = backgroundContext;

[backgroundContext performBlock:^{
    id someManagedObject = [backgroundContext objectWithID:someID];
    
    // Ensure that the object is not a fault
    someManagedObject.someProperty;

    [mainQueueContext performBlockAndWait:^{
        id mainThreadObject = [mainQueueContext objectWithID:someID];

        mainThreadObject.someProperty;
        // This will try to fulfill the fault. Since the parent context has the
        // object in its local context, it will try to pull it straight from that
        // context. BUT THAT CONTEXT IS BLOCKED in performBlockAndWait.
        //
        // DEADLOCK! To fix, use performBlock: instead of performBlockAndWait:
     }];
}];