-(void)finishCloseStore:(NS_RELEASES_ARGUMENT NSManagedObjectContext *)closingManagedObjectContext
               isSecure:(BOOL)isSecure
             onComplete:(void (^)(void))onComplete
{
    LogDebug(TAG_SECURESTORE,
            @"Broadcasting %@ notification {%@: %p, %@: %@}",
            SecureStoreWillCloseNotification,
            SecureStoreNotificationManagedObjectContextKey,
            (char *)(__bridge void *)closingManagedObjectContext, /* NOTE: printed as a pointer, DON'T call -description
                                                                     because it executes synchronously in the context's queue,
                                                                     causing all sorts of synchronization issues (like
                                                                     deadlocks). Also don't remove the cast to char *, because
                                                                     char * can't be mistakenly printed with %@, as object
                                                                     pointers, id or void * can */
            SecureStoreNotificationIsSecureKey,
            @(isSecure));

    [notificationCenter postNotificationName:SecureStoreWillCloseNotification
                                      object:self
                                    userInfo:@{SecureStoreNotificationManagedObjectContextKey: closingManagedObjectContext,
                                               SecureStoreNotificationIsSecureKey: @(isSecure)}];
    
    LogDebug(TAG_SECURESTORE, @"%@ notification broadcast", SecureStoreWillCloseNotification);

    LogInfo(TAG_SECURESTORE, @"Waiting for operations on the managed object context to complete");

    [closingManagedObjectContext performBlockAndWait:^{
        LogInfo(TAG_SECURESTORE, @"All operations on the managed object context completed");
    }];

    LogInfo(TAG_SECURESTORE, @"Releasing the last reference to the managed object context");
    closingManagedObjectContext = nil;

    [self usingAnyState:^{
        assert(state == SecureStoreClosing);

        if (state == SecureStoreClosing) {
            state = SecureStoreInitial;
            [self internalUpdateState];
            LogInfo(TAG_SECURESTORE, @"State reinitialized to %@: notifying the state change", SecureStoreStateDescription(state));
            [stateLock broadcast];
        }
        else {
            [self internalHandleBadState];
        }

        LogDebug(TAG_SECURESTORE, @"Scheduling broadcast of notification %@ on main thread", SecureStoreDidCloseNotification);

        dispatch_async(dispatch_get_main_queue(), ^{
            LogDebug(TAG_SECURESTORE, @"Broadcasting %@ notification", SecureStoreDidCloseNotification);
            [notificationCenter postNotificationName:SecureStoreDidCloseNotification object:self];
            LogDebug(TAG_SECURESTORE, @"%@ notification broadcast", SecureStoreDidCloseNotification);
        });

        LogInfo(TAG_SECURESTORE, @"Finished closing managed object context");

        if (onComplete) {
            onComplete();
        }
    }];
}

/* NOTE: printed as a pointer, DON'T call -description
because it executes synchronously in the context's queue,
causing all sorts of synchronization issues (like
deadlocks). Also don't remove the cast to char *, because
char * can't be mistakenly printed with %@, as object
pointers, id or void * can */

• if you have a managed object context with its own dedicated thread (abstracted by the framework as a queue), almost all of its methods will execute synchronously in that thread, including surprising ones like -[NSObject description], which is used to print the object to a string when using the %@ format specifier
  
• Objective C absolutely loves implicitly converting between id, void * and int, so I have to cast to something that can't be printed with %@ by mistake
  

    [closingManagedObjectContext performBlockAndWait:^{
        LogInfo(TAG_SECURESTORE, @"All operations on the managed object context completed");
    }];

hackbunny fucked around with this message at 10:35 on Mar 18, 2016