RaceCondition using GCD in Objective-C

RaceCondition in Coding Test

/*
 RaceCondition using GCD in Objective-C
 localCountLabel and globalCountLabel increment 1, 5 through each Thread
*/

__block NSUInteger localCount1, localCount2, localCount3, globalCount;
UILabel *localCountLabel1, *localCountLabel2, *localCountLabel3, *globalCountLabel;

localCountLabel1 = [[UILabel alloc]init];
localCountLabel2 = [[UILabel alloc]init];
localCountLabel3 = [[UILabel alloc]init];
globalCountLabel = [[UILabel alloc]init];

localCount1 = localCount2 = localCount3 = globalCount = 0;

localCountLabel1.text = localCountLabel2.text = localCountLabel3.text = globalCountLabel.text = @"0";

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    while (true) {
        localCount1++;
        globalCount += 5;
        NSLog(@"LocalCount1 Thread : %d %d", localCount1, globalCount);
        dispatch_async(dispatch_get_main_queue(), ^{
            localCountLabel1.text = [NSString stringWithFormat:@"localCount1 : %d", localCount1];
            globalCountLabel.text = [NSString stringWithFormat:@"globalCount : %d", globalCount];
        });
    }
});

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    while (true) {
        localCount2++;
        globalCount += 5;
        NSLog(@"LocalCount2 Thread : %d %d", localCount2, globalCount);
        dispatch_async(dispatch_get_main_queue(), ^{
            localCountLabel2.text = [NSString stringWithFormat:@"localCount2 : %d", localCount2];
            globalCountLabel.text = [NSString stringWithFormat:@"globalCount : %d", globalCount];
        });
    }
});

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    while (true) {
        localCount3++;
        globalCount += 5;
        NSLog(@"LocalCount3 Thread : %d %d", localCount3, globalCount);
        dispatch_async(dispatch_get_main_queue(), ^{
            localCountLabel3.text = [NSString stringWithFormat:@"localCount3 : %d", localCount3];
            globalCountLabel.text = [NSString stringWithFormat:@"globalCount : %d", globalCount];
        });
    }
});