dispatch_semaphore test?

gistfile1.m

#import <Foundation/Foundation.h>
#import <dispatch/dispatch.h>

int main (int argc, char const *argv[])
{
    int i;
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(1);
    
    for(i = 0; i < 10; i++) {
        dispatch_async(queue, ^{
            NSLog(@"signal %d %@", i, [NSThread currentThread]);
            dispatch_semaphore_signal(semaphore);
        });
    }
    
    dispatch_async(queue, ^{
        NSLog(@"wait %@", [NSThread currentThread]);
        int j = 0;
        while(1) {
            dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
            NSLog(@"count: %d", j);
            sleep(1);
            j++;
        }
    });
    
    dispatch_main();
    
    return 0;
}