dispatch_syncに絶望してこんな事をしている

gistfile1.m

    __block dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    dispatch_async(queue, ^{
        // hogehoge
        // ここに処理を書く
        //
        dispatch_semaphore_signal(semaphore);
    });
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    dispatch_release(semaphore);