Suspending GCD query problem

i have trouble suspending a gcd query. Here is some code that demonstrates the problem:

static dispatch_queue_t q=nil;

static void test(int a){
    if(q){
        dispatch_suspend(q);
        dispatch_release(q);
        q=nil;
    }
    q=dispatch_get_global_queue(0,0);
    dispatch_async(q,^ {
        while(1){NSLog(@"query %d",a);sleep(2);}
    });

}

int main(int argc, const char* argv[]){
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    test(1);

    //blah blah blah

    test(2);

    while(1){}
    [pool release];
    return 0;
}

What I'm trying to do is suspend,release and reinitialise query q when function test is called the second time, but apparenty my code is wrong and both instances of query q continue to run.

Your help is much appreciated, thank you.