1 b2cfc4e2 2003-09-30 devnull #include <unistd.h>
 2 b2cfc4e2 2003-09-30 devnull #include <sched.h>
 3 b2cfc4e2 2003-09-30 devnull #include <lib9.h>
 4 b2cfc4e2 2003-09-30 devnull 
 5 b2cfc4e2 2003-09-30 devnull int _ntas;
 6 b2cfc4e2 2003-09-30 devnull static int
 7 b2cfc4e2 2003-09-30 devnull _xtas(void *v)
 8 b2cfc4e2 2003-09-30 devnull {
 9 b2cfc4e2 2003-09-30 devnull 	int x;
10 b2cfc4e2 2003-09-30 devnull 
11 b2cfc4e2 2003-09-30 devnull _ntas++;
12 b2cfc4e2 2003-09-30 devnull 	x = _tas(v);
13 b2cfc4e2 2003-09-30 devnull 	if(x == 0 || x == 0xCAFEBABE)
14 b2cfc4e2 2003-09-30 devnull 		return x;
15 b2cfc4e2 2003-09-30 devnull 	fprint(2, "%d: tas %p got %ux\n", getpid(), v, x);
16 b2cfc4e2 2003-09-30 devnull 	abort();
17 b2cfc4e2 2003-09-30 devnull }
18 b2cfc4e2 2003-09-30 devnull 
19 b2cfc4e2 2003-09-30 devnull int
20 b2cfc4e2 2003-09-30 devnull canlock(Lock *l)
21 b2cfc4e2 2003-09-30 devnull {
22 b2cfc4e2 2003-09-30 devnull 	return !_xtas(&l->val);
23 b2cfc4e2 2003-09-30 devnull }
24 b2cfc4e2 2003-09-30 devnull 
25 b2cfc4e2 2003-09-30 devnull void
26 b2cfc4e2 2003-09-30 devnull unlock(Lock *l)
27 b2cfc4e2 2003-09-30 devnull {
28 b2cfc4e2 2003-09-30 devnull 	l->val = 0;
29 b2cfc4e2 2003-09-30 devnull }
30 b2cfc4e2 2003-09-30 devnull 
31 b2cfc4e2 2003-09-30 devnull void
32 b2cfc4e2 2003-09-30 devnull lock(Lock *lk)
33 b2cfc4e2 2003-09-30 devnull {
34 b2cfc4e2 2003-09-30 devnull 	int i;
35 b2cfc4e2 2003-09-30 devnull 
36 b2cfc4e2 2003-09-30 devnull 	/* once fast */
37 b2cfc4e2 2003-09-30 devnull 	if(!_xtas(&lk->val))
38 b2cfc4e2 2003-09-30 devnull 		return;
39 b2cfc4e2 2003-09-30 devnull 	/* a thousand times pretty fast */
40 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
41 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
42 b2cfc4e2 2003-09-30 devnull 			return;
43 b2cfc4e2 2003-09-30 devnull 		sched_yield();
44 b2cfc4e2 2003-09-30 devnull 	}
45 b2cfc4e2 2003-09-30 devnull 	/* now nice and slow */
46 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
47 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
48 b2cfc4e2 2003-09-30 devnull 			return;
49 b2cfc4e2 2003-09-30 devnull 		usleep(100*1000);
50 b2cfc4e2 2003-09-30 devnull 	}
51 b2cfc4e2 2003-09-30 devnull 	/* take your time */
52 b2cfc4e2 2003-09-30 devnull 	while(_xtas(&lk->val))
53 b2cfc4e2 2003-09-30 devnull 		usleep(1000*1000);
54 b2cfc4e2 2003-09-30 devnull }