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 a995e477 2003-10-01 devnull 	_ntas++;
12 b2cfc4e2 2003-09-30 devnull 	x = _tas(v);
13 a995e477 2003-10-01 devnull 	return x;
14 b2cfc4e2 2003-09-30 devnull }
15 b2cfc4e2 2003-09-30 devnull 
16 b2cfc4e2 2003-09-30 devnull int
17 b2cfc4e2 2003-09-30 devnull canlock(Lock *l)
18 b2cfc4e2 2003-09-30 devnull {
19 b2cfc4e2 2003-09-30 devnull 	return !_xtas(&l->val);
20 b2cfc4e2 2003-09-30 devnull }
21 b2cfc4e2 2003-09-30 devnull 
22 b2cfc4e2 2003-09-30 devnull void
23 b2cfc4e2 2003-09-30 devnull unlock(Lock *l)
24 b2cfc4e2 2003-09-30 devnull {
25 b2cfc4e2 2003-09-30 devnull 	l->val = 0;
26 b2cfc4e2 2003-09-30 devnull }
27 b2cfc4e2 2003-09-30 devnull 
28 b2cfc4e2 2003-09-30 devnull void
29 b2cfc4e2 2003-09-30 devnull lock(Lock *lk)
30 b2cfc4e2 2003-09-30 devnull {
31 b2cfc4e2 2003-09-30 devnull 	int i;
32 b2cfc4e2 2003-09-30 devnull 
33 b2cfc4e2 2003-09-30 devnull 	/* once fast */
34 b2cfc4e2 2003-09-30 devnull 	if(!_xtas(&lk->val))
35 b2cfc4e2 2003-09-30 devnull 		return;
36 b2cfc4e2 2003-09-30 devnull 	/* a thousand times pretty fast */
37 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
38 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
39 b2cfc4e2 2003-09-30 devnull 			return;
40 b2cfc4e2 2003-09-30 devnull 		sched_yield();
41 b2cfc4e2 2003-09-30 devnull 	}
42 b2cfc4e2 2003-09-30 devnull 	/* now nice and slow */
43 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
44 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
45 b2cfc4e2 2003-09-30 devnull 			return;
46 b2cfc4e2 2003-09-30 devnull 		usleep(100*1000);
47 b2cfc4e2 2003-09-30 devnull 	}
48 b2cfc4e2 2003-09-30 devnull 	/* take your time */
49 b2cfc4e2 2003-09-30 devnull 	while(_xtas(&lk->val))
50 b2cfc4e2 2003-09-30 devnull 		usleep(1000*1000);
51 b2cfc4e2 2003-09-30 devnull }