1 8ad51794 2004-03-25 devnull #include <u.h>
 2 b2cfc4e2 2003-09-30 devnull #include <unistd.h>
 3 b2cfc4e2 2003-09-30 devnull #include <sched.h>
 4 8ad51794 2004-03-25 devnull #include <libc.h>
 5 b2cfc4e2 2003-09-30 devnull 
 6 b2cfc4e2 2003-09-30 devnull int _ntas;
 7 b2cfc4e2 2003-09-30 devnull static int
 8 b2cfc4e2 2003-09-30 devnull _xtas(void *v)
 9 b2cfc4e2 2003-09-30 devnull {
10 b2cfc4e2 2003-09-30 devnull 	int x;
11 b2cfc4e2 2003-09-30 devnull 
12 a995e477 2003-10-01 devnull 	_ntas++;
13 b2cfc4e2 2003-09-30 devnull 	x = _tas(v);
14 a995e477 2003-10-01 devnull 	return x;
15 b2cfc4e2 2003-09-30 devnull }
16 b2cfc4e2 2003-09-30 devnull 
17 b2cfc4e2 2003-09-30 devnull int
18 b2cfc4e2 2003-09-30 devnull canlock(Lock *l)
19 b2cfc4e2 2003-09-30 devnull {
20 b2cfc4e2 2003-09-30 devnull 	return !_xtas(&l->val);
21 b2cfc4e2 2003-09-30 devnull }
22 b2cfc4e2 2003-09-30 devnull 
23 b2cfc4e2 2003-09-30 devnull void
24 b2cfc4e2 2003-09-30 devnull unlock(Lock *l)
25 b2cfc4e2 2003-09-30 devnull {
26 b2cfc4e2 2003-09-30 devnull 	l->val = 0;
27 b2cfc4e2 2003-09-30 devnull }
28 b2cfc4e2 2003-09-30 devnull 
29 b2cfc4e2 2003-09-30 devnull void
30 b2cfc4e2 2003-09-30 devnull lock(Lock *lk)
31 b2cfc4e2 2003-09-30 devnull {
32 b2cfc4e2 2003-09-30 devnull 	int i;
33 b2cfc4e2 2003-09-30 devnull 
34 b2cfc4e2 2003-09-30 devnull 	/* once fast */
35 b2cfc4e2 2003-09-30 devnull 	if(!_xtas(&lk->val))
36 b2cfc4e2 2003-09-30 devnull 		return;
37 b2cfc4e2 2003-09-30 devnull 	/* a thousand times pretty fast */
38 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
39 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
40 b2cfc4e2 2003-09-30 devnull 			return;
41 b2cfc4e2 2003-09-30 devnull 		sched_yield();
42 b2cfc4e2 2003-09-30 devnull 	}
43 b2cfc4e2 2003-09-30 devnull 	/* now nice and slow */
44 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
45 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
46 b2cfc4e2 2003-09-30 devnull 			return;
47 b2cfc4e2 2003-09-30 devnull 		usleep(100*1000);
48 b2cfc4e2 2003-09-30 devnull 	}
49 b2cfc4e2 2003-09-30 devnull 	/* take your time */
50 b2cfc4e2 2003-09-30 devnull 	while(_xtas(&lk->val))
51 b2cfc4e2 2003-09-30 devnull 		usleep(1000*1000);
52 b2cfc4e2 2003-09-30 devnull }