1 8ad51794 2004-03-25 devnull #include <u.h>
 2 b2cfc4e2 2003-09-30 devnull #include <unistd.h>
 3 a16e9f2d 2004-04-20 devnull #include <sys/time.h>
 4 b2cfc4e2 2003-09-30 devnull #include <sched.h>
 5 8ad51794 2004-03-25 devnull #include <libc.h>
 6 b2cfc4e2 2003-09-30 devnull 
 7 b2cfc4e2 2003-09-30 devnull int _ntas;
 8 b2cfc4e2 2003-09-30 devnull static int
 9 b2cfc4e2 2003-09-30 devnull _xtas(void *v)
10 b2cfc4e2 2003-09-30 devnull {
11 b2cfc4e2 2003-09-30 devnull 	int x;
12 b2cfc4e2 2003-09-30 devnull 
13 a995e477 2003-10-01 devnull 	_ntas++;
14 b2cfc4e2 2003-09-30 devnull 	x = _tas(v);
15 a995e477 2003-10-01 devnull 	return x;
16 b2cfc4e2 2003-09-30 devnull }
17 b2cfc4e2 2003-09-30 devnull 
18 b2cfc4e2 2003-09-30 devnull int
19 b2cfc4e2 2003-09-30 devnull canlock(Lock *l)
20 b2cfc4e2 2003-09-30 devnull {
21 b2cfc4e2 2003-09-30 devnull 	return !_xtas(&l->val);
22 b2cfc4e2 2003-09-30 devnull }
23 b2cfc4e2 2003-09-30 devnull 
24 b2cfc4e2 2003-09-30 devnull void
25 b2cfc4e2 2003-09-30 devnull unlock(Lock *l)
26 b2cfc4e2 2003-09-30 devnull {
27 b2cfc4e2 2003-09-30 devnull 	l->val = 0;
28 b2cfc4e2 2003-09-30 devnull }
29 b2cfc4e2 2003-09-30 devnull 
30 b2cfc4e2 2003-09-30 devnull void
31 b2cfc4e2 2003-09-30 devnull lock(Lock *lk)
32 b2cfc4e2 2003-09-30 devnull {
33 b2cfc4e2 2003-09-30 devnull 	int i;
34 b2cfc4e2 2003-09-30 devnull 
35 b2cfc4e2 2003-09-30 devnull 	/* once fast */
36 b2cfc4e2 2003-09-30 devnull 	if(!_xtas(&lk->val))
37 b2cfc4e2 2003-09-30 devnull 		return;
38 b2cfc4e2 2003-09-30 devnull 	/* a thousand times pretty fast */
39 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
40 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
41 b2cfc4e2 2003-09-30 devnull 			return;
42 b2cfc4e2 2003-09-30 devnull 		sched_yield();
43 b2cfc4e2 2003-09-30 devnull 	}
44 b2cfc4e2 2003-09-30 devnull 	/* now nice and slow */
45 b2cfc4e2 2003-09-30 devnull 	for(i=0; i<1000; i++){
46 b2cfc4e2 2003-09-30 devnull 		if(!_xtas(&lk->val))
47 b2cfc4e2 2003-09-30 devnull 			return;
48 b2cfc4e2 2003-09-30 devnull 		usleep(100*1000);
49 b2cfc4e2 2003-09-30 devnull 	}
50 b2cfc4e2 2003-09-30 devnull 	/* take your time */
51 b2cfc4e2 2003-09-30 devnull 	while(_xtas(&lk->val))
52 b2cfc4e2 2003-09-30 devnull 		usleep(1000*1000);
53 b2cfc4e2 2003-09-30 devnull }