1 #include <u.h>
2 #include <libc.h>
3 #include "9proc.h"
4 
5 static Lock rendlock;
6 static Uproc *rendhash[RENDHASH];
7 
8 ulong
9 rendezvous(ulong tag, ulong val)
10 {
11 	char c;
12 	ulong ret;
13 	Uproc *t, *self, **l;
14 
15 	self = _p9uproc(0);
16 	lock(&rendlock);
17 	l = &rendhash[tag%RENDHASH];
18 	for(t=*l; t; l=&t->rendhash, t=*l){
19 		if(t->rendtag==tag){
20 			*l = t->rendhash;
21 			ret = t->rendval;
22 			t->rendval = val;
23 			t->rendtag++;
24 			c = 0;
25 			unlock(&rendlock);
26 			write(t->pipe[1], &c, 1);
27 			return ret;
28 		}
29 	}
30 
31 	/* Going to sleep here. */
32 	t = self;
33 	t->rendtag = tag;
34 	t->rendval = val;
35 	t->rendhash = *l;
36 	*l = t;
37 	unlock(&rendlock);
38 	do
39 		read(t->pipe[0], &c, 1);
40 	while(t->rendtag == tag);
41 	return t->rendval;
42 }