Various additions and fixes.

src/lib9/rendez.c

@@ -0,0 +1,42 @@
+#include <u.h>
+#include <libc.h>
+#include "9proc.h"
+
+static Lock rendlock;
+static Uproc *rendhash[RENDHASH];
+
+ulong
+rendezvous(ulong tag, ulong val)
+{
+	char c;
+	ulong ret;
+	Uproc *t, *self, **l;
+
+	self = _p9uproc();
+	lock(&rendlock);
+	l = &rendhash[tag%RENDHASH];
+	for(t=*l; t; l=&t->rendhash, t=*l){
+		if(t->rendtag==tag){
+			*l = t->rendhash;
+			ret = t->rendval;
+			t->rendval = val;
+			t->rendtag++;
+			c = 0;
+			unlock(&rendlock);
+			write(t->pipe[1], &c, 1);
+			return ret;
+		}
+	}
+
+	/* Going to sleep here. */
+	t = self;
+	t->rendtag = tag;
+	t->rendval = val;
+	t->rendhash = *l;
+	*l = t;
+	unlock(&rendlock);
+	do
+		read(t->pipe[0], &c, 1);
+	while(t->rendtag == tag);
+	return t->rendval;
+}