add wait

src/libthread/wait.c

@@ -0,0 +1,93 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+
+typedef struct Waiter Waiter;
+
+struct {
+	QLock lk;
+	Waitmsg **msg;
+	int nmsg;
+	int muxer;
+	Waiter *head;
+} waiting;
+
+struct Waiter
+{
+	Rendez r;
+	Waitmsg *msg;
+	int pid;
+	Waiter *next;
+	Waiter *prev;
+};
+
+/* see src/libmux/mux.c */
+Waitmsg*
+procwait(int pid)
+{
+	Waiter *w;
+	Waiter me;
+	Waitmsg *msg;
+	int i;
+	
+	memset(&me, 0, sizeof me);
+	me.pid = pid;
+	me.r.l = &waiting.lk;
+	
+	qlock(&waiting.lk);
+	for(i=0; i<waiting.nmsg; i++){
+		if(waiting.msg[i]->pid == pid){
+			msg = waiting.msg[i];
+			waiting.msg[i] = waiting.msg[--waiting.nmsg];
+			qunlock(&waiting.lk);
+			return msg;
+		}
+	}
+	me.next = waiting.head;
+	me.prev = nil;
+	if(me.next)
+		me.next->prev = &me;
+	waiting.head = &me;
+	while(waiting.muxer && me.msg==nil)
+		rsleep(&me.r);
+
+	if(!me.msg){
+		if(waiting.muxer)
+			abort();
+		waiting.muxer = 1;
+		while(!me.msg){
+			qunlock(&waiting.lk);
+			msg = recvp(threadwaitchan());
+			qlock(&waiting.lk);
+			if(msg == nil)	/* shouldn't happen */
+				break;
+			for(w=waiting.head; w; w=w->next)
+				if(w->pid == msg->pid)
+					break;
+			if(w){
+				if(w->prev)
+					w->prev->next = w->next;
+				else
+					waiting.head = w->next;
+				if(w->next)
+					w->next->prev = w->prev;
+				me.msg = msg;
+				rwakeup(&w->r);
+			}else{
+				waiting.msg = realloc(waiting.msg, (waiting.nmsg+1)*sizeof waiting.msg[0]);
+				if(waiting.msg == nil)
+					sysfatal("out of memory");
+				waiting.msg[waiting.nmsg++] = msg;
+			}
+		}
+		waiting.muxer = 0;
+		if(waiting.head)
+			rwakeup(&waiting.head->r);
+	}
+	qunlock(&waiting.lk);
+	if (me.msg->pid < 0) {
+		free(me.msg);
+		me.msg = 0;
+	}
+	return me.msg;
+}