In non-blocking recv functions in libmux and libdraw,

distinguish between "cannot receive without blocking"
and "EOF on connection".

In libmux, do not elect async guys muxers, so that
synchronous RPC calls run in the main event loop
(e.g., in eresized) do not get stuck.

Fixes problem reported by Lu Xuxiao, namely that
jpg etc. would spin at 100% cpu usage.

3 files changed, 50 insertions, 41 deletions

diff --git a/src/libmux/io.c b/src/libmux/io.c
index 4a89ca22..d9d9d8a6 100644
--- a/src/libmux/io.c
+++ b/src/libmux/io.c
@@ -34,7 +34,7 @@ _muxrecvproc(void *v)
 	qunlock(&mux->inlk);
 	qlock(&mux->lk);
 	_muxqhangup(q);
-	while((p = _muxnbqrecv(q)) != nil)
+	while(_muxnbqrecv(q, &p))
 		free(p);
 	free(q);
 	mux->readq = nil;
@@ -64,7 +64,7 @@ _muxsendproc(void *v)
 	qunlock(&mux->outlk);
 	qlock(&mux->lk);
 	_muxqhangup(q);
-	while((p = _muxnbqrecv(q)) != nil)
+	while(_muxnbqrecv(q, &p))
 		free(p);
 	free(q);
 	mux->writeq = nil;
@@ -73,42 +73,39 @@ _muxsendproc(void *v)
 	return;
 }
 
-void*
-_muxrecv(Mux *mux, int canblock)
+int
+_muxrecv(Mux *mux, int canblock, void **vp)
 {
 	void *p;
+	int ret;
 
 	qlock(&mux->lk);
-/*
-	if(mux->state != VtStateConnected){
-		werrstr("not connected");
-		qunlock(&mux->lk);
-		return nil;
-	}
-*/
 	if(mux->readq){
 		qunlock(&mux->lk);
-		if(canblock)
-			return _muxqrecv(mux->readq);
-		return _muxnbqrecv(mux->readq);
+		if(canblock){
+			*vp = _muxqrecv(mux->readq);
+			return 1;
+		}
+		return _muxnbqrecv(mux->readq, vp);
 	}
 
 	qlock(&mux->inlk);
 	qunlock(&mux->lk);
-	if(canblock)
+	if(canblock){
 		p = mux->recv(mux);
-	else{
+		ret = 1;
+	}else{
 		if(mux->nbrecv)
-			p = mux->nbrecv(mux);
-		else
+			ret = mux->nbrecv(mux, &p);
+		else{
+			/* send eof, not "no packet ready" */
 			p = nil;
+			ret = 1;
+		}
 	}
 	qunlock(&mux->inlk);
-/*
-	if(!p && canblock)
-		vthangup(mux);
-*/
-	return p;
+	*vp = p;
+	return ret;
 }
 
 int
diff --git a/src/libmux/mux.c b/src/libmux/mux.c
index bfabb238..8257fb0e 100644
--- a/src/libmux/mux.c
+++ b/src/libmux/mux.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2003 Russ Cox, Massachusetts Institute of Technology */
+/* Copyright (C) 2003-2006 Russ Cox, Massachusetts Institute of Technology */
 /* See COPYRIGHT */
 
 /*
@@ -100,12 +100,17 @@ muxmsgandqlock(Mux *mux, void *p)
 void
 electmuxer(Mux *mux)
 {
+	Muxrpc *rpc;
+
 	/* if there is anyone else sleeping, wake them to mux */
-	if(mux->sleep.next != &mux->sleep){
-		mux->muxer = mux->sleep.next;
-		rwakeup(&mux->muxer->r);
-	}else
-		mux->muxer = nil;
+	for(rpc=mux->sleep.next; rpc != &mux->sleep; rpc = rpc->next){
+		if(!rpc->async){
+			mux->muxer = rpc;
+			rwakeup(&rpc->r);
+			return;
+		}
+	}
+	mux->muxer = nil;
 }
 
 void*
@@ -133,7 +138,7 @@ muxrpc(Mux *mux, void *tx)
 		mux->muxer = r;
 		while(!r->p){
 			qunlock(&mux->lk);
-			p = _muxrecv(mux, 1);
+			_muxrecv(mux, 1, &p);
 			if(p == nil){
 				/* eof -- just give up and pass the buck */
 				qlock(&mux->lk);
@@ -144,7 +149,6 @@ muxrpc(Mux *mux, void *tx)
 		}
 		electmuxer(mux);
 	}
-/*print("finished %p\n", r); */
 	p = r->p;
 	puttag(mux, r);
 	qunlock(&mux->lk);
@@ -161,24 +165,29 @@ muxrpcstart(Mux *mux, void *tx)
 
 	if((r = allocmuxrpc(mux)) == nil)
 		return nil;
+	r->async = 1;
 	if((tag = tagmuxrpc(r, tx)) < 0)
 		return nil;
 	return r;
 }
 
-void*
-muxrpccanfinish(Muxrpc *r)
+int
+muxrpccanfinish(Muxrpc *r, void **vp)
 {
-	char *p;
+	void *p;
 	Mux *mux;
-	
+	int ret;
+
 	mux = r->mux;
 	qlock(&mux->lk);
+	ret = 1;
 	if(!r->p && !mux->muxer){
 		mux->muxer = r;
 		while(!r->p){
 			qunlock(&mux->lk);
-			p = _muxrecv(mux, 0);
+			p = nil;
+			if(!_muxrecv(mux, 0, &p))
+				ret = 0;
 			if(p == nil){
 				qlock(&mux->lk);
 				break;
@@ -191,7 +200,8 @@ muxrpccanfinish(Muxrpc *r)
 	if(p)
 		puttag(mux, r);
 	qunlock(&mux->lk);
-	return p;
+	*vp = p;
+	return ret;
 }
 
 static void
diff --git a/src/libmux/queue.c b/src/libmux/queue.c
index 1cadbe6c..2151c252 100644
--- a/src/libmux/queue.c
+++ b/src/libmux/queue.c
@@ -81,8 +81,8 @@ _muxqrecv(Muxqueue *q)
 	return p;
 }
 
-void*
-_muxnbqrecv(Muxqueue *q)
+int
+_muxnbqrecv(Muxqueue *q, void **vp)
 {
 	void *p;
 	Qel *e;
@@ -90,14 +90,16 @@ _muxnbqrecv(Muxqueue *q)
 	qlock(&q->lk);
 	if(q->head == nil){
 		qunlock(&q->lk);
-		return nil;
+		*vp = nil;
+		return q->hungup;
 	}
 	e = q->head;
 	q->head = e->next;
 	qunlock(&q->lk);
 	p = e->p;
 	free(e);
-	return p;
+	*vp = p;
+	return 1;
 }
 
 void