From 1b82f96703735e4ea4c23476cc484264c679cbff Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 24 Mar 1994 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1994-03-24

---
 pc/devlpt.c    | 12 ++++++------
 port/portfns.h |  2 +-
 port/proc.c    |  7 ++++++-
 port/qio.c     | 15 ++++++++++-----
 4 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/pc/devlpt.c b/pc/devlpt.c
index ae23bbb3feb2461f87becb41bcd51c8d5d7165b9..e2c2a87537e757d68ae53a4551d46319060f90a6 100644
--- a/pc/devlpt.c
+++ b/pc/devlpt.c
@@ -10,8 +10,8 @@
 
 /* base addresses */
 static int lptbase[] = {
-	0x3bc,	/* lpt1 */
-	0x378,	/* lpt2 (sic) */
+	0x378,	/* lpt1 */
+	0x3bc,	/* lpt2 */
 	0x278	/* lpt3 (sic) */
 };
 #define NDEV	(sizeof lptbase/sizeof lptbase[0])
@@ -41,7 +41,7 @@ enum
 
 static int	lptready(void*);
 static void	outch(int, int);
-static void	lptintr(Ureg*);
+static void	lptintr(Ureg*, void*);
 
 static Rendez	lptrendez;
 
@@ -89,7 +89,7 @@ lptattach(char *spec)
 
 	if(!set){
 		set = 1;
-		setvec(Parallelvec, lptintr);
+		setvec(Parallelvec, lptintr, 0);
 	}
 	if(i < 1 || i > NDEV)
 		error(Ebadarg);
@@ -217,8 +217,8 @@ lptready(void *base)
 }
 
 static void
-lptintr(Ureg *ur)
+lptintr(Ureg *ur, void *arg)
 {
-	USED(ur);
+	USED(ur, arg);
 	wakeup(&lptrendez);
 }
diff --git a/port/portfns.h b/port/portfns.h
index 9710510f31b11243eec3943f57a3a3e0bfd8a6f9..4168cc760f094ce955848d740ff60f38ef472cf0 100644
--- a/port/portfns.h
+++ b/port/portfns.h
@@ -16,7 +16,7 @@ void		buzz(int, int);
 void		cachedel(Image*, ulong);
 void		cachepage(Page*, Image*);
 void		callbacks(void);
-void		newcallback(void (*)(void));
+int		newcallback(void (*)(void));
 int		cangetc(void*);
 int		canlock(Lock*);
 int		canpage(Proc*);
diff --git a/port/proc.c b/port/proc.c
index 867fa1b07cfe111bb457949bbc991774fbb022d4..3065d7c7fb7884f7f2b2574f36f19ed8b8b6cee1 100644
--- a/port/proc.c
+++ b/port/proc.c
@@ -107,12 +107,17 @@ anyready(void)
 	return m->hiq.head != 0 || m->loq.head != 0;
 }
 
-void
+int
 newcallback(void (*func)(void))
 {
 	*m->cbin = func;
 	if(++m->cbin >= m->cbend)
 		m->cbin = m->calls;
+
+	if(m->hiq.head == 0 && m->loq.head == 0)
+		return 1;
+
+	return 0;
 }
 
 void
diff --git a/port/qio.c b/port/qio.c
index ffb7a9d688f1743982e7549b42a71f8fb6b1fbed..4a51ec131e53474b2933e5045798673a4cd90dfd 100644
--- a/port/qio.c
+++ b/port/qio.c
@@ -223,14 +223,14 @@ qpass(Queue *q, Block *b)
 		memmove(q->syncbuf, b->rp, i);
 		q->syncbuf = 0;		/* tell reader buffer is full */
 		len -= i;
-		if(len <= 0 || (q->state & Qmsg)){
+		if(len <= 0 || (q->state & Qmsg)) {
 			iunlock(q);
 			wakeup(&q->rr);
 			freeb(b);
 			return i;
 		}
-		/* queue anything that's left */
 		dowakeup = 1;
+		/* queue anything that's left */
 		b->rp += i;
 	}
 
@@ -243,6 +243,9 @@ qpass(Queue *q, Block *b)
 	q->len += len;
 checkb(b, "qpass");
 
+	if(q->len >= q->limit)
+		q->state |= Qflow;
+
 	if(q->state & Qstarve){
 		q->state &= ~Qstarve;
 		dowakeup = 1;
@@ -265,7 +268,6 @@ qproduce(Queue *q, void *vp, int len)
 	int i, dowakeup;
 	uchar *p = vp;
 
-if(debuging) print("qproduce %d\n", len);
 	/* sync with qread */
 	dowakeup = 0;
 	lock(q);
@@ -433,7 +435,7 @@ checkb(b, "qread 1");
 	q->len -= n;
 
 	/* if writer flow controlled, restart */
-	if((q->state & Qflow) && q->len < q->limit/2){
+	if((q->state & Qflow) && q->len < q->limit){
 		q->state &= ~Qflow;
 		dowakeup = 1;
 	} else
@@ -459,8 +461,11 @@ checkb(b, "qread 2");
 	}
 
 	/* wakeup flow controlled writers (with a bit of histeresis) */
-	if(dowakeup)
+	if(dowakeup){
+		if(q->kick)
+			(*q->kick)(q->arg);
 		wakeup(&q->wr);
+	}
 
 	poperror();
 	qunlock(&q->rlock);