From fc05fe1582e53e114a5fd41bd80f043e472670b8 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 2 Oct 1991 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1991-10-02

---
 pc/vga.c        |  2 +-
 port/devlance.c |  2 --
 port/portdat.h  |  4 ++--
 port/qlock.c    | 51 ++++++++++++++++++++++++++-----------------------
 4 files changed, 30 insertions(+), 29 deletions(-)

diff --git a/pc/vga.c b/pc/vga.c
index 92301d73e89d423bfb500d9583692bb90a87b8e0..fc5cab769e61e886124cd791323f268c480c9e9e 100644
--- a/pc/vga.c
+++ b/pc/vga.c
@@ -159,7 +159,7 @@ vga1(void)
 	crout(Cmode, 0xe3);	/* turn off address wrap &
 				 * word mode */
 	crout(Cmsl, 0x40);	/* 1 pixel per scan line */
-	crout(Cvertend, MAXY);	/* 480 lne display */
+	crout(Cvertend, MAXY-1);	/* 480 lne display */
 	srout(Smode, 0x06);	/* extended memory,
 				 * odd/even off */
 	srout(Sclock, 0x01);	/* 8 bits/char */
diff --git a/port/devlance.c b/port/devlance.c
index 9a48e1816eabb6ca1e3fd095f008840cfc8a6e51..b357e7a1c684f639deaa68c5fc7d61ec0b34540b 100644
--- a/port/devlance.c
+++ b/port/devlance.c
@@ -241,8 +241,6 @@ lancestclose(Queue *q)
 }
 
 /*
- *  assume the q is locked external to this routine
- *
  *  the ``connect'' control message specifyies the type
  */
 Proc *lanceout;
diff --git a/port/portdat.h b/port/portdat.h
index 9102428b6964c1a6f890e9937049d3bcd9cdfb7c..65566b1c78e3c296beff76d8def9aade0778283e 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -53,10 +53,10 @@ struct Rendez
 
 struct QLock
 {
+	Lock	use;			/* to use object */
 	Proc	*head;			/* next process waiting for object */
 	Proc	*tail;			/* last process waiting for object */
-	Lock	use;			/* to use object */
-	Lock	queue;			/* to access list */
+	int	locked;			/* flag */
 };
 
 struct Alarm
diff --git a/port/qlock.c b/port/qlock.c
index 5dceace5faba4e34496d0e28f8e68b4e1b17867c..44fdf50ed50f99585a16e38405b3fbb4f01d2638 100644
--- a/port/qlock.c
+++ b/port/qlock.c
@@ -8,34 +8,38 @@
 void
 qlock(QLock *q)
 {
-	Proc *p;
+	Proc *p, *mp;
 
-	if(canlock(&q->use))
-		return;
-	lock(&q->queue);
-	if(canlock(&q->use)){
-		unlock(&q->queue);
+	lock(&q->use);
+	if(!q->locked) {
+		q->locked = 1;
+		unlock(&q->use);
 		return;
 	}
-	if(u == 0)
-		panic("qlock");
 	p = q->tail;
+	mp = u->p;
 	if(p == 0)
-		q->head = u->p;
+		q->head = mp;
 	else
-		p->qnext = u->p;
-	q->tail = u->p;
-	u->p->qnext = 0;
-	u->p->state = Queueing;
-/*	u->p->qlock = q;	/* DEBUG */
-	unlock(&q->queue);
+		p->qnext = mp;
+	q->tail = mp;
+	mp->qnext = 0;
+	mp->state = Queueing;
+	unlock(&q->use);
 	sched();
 }
 
 int
 canqlock(QLock *q)
 {
-	return canlock(&q->use);
+	lock(&q->use);
+	if(q->locked) {
+		unlock(&q->use);
+		return 0;
+	}
+	q->locked = 1;
+	unlock(&q->use);
+	return 1;
 }
 
 void
@@ -43,17 +47,16 @@ qunlock(QLock *q)
 {
 	Proc *p;
 
-	lock(&q->queue);
-/*	u->p->qlock = 0; /* DEBUG */
-	if(q->head){
-		p = q->head;
+	lock(&q->use);
+	p = q->head;
+	if(p) {
 		q->head = p->qnext;
 		if(q->head == 0)
 			q->tail = 0;
-		unlock(&q->queue);
-		ready(p);
-	}else{
 		unlock(&q->use);
-		unlock(&q->queue);
+		ready(p);
+		return;
 	}
+	q->locked = 0;
+	unlock(&q->use);
 }