From 611464ba166de69d4145cff82353909d5f120019 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Sat, 11 May 1996 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1996-05-11

---
 carrera/dat.h  |  1 +
 pc/dat.h       |  1 +
 port/portdat.h |  1 +
 port/proc.c    |  8 ++++++--
 port/taslock.c | 54 ++++++++++++++++++++++++++++++++------------------
 power/dat.h    |  1 +
 6 files changed, 45 insertions(+), 21 deletions(-)

diff --git a/carrera/dat.h b/carrera/dat.h
index e4dffff10d14c50ece09aaf70e20da9462bb8885..d285b53735cdaa3ecec03b63f9d5d4e1479d7b2e 100644
--- a/carrera/dat.h
+++ b/carrera/dat.h
@@ -27,6 +27,7 @@ struct Lock
 	ulong	sr;
 	ulong	pc;
 	ulong	pid;
+	int	pri;
 };
 
 struct Label
diff --git a/pc/dat.h b/pc/dat.h
index 9d978318a6cf857cebd489e6b743b1f40ca756bc..22795973d5a0171b66ec0b108177a9a8bbd97fec 100644
--- a/pc/dat.h
+++ b/pc/dat.h
@@ -30,6 +30,7 @@ struct Lock
 	ulong	sr;
 	ulong	pc;
 	ulong	pid;
+	int	pri;
 };
 
 struct Label
diff --git a/port/portdat.h b/port/portdat.h
index ef34aa59cca951b65a26f91affd19ea9907fe407..47dd3941ded2049f400d3db426da4f86c9dcc8c7 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -507,6 +507,7 @@ enum
 	NNOTE = 5,
 
 	Nrq		= 20,	/* number of scheduler priority levels */
+	PriLock		= 19,	/* priority for processes holding locks */
 	PriNormal	= 10,	/* base priority for normal processes */
 	PriKproc	= 13,	/* base priority for kernel processes */
 	PriRoot		= 13,	/* base priority for root processes */
diff --git a/port/proc.c b/port/proc.c
index fc9ebbfa788d442fc887d29bed7e03f859d644c6..3686fbbcedc99199b263a17fd13bf31256d11c56 100644
--- a/port/proc.c
+++ b/port/proc.c
@@ -137,8 +137,12 @@ ready(Proc *p)
 
 	/* history counts */
 	if(p->state == Running){
-		p->rt++;
-		pri = ((p->art + (p->rt<<1))>>2)/Squantum;
+		if(up->priority == PriLock){
+			pri = 0;
+		} else {
+			p->rt++;
+			pri = ((p->art + (p->rt<<1))>>2)/Squantum;
+		}
 	} else {
 		p->art = (p->art + (p->rt<<1))>>2;
 		p->rt = 0;
diff --git a/port/taslock.c b/port/taslock.c
index f0b2598273fca18fb949c62cf115fa737af456e7..bf1e5f07e21fd7db6953af66446425c64da4571d 100644
--- a/port/taslock.c
+++ b/port/taslock.c
@@ -16,31 +16,34 @@ lockloop(Lock *l, ulong pc)
 void
 lock(Lock *l)
 {
-	int i;
-	ulong pc, pid;
+	int pri, i;
+	ulong pc;
 
 	pc = getcallerpc(l);
-	pid = up ? up->pid : 0;
 
-	if(tas(&l->key) == 0){
-		l->pc = pc;
-		l->pid = pid;
+	if(up == 0) {
+		for(i=0; i<1000000; i++)
+			if(tas(&l->key) == 0){
+				l->pc = pc;
+				return;
+			}
+		lockloop(l, pc);
 		return;
 	}
 
-	for(;;){
-		i = 0;
-		while(l->key)
-			if(i++ > 100000000){
-				i = 0;
-				lockloop(l, pc);
-			}
+	pri = up->priority;
+	up->priority = PriLock;
+
+	for(i=0; i<1000; i++){
 		if(tas(&l->key) == 0){
+			l->pri = pri;
 			l->pc = pc;
-			l->pid = pid;
 			return;
 		}
+		if(conf.nmach == 1 && up->state == Running && (getstatus()&IE))
+			sched();
 	}
+	lockloop(l, pc);
 }
 
 void
@@ -75,19 +78,32 @@ ilock(Lock *l)
 int
 canlock(Lock *l)
 {
-	if(tas(&l->key))
-		return 0;
+	int pri;
 
-	l->pc = getcallerpc(l);
-	l->pid = up ? up->pid : 0;
+	SET(pri);
+	if(up) {
+		pri = up->priority;
+		up->priority = PriLock;
+	}
+	if(tas(&l->key)) {
+		up->priority = pri;
+		l->pc = getcallerpc(l);
+		return 0;
+	}
+	l->pri = pri;
 	return 1;
 }
 
 void
 unlock(Lock *l)
 {
-	l->key = 0;
+	int p;
+
+	p = l->pri;
 	l->pc = 0;
+	l->key = 0;
+	if(up != 0)
+		up->priority = p;
 }
 
 void
diff --git a/power/dat.h b/power/dat.h
index 1f00ead903a08150e38a5d8012e9b49a58708cc5..b70b42b8a673b8a71e9179beeebe5eb086c04905 100644
--- a/power/dat.h
+++ b/power/dat.h
@@ -26,6 +26,7 @@ struct Lock
 	ulong	pc;
 	ulong	sr;
 	ulong	pid;
+	int	pri;
 };
 
 struct Label