From 3138c2108f2f5bd454a718be4020574f282173e6 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Fri, 14 Mar 2003 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2003-03-14

---
 ip/iproute.c   | 23 ++++++++++++++---------
 port/portdat.h |  1 +
 port/portfns.h |  1 +
 port/proc.c    | 27 ++++++++++++++++++++++-----
 port/sysproc.c |  3 +--
 5 files changed, 39 insertions(+), 16 deletions(-)

diff --git a/ip/iproute.c b/ip/iproute.c
index 051c3a3265264b8b21853f2546f9e486a3132524..816e6685f2993fe1be722d94b2e277256bce8b1c 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -487,8 +487,9 @@ v4lookup(Fs *f, uchar *a, Conv *c)
 	Route *p, *q;
 	ulong la;
 	uchar gate[IPaddrlen];
+	Ipifc *ifc;
 
-	if(c != nil && c->r != nil && c->rgen == v4routegeneration)
+	if(c != nil && c->r != nil && c->r->ifc != nil && c->rgen == v4routegeneration)
 		return c->r;
 
 	la = nhgetl(a);
@@ -509,11 +510,13 @@ v4lookup(Fs *f, uchar *a, Conv *c)
 			memmove(gate, v4prefix, IPv4off);
 		} else
 			v4tov6(gate, q->v4.gate);
-		q->ifc = findipifc(f, gate, q->type);
-		if(q->ifc == nil)
+		ifc = findipifc(f, gate, q->type);
+		if(ifc == nil)
 			return nil;
-		q->ifcid = q->ifc->ifcid;
+		q->ifc = ifc;
+		q->ifcid = ifc->ifcid;
 	}
+
 	if(c != nil){
 		c->r = q;
 		c->rgen = v4routegeneration;
@@ -530,6 +533,7 @@ v6lookup(Fs *f, uchar *a, Conv *c)
 	int h;
 	ulong x, y;
 	uchar gate[IPaddrlen];
+	Ipifc *ifc;
 
 	if(memcmp(a, v4prefix, IPv4off) == 0){
 		q = v4lookup(f, a+IPv4off, c);
@@ -537,7 +541,7 @@ v6lookup(Fs *f, uchar *a, Conv *c)
 			return q;
 	}
 
-	if(c != nil && c->r != nil && c->rgen == v6routegeneration)
+	if(c != nil && c->r != nil && c->r->ifc != nil && c->rgen == v6routegeneration)
 		return c->r;
 
 	for(h = 0; h < IPllen; h++)
@@ -576,12 +580,13 @@ next:		;
 		if(q->type & Rifc) {
 			for(h = 0; h < IPllen; h++)
 				hnputl(gate+4*h, q->v6.address[h]);
-			q->ifc = findipifc(f, gate, q->type);
+			ifc = findipifc(f, gate, q->type);
 		} else
-			q->ifc = findipifc(f, q->v6.gate, q->type);
-		if(q->ifc == nil)
+			ifc = findipifc(f, q->v6.gate, q->type);
+		if(ifc == nil)
 			return nil;
-		q->ifcid = q->ifc->ifcid;
+		q->ifc = ifc;
+		q->ifcid = ifc->ifcid;
 	}
 	if(c != nil){
 		c->r = q;
diff --git a/port/portdat.h b/port/portdat.h
index 3d0fba91213d389c54b204e809163fca241c6380..d7da58ccd9b192a3352b6be6982f68208fe6c4c4 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -658,6 +658,7 @@ struct Proc
 	ulong	basepri;	/* base priority level */
 	uchar	fixedpri;	/* priority level deson't change */
 	int	quanta;		/* quanta left */
+	uchar	yield;		/* non-zero if the process just did a sleep(0) */
 	ulong	readytime;	/* time process came ready */
 	ulong	movetime;	/* last time process switched processors */
 	int	preempted;	/* true if this process hasn't finished the interrupt
diff --git a/port/portfns.h b/port/portfns.h
index 1d4cc1ccfe9b2b46aec268ce6520a0191f75917b..431d410ae8c2f09e384322e62e1cb1abd8d05f68 100644
--- a/port/portfns.h
+++ b/port/portfns.h
@@ -366,6 +366,7 @@ void		xinit(void);
 int		xmerge(void*, void*);
 void*		xspanalloc(ulong, int, ulong);
 void		xsummary(void);
+void		yield(void);
 Segment*	data2txt(Segment*);
 Segment*	dupseg(Segment**, int, int);
 Segment*	newseg(int, ulong, ulong);
diff --git a/port/proc.c b/port/proc.c
index 21bad1a4227e380a173571255bfa3238c9daa4e0..179c57edd81039b1bf4dfb258102e740a481ddbc 100644
--- a/port/proc.c
+++ b/port/proc.c
@@ -259,6 +259,21 @@ ready(Proc *p)
 	splx(s);
 }
 
+/*
+ *  yield the processor to any other runnable process
+ */
+void
+yield(void)
+{
+	if(anyready()){
+		up->yield = 1;
+		sched();
+	}
+}
+
+/*
+ *  pick a process to run
+ */
 Proc*
 runproc(void)
 {
@@ -282,13 +297,15 @@ loop:
 	for(i = 0;; i++){
 		/*
 		 *  find the highest priority target process that this
-		 *  processor can run given affinity constraints
+		 *  processor can run given affinity constraints.
+		 *
 		 */
 		for(rq = &runq[Nrq-1]; rq >= runq; rq--){
-			tp = rq->head;
-			if(tp == 0)
-				continue;
-			for(; tp; tp = tp->rnext){
+			for(tp = rq->head; tp; tp = tp->rnext){
+				if(tp->yield){
+					tp->yield = 0;
+					continue;
+				}	
 				if(tp->mp == nil || tp->mp == MACHP(m->machno)
 				|| (!tp->wired && i > 0))
 					goto found;
diff --git a/port/sysproc.c b/port/sysproc.c
index c23d205790aa7e547b9cd81db81a0b5887efc50c..e0eee34d70e40551ce061c51452f0e9af9a309fe 100644
--- a/port/sysproc.c
+++ b/port/sysproc.c
@@ -540,8 +540,7 @@ syssleep(ulong *arg)
 
 	n = arg[0];
 	if(n <= 0) {
-		up->priority = 0;
-		sched();
+		yield();
 		return 0;
 	}
 	if(n < TK2MS(1))