From b2d380ccbed1a4781e7a8069d6197ba417bdc1c1 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Sat, 16 May 1998 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1998-05-16

---
 ip/ipifc.c     |  17 ++++++--
 pc/devata.c    | 111 +++++++++++++++++++++----------------------------
 pc/trap.c      |  25 ++++++-----
 port/portdat.h |   3 ++
 4 files changed, 75 insertions(+), 81 deletions(-)

diff --git a/ip/ipifc.c b/ip/ipifc.c
index ae724e2146785739b897093df314684be04baad6..42d7e9eaf1ef6f213c43b246170330a7f16d5d7a 100644
--- a/ip/ipifc.c
+++ b/ip/ipifc.c
@@ -135,7 +135,11 @@ ipifcbind(Conv *c, char **argv, int argc)
 	ifc->m = m;
 	ifc->minmtu = ifc->m->minmtu;
 	ifc->maxmtu = ifc->m->maxmtu;
-	ifc->conv->inuse++;
+	if(ifc->m->unbindonclose == 0){
+		lock(ifc->conv);
+		ifc->conv->inuse++;
+		unlock(ifc->conv);
+	}
 	ifc->ifcid++;
 
 	wunlock(ifc);
@@ -161,11 +165,15 @@ ipifcunbind(Ipifc *ifc)
 	wlock(ifc);
 
 	/* dissociate routes */
-	ifc->conv->inuse--;
+	if(ifc->m != nil && ifc->m->unbindonclose == 0){
+		lock(ifc->conv);
+		ifc->conv->inuse--;
+		unlock(ifc->conv);
+	}
 	ifc->ifcid++;
 
 	/* disassociate device */
-	if(ifc->m)
+	if(ifc->m != nil && ifc->m->unbind)
 		(*ifc->m->unbind)(ifc);
 	memset(ifc->dev, 0, sizeof(ifc->dev));
 	ifc->arg = nil;
@@ -188,6 +196,7 @@ ipifcunbind(Ipifc *ifc)
 	ifc->m = nil;
 	wunlock(ifc);
 	poperror();
+
 	return nil;
 }
 
@@ -294,7 +303,7 @@ ipifcclose(Conv *c)
 
 	ifc = (Ipifc*)c->ptcl;
 	m = ifc->m;
-	if(m == nil || m->unbindonclose)
+	if(m != nil && m->unbindonclose)
 		ipifcunbind(ifc);
 	unlock(c);
 }
diff --git a/pc/devata.c b/pc/devata.c
index 20bd622761e91e6e1f58e22567c77f10367c4898..e627077ec7295ba8957a0761c6c804c6c19ffb14 100644
--- a/pc/devata.c
+++ b/pc/devata.c
@@ -669,7 +669,6 @@ ataread(Chan* c, void* a, long n, vlong off)
 			atapipart(dp);
 		qunlock(dp);
 		poperror();
-		return atapirwio(c, a, n, off, Cread2);
 	}
 	pp = &dp->p[PART(c->qid.path)];
 
@@ -681,7 +680,10 @@ ataread(Chan* c, void* a, long n, vlong off)
 
 	skip = off % dp->bytes;
 	for(rv = 0; rv < n; rv += i){
-		i = ataxfer(dp, pp, Cread, off+rv-skip, n-rv+skip, buf);
+		if(dp->atapi)
+			i = atapirwio(c, buf, n-rv+skip, off+rv-skip, Cread2);
+		else
+			i = ataxfer(dp, pp, Cread, off+rv-skip, n-rv+skip, buf);
 		if(i == 0)
 			break;
 		i -= skip;
@@ -1674,7 +1676,7 @@ atapiexec(Drive *dp)
 	}
 	
 	ILOCK(&cp->reglock);
-	cp->nsecs = 1;
+	cp->count = 0;
 	cp->sofar = 0;
 	cp->error = 0;
 	cp->cmd = Cpktcmd;
@@ -1734,8 +1736,8 @@ atapireqsense(Drive* dp)
 		return;
 	}
 
+	cp->nsecs = 1;
 	cp->len = 18;
-	cp->count = 0;
 	memset(cp->cmdblk, 0, sizeof(cp->cmdblk));
 	cp->cmdblk[0] = Creqsense;
 	cp->cmdblk[4] = 18;
@@ -1751,19 +1753,23 @@ atapireqsense(Drive* dp)
 }
 
 static long
-atapiio(Drive *dp, uchar *a, ulong len, vlong off, int cmd)
+atapiio(Drive *dp, uchar *buf, ulong len, vlong off, int cmd)
 {
-	ulong bn, n, o, m;
+	ulong start;
 	Controller *cp;
-	uchar *buf;
 	int retrycount;
 
-	cp = dp->cp;
+	/*
+	 *  cut transfer size down to disk buffer size
+	 */
+	start = off / dp->bytes;
+	if(len > Maxxfer)
+		len = Maxxfer;
+	len = (len + dp->bytes - 1) / dp->bytes;
+	if(len == 0)
+		return 0;
 
-	if(cmd == Cread2)
-		buf = smalloc(Maxxfer);
-	else
-		buf = 0;
+	cp = dp->cp;
 	qlock(cp->ctlrlock);
 	retrycount = 2;
 
@@ -1780,55 +1786,35 @@ retry:
 			}
 		}
 		cp->dp = 0;
-		if(cmd == Cread2)
-			free(buf);
+		cp->buf = 0;
 		qunlock(cp->ctlrlock);
 		nexterror();
 	}
 
-	if(cmd == Cread2)
-		cp->buf = buf;
-	else
-		cp->buf = a;
+	cp->buf = buf;
+	cp->nsecs = len;
+	cp->len = len*dp->bytes;
+	cp->cmd = cmd;
 	cp->dp = dp;
-	cp->len = dp->bytes;
 
-	n = len;
-	while(n > 0){
-		bn = off / dp->bytes;
-		if(off > dp->cap-dp->bytes)
-			break;
-		o = off % dp->bytes;
-		m = dp->bytes - o;
-		if(m > n)
-			m = n;
-		memset(cp->cmdblk, 0, 12);
-		cp->cmdblk[0] = cmd;
-		cp->cmdblk[2] = bn >> 24;
-		cp->cmdblk[3] = bn >> 16;
-		cp->cmdblk[4] = bn >> 8;
-		cp->cmdblk[5] = bn;
-		cp->cmdblk[7] = 0;
-		cp->cmdblk[8] = 1;
-		atapiexec(dp);
-		if(cp->count != dp->bytes){
-			print("short read\n");
-			break;
-		}
-		if(cmd == Cread2)
-			memmove(a, cp->buf + o, m);
-		else
-			cp->buf += m;
-		n -= m;
-		off += m;
-		a += m;
-	}
-	poperror();
-	if(cmd == Cread2)
-		free(buf);
+	memset(cp->cmdblk, 0, 12);
+	cp->cmdblk[0] = cmd;
+	cp->cmdblk[2] = start>>24;
+	cp->cmdblk[3] = start>>16;
+	cp->cmdblk[4] = start>>8;
+	cp->cmdblk[5] = start;
+	cp->cmdblk[7] = cp->nsecs>>8;
+	cp->cmdblk[8] = cp->nsecs;
+	atapiexec(dp);
+	if(cp->count != cp->len)
+		print("short read\n");
 	cp->dp = 0;
+	cp->buf = 0;
+	len = cp->count;
 	qunlock(cp->ctlrlock);
-	return len-n;
+	poperror();
+
+	return len;
 }
 
 static long
@@ -1901,8 +1887,8 @@ retry:
 	cp->buf = buf;
 	cp->dp = dp;
 
+	cp->nsecs = 1;
 	cp->len = 18;
-	cp->count = 0;
 	memset(cp->cmdblk, 0, sizeof(cp->cmdblk));
 	cp->cmdblk[0] = Creqsense;
 	cp->cmdblk[4] = 18;
@@ -1914,8 +1900,8 @@ retry:
 		error(Eio);
 	}
 
+	cp->nsecs = 1;
 	cp->len = 8;
-	cp->count = 0;
 	memset(cp->cmdblk, 0, sizeof(cp->cmdblk));
 	cp->cmdblk[0] = Ccapacity;
 	atapiexec(dp);
@@ -1946,7 +1932,6 @@ atapiintr(Controller *cp)
 {
 	uchar cause;
 	int count, loop, pbase;
-	uchar *addr;
 
 	pbase = cp->pbase;
 	cause = inb(pbase+Pcount) & 0x03;
@@ -1966,8 +1951,7 @@ atapiintr(Controller *cp)
 
 	case 0:						/* data out */
 	case 2:						/* data in */
-		addr = cp->buf;
-		if(addr == 0){
+		if(cp->buf == 0){
 			cp->lastcmd = cp->cmd;
 			cp->cmd = 0;
 			if(cp->status & Serr)
@@ -1993,14 +1977,13 @@ atapiintr(Controller *cp)
 			break;
 		}
 		count = inb(pbase+Pcyllsb)|(inb(pbase+Pcylmsb)<<8);
-		if (count > Maxxfer) 
-			count = Maxxfer;
+		if(cp->count+count > Maxxfer)
+			panic("hd%d: count %d, already %d\n", count, cp->count);
 		if(cause == 0)
-			outss(pbase+Pdata, addr, count/2);
+			outss(pbase+Pdata, cp->buf+cp->count, count/2);
 		else
-			inss(pbase+Pdata, addr, count/2);
-		cp->count = count;
-		cp->lastcmd = cp->cmd; 
+			inss(pbase+Pdata, cp->buf+cp->count, count/2);
+		cp->count += count;
 		break;
 
 	case 3:						/* status */
diff --git a/pc/trap.c b/pc/trap.c
index 79286fbfb7b74c65c5a5a65c8373a8c8472d0d66..89f35084063497c13c3e36743ea81117d3a69c7d 100644
--- a/pc/trap.c
+++ b/pc/trap.c
@@ -140,17 +140,6 @@ trap(Ureg* ureg)
 		up->dbgreg = ureg;
 	}
 
-{
-ulong x, y;
-
-if(up)
-  x = (ulong)(up->kstack);
-else
-  x = (ulong)(m->stack);
-y = (ulong)&mach;
-if(y < x+512) panic("cpu%d: trap: kstack %lux %lux", m->machno, x, y);
-}
-
 	v = ureg->trap;
 	if(ctl = irqctl[v]){
 		if(ctl->isintr){
@@ -167,12 +156,22 @@ if(y < x+512) panic("cpu%d: trap: kstack %lux %lux", m->machno, x, y);
 		if(ctl->eoi)
 			ctl->eoi(v);
 
-		/* preemptive scheduling */
+		/* 
+		 *  preemptive scheduling.  to limit stack depth,
+		 *  make sure process has a chance to return from
+		 *  the current interrupt before being preempted a
+		 *  second time.
+		 */
 		if(ctl->isintr && v != VectorTIMER && v != VectorCLOCK)
 		if(up && up->state == Running)
 		if(anyhigher())
-		if(!active.exiting)
+		if(up->preempted == 0)
+		if(!active.exiting){
+			up->preempted = 1;
 			sched();
+			splhi();
+			up->preempted = 0;
+		}
 	}
 	else if(v <= 16 && user){
 		spllo();
diff --git a/port/portdat.h b/port/portdat.h
index faffcd3ce94f65ebdf2f165641131fbf1ca1e66b..1c5695638a9d37553f2d3b7754cdd0ea8648b3b1 100644
--- a/port/portdat.h
+++ b/port/portdat.h
@@ -611,6 +611,9 @@ struct Proc
 	ulong	movetime;	/* last time process switched processors */
 	ulong	readytime;	/* time process went ready */
 	ulong	lockpri;	/* priority of process holding lock we're trying for */
+	int	preempted;	/* true if this process hasn't finished the interrupt
+				 *  that last preempted it
+				 */
 
 	void	*ureg;		/* User registers for notes */
 	void	*dbgreg;	/* User registers for devproc */