From 2785d1d48786d520936ae90c239ee068b145a018 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 26 Oct 1994 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1994-10-26

---
 carrera/trap.c | 28 +++++++++++++++++++++-------
 port/qio.c     | 18 +++++++++++++++---
 2 files changed, 36 insertions(+), 10 deletions(-)

diff --git a/carrera/trap.c b/carrera/trap.c
index f5901e1f096e49c380643a036b85f9a93c561670..a2eeac275dd628a0ef46d3389d163c025655ab4f 100644
--- a/carrera/trap.c
+++ b/carrera/trap.c
@@ -296,9 +296,28 @@ seteisadma(int ch, void (*func)(void))
 }
 
 void
-intr(Ureg *ur)
+eisadmaintr(void)
 {
 	int i;
+	uchar isr;
+	void (*f)(void);
+
+	isr = EISAINB(Eisadmaintr) & ~(1<<4);
+	for(i = 0; i < 8; i++) {
+		if(isr & 1) {
+			f = eisadma[i];
+			if(f == 0)
+				print("EISAdma%d: stray intr %.2ux\n", i, isr);
+			else
+				f();
+		}
+		isr >>= 1;
+	}
+}
+
+void
+intr(Ureg *ur)
+{
 	static uchar devint;
 	ulong cause = ur->cause;
 	ulong isr, vec;
@@ -368,12 +387,7 @@ intr(Ureg *ur)
 			mpegintr();
 			break;
 		case 13:
-			isr = EISAINB(Eisadmaintr) & ~(1<<4);
-			for(i = 0; i < 8; i++) {
-				if(isr & 1)
-					eisadma[i]();
-				isr >>= 1;
-			}
+			eisadmaintr();
 			break;
 		}
 		cause &= ~INTR4;
diff --git a/port/qio.c b/port/qio.c
index 8765dc5bde6e6b327e587e08522266890522b24a..8d72e4e332fe793531c6552b41eb0bfff3956276 100644
--- a/port/qio.c
+++ b/port/qio.c
@@ -375,15 +375,26 @@ long
 qread(Queue *q, void *vp, int len)
 {
 	Block *b;
-	int n, dowakeup;
+	int n, dowakeup, syncwait;
 	uchar *p = vp;
 
 	qlock(&q->rlock);
+	syncwait = 0;
 	if(waserror()){
 		/* can't let go if the buffer is in use */
-		if(q->syncbuf){
+		if(syncwait){
 			qlock(&q->wlock);
 			ilock(q);
+			if(q->syncbuf == 0){
+				/* we got some data before the interrupt, queue it */
+				b = allocb(q->synclen);
+				memmove(b->wp, vp, q->synclen);
+				b->wp += q->synclen;
+				if(q->bfirst == 0)
+					q->blast = b;
+				q->bfirst = b;
+				q->len += q->synclen;
+			}
 			q->syncbuf = 0;
 			iunlock(q);
 			qunlock(&q->wlock);
@@ -415,10 +426,11 @@ qread(Queue *q, void *vp, int len)
 			q->synclen = len;
 			q->syncbuf = vp;
 			iunlock(q);
+			syncwait = 1; USED(syncwait);
 			sleep(&q->rr, filled, q);
 			len = q->synclen;
-			poperror();
 			qunlock(&q->rlock);
+			poperror();
 			return len;
 		} else {
 			q->state |= Qstarve;