# HG changeset patch
# User Akshat Kumar <seed@mail.nanosouffle.net>
# Date 1326835804 28800
# Node ID 8d84f339223733993701709da97178a91b0fdd3b
# Parent  4725d6a2b123175c157a55cde6444b6323099d98
trap: enable handling of unknown interrupts

Fixes an off-by-one error and allows unknown
interrupts to pass through (taken from Plan 9).
The latter was required to boot nix on my computer,
since it was receiving a spurious interrupts 0x27.

R=nix-dev
CC=nix-dev, noah.evans
http://codereview.appspot.com/5543053

Committer: John Floren <john@jfloren.net>

diff -r 4725d6a2b123 -r 8d84f3392237 sys/src/nix/k10/trap.c
--- a/sys/src/nix/k10/trap.c	Tue Jan 17 13:29:39 2012 -0800
+++ b/sys/src/nix/k10/trap.c	Tue Jan 17 13:30:04 2012 -0800
@@ -359,11 +359,31 @@
 				preempted();
 		}
 	}
-	else if(vno <= nelem(excname) && user){
+	else if(vno < nelem(excname) && user){
 		spllo();
 		sprint(buf, "sys: trap: %s", excname[vno]);
 		postnote(up, 1, buf, NDebug);
 	}
+	else if(vno >= VectorPIC && vno != VectorSYSCALL){
+		/*
+		 * An unknown interrupt.
+		 * Check for a default IRQ7. This can happen when
+		 * the IRQ input goes away before the acknowledge.
+		 * In this case, a 'default IRQ7' is generated, but
+		 * the corresponding bit in the ISR isn't set.
+		 * In fact, just ignore all such interrupts.
+		 */
+
+		/* clear the interrupt */
+		i8259isr(vno);
+
+		iprint("cpu%d: spurious interrupt %d, last %d\n",
+			m->machno, vno, m->lastintr);
+
+		if(user)
+			kexit(ureg);
+		return;
+	}
 	else{
 		if(vno == VectorNMI){
 			nmienable();