In arm_get_next_irq(), use the last IRQ argument in order to prevent

a hard hang due to an interrupt storm or stuck interrupt pin. We
return the next IRQ that is larger than the last one returned and
in doing so give all interrupts a fair chance of being handled.
Consequently, we're able to break into the kernel debugger in such
an event.

1 files changed, 23 insertions, 11 deletions

diff --git a/sys/arm/mv/ic.c b/sys/arm/mv/ic.c
index 83d43a1..14c6b7b 100644
--- a/sys/arm/mv/ic.c
+++ b/sys/arm/mv/ic.c
@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/systm.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
+#include <sys/ktr.h>
 #include <sys/module.h>
 #include <sys/rman.h>
 #include <machine/bus.h>
@@ -143,27 +144,38 @@ static devclass_t mv_ic_devclass;
 DRIVER_MODULE(ic, simplebus, mv_ic_driver, mv_ic_devclass, 0, 0);
 
 int
-arm_get_next_irq(int last __unused)
+arm_get_next_irq(int last)
 {
-	int irq;
+	u_int filt, irq;
+	int next;
 
+	filt = ~((last >= 0) ? (2 << last) - 1 : 0);
 	irq = mv_ic_get_cause() & mv_ic_get_mask();
-	if (irq)
-		return (ffs(irq) - 1);
-
+	if (irq & filt) {
+		next = ffs(irq & filt) - 1;
+		goto out;
+	}
 	if (mv_ic_sc->ic_high_regs) {
+		filt = ~((last >= 32) ? (2 << (last - 32)) - 1 : 0);
 		irq = mv_ic_get_cause_hi() & mv_ic_get_mask_hi();
-		if (irq)
-			return (ffs(irq) + 31);
+		if (irq & filt) {
+			next = ffs(irq & filt) + 31;
+			goto out;
+		}
 	}
-
 	if (mv_ic_sc->ic_error_regs) {
+		filt = ~((last >= 64) ? (2 << (last - 64)) - 1 : 0);
 		irq = mv_ic_get_cause_error() & mv_ic_get_mask_error();
-		if (irq)
-			return (ffs(irq) + 63);
+		if (irq & filt) {
+			next = ffs(irq & filt) + 63;
+			goto out;
+		}
 	}
+	next = -1;
 
-	return (-1);
+ out:
+	CTR3(KTR_INTR, "%s: last=%d, next=%d", __func__, last, next);
+	return (next);
 }
 
 static void