--- 2.2.11/arch/i386/kernel/irq.c	Thu Aug 12 02:32:28 1999
+++ /tmp/irq.c	Mon Aug 16 19:26:32 1999
@@ -969,14 +969,25 @@
 	unsigned int i;
 	unsigned long delay;
 
+	/* something may have generated an irq long ago and we want to
+	   flush such a longstanding irq before considering it as spurious. */
+	spin_lock_irq(&irq_controller_lock);
+	for (i = NR_IRQS-1; i > 0; i--)
+		if (!irq_desc[i].action)
+			irq_desc[i].handler->startup(i);
+	spin_unlock_irq(&irq_controller_lock);
+
+	/* Wait for longstanding interrupts to trigger. */
+	for (delay = jiffies + HZ/50; time_after(delay, jiffies); )
+		/* about 20ms delay */ synchronize_irq();
+
 	/*
-	 * first, enable any unassigned irqs
+	 * now, set as autodetect any unassigned irqs
 	 */
 	spin_lock_irq(&irq_controller_lock);
 	for (i = NR_IRQS-1; i > 0; i--) {
 		if (!irq_desc[i].action) {
 			irq_desc[i].status |= IRQ_AUTODETECT | IRQ_WAITING;
-			irq_desc[i].handler->startup(i);
 		}
 	}
 	spin_unlock_irq(&irq_controller_lock);