diff -urN 2.2.15pre13/arch/i386/kernel/time.c slow-gtod-1/arch/i386/kernel/time.c
--- 2.2.15pre13/arch/i386/kernel/time.c	Sat Mar  4 18:02:00 2000
+++ slow-gtod-1/arch/i386/kernel/time.c	Mon Mar  6 17:48:13 2000
@@ -112,6 +114,8 @@
 
 #ifndef CONFIG_X86_TSC
 
+spinlock_t i8253_lock = SPIN_LOCK_UNLOCKED;
+
 /* This function must be called with interrupts disabled 
  * It was inspired by Steve McCanne's microtime-i386 for BSD.  -- jrs
  * 
@@ -156,6 +160,8 @@
 	 */
 	unsigned long jiffies_t;
 
+	/* gets recalled with irq locally disabled */
+	spin_lock(&i8253_lock);
 	/* timer count may underflow right here */
 	outb_p(0x00, 0x43);	/* latch the count ASAP */
 
@@ -214,6 +220,7 @@
 		}
 	} else
 		jiffies_p = jiffies_t;
+	spin_unlock(&i8253_lock);
 
 	count_p = count;
 
@@ -447,10 +458,19 @@
 
 		rdtscl(last_tsc_low);
 
+#if 0 /*
+       * SUBTLE: this is not necessary from here because it's implicit in the
+       * write xtime_lock.
+       */
+		spin_lock(&i8253_lock);
+#endif
 		outb_p(0x00, 0x43);     /* latch the count ASAP */
 
 		count = inb_p(0x40);    /* read the latched count */
 		count |= inb(0x40) << 8;
+#if 0
+		spin_unlock(&i8253_lock);
+#endif
 
 		count = ((LATCH-1) - count) * TICK_SIZE;
 		delay_at_last_interrupt = (count + LATCH/2) / LATCH;