diff -urN 2.2.15pre13/arch/alpha/kernel/alpha_ksyms.c rtc/arch/alpha/kernel/alpha_ksyms.c
--- 2.2.15pre13/arch/alpha/kernel/alpha_ksyms.c	Fri Jan  7 18:19:06 2000
+++ rtc/arch/alpha/kernel/alpha_ksyms.c	Tue Mar  7 03:18:43 2000
@@ -37,6 +37,7 @@
 extern struct hwrpb_struct *hwrpb;
 extern void dump_thread(struct pt_regs *, struct user *);
 extern int dump_fpu(struct pt_regs *, elf_fpregset_t *);
+extern spinlock_t rtc_lock;
 
 /* these are C runtime functions with special calling conventions: */
 extern void __divl (void);
@@ -184,6 +185,8 @@
 EXPORT_SYMBOL(local_bh_count);
 EXPORT_SYMBOL(local_irq_count);
 #endif /* __SMP__ */
+
+EXPORT_SYMBOL(rtc_lock);
 
 /*
  * The following are special because they're not called
diff -urN 2.2.15pre13/arch/alpha/kernel/time.c rtc/arch/alpha/kernel/time.c
--- 2.2.15pre13/arch/alpha/kernel/time.c	Sun Jan  2 18:26:32 2000
+++ rtc/arch/alpha/kernel/time.c	Tue Mar  7 03:18:27 2000
@@ -47,6 +47,7 @@
 
 static int set_rtc_mmss(unsigned long);
 
+spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
 
 /*
  * Shift amount by which scaled_ticks_per_cycle is scaled.  Shifting
@@ -443,6 +444,8 @@
 	int real_seconds, real_minutes, cmos_minutes;
 	unsigned char save_control, save_freq_select;
 
+	/* irq are locally disabled here */
+	spin_lock(&rtc_lock);
 	/* Tell the clock it's being set */
 	save_control = CMOS_READ(RTC_CONTROL);
 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
@@ -492,6 +495,7 @@
 	 */
 	CMOS_WRITE(save_control, RTC_CONTROL);
 	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+	spin_unlock(&rtc_lock);
 
 	return retval;
 }
diff -urN 2.2.15pre13/arch/i386/kernel/i386_ksyms.c rtc/arch/i386/kernel/i386_ksyms.c
--- 2.2.15pre13/arch/i386/kernel/i386_ksyms.c	Mon Jan 17 16:44:33 2000
+++ rtc/arch/i386/kernel/i386_ksyms.c	Tue Mar  7 03:19:01 2000
@@ -20,6 +20,7 @@
 
 extern void dump_thread(struct pt_regs *, struct user *);
 extern int dump_fpu(elf_fpregset_t *);
+extern spinlock_t rtc_lock;
 
 #if defined(CONFIG_BLK_DEV_IDE) || defined(CONFIG_BLK_DEV_HD) || defined(CONFIG_BLK_DEV_IDE_MODULE) || defined(CONFIG_BLK_DEV_HD_MODULE)
 extern struct drive_info_struct drive_info;
@@ -119,3 +120,5 @@
 #ifdef CONFIG_VT
 EXPORT_SYMBOL(screen_info);
 #endif
+
+EXPORT_SYMBOL(rtc_lock);
diff -urN 2.2.15pre13/arch/i386/kernel/time.c rtc/arch/i386/kernel/time.c
--- 2.2.15pre13/arch/i386/kernel/time.c	Sat Mar  4 18:02:00 2000
+++ rtc/arch/i386/kernel/time.c	Tue Mar  7 03:18:27 2000
@@ -78,6 +78,8 @@
 
 extern rwlock_t xtime_lock;
 
+spinlock_t rtc_lock = SPIN_LOCK_UNLOCKED;
+
 static inline unsigned long do_fast_gettimeoffset(void)
 {
 	register unsigned long eax asm("ax");
@@ -301,6 +303,8 @@
 	int real_seconds, real_minutes, cmos_minutes;
 	unsigned char save_control, save_freq_select;
 
+	/* gets recalled with irq locally disabled */
+	spin_lock(&rtc_lock);
 	save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
 	CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
 
@@ -346,6 +350,7 @@
 	 */
 	CMOS_WRITE(save_control, RTC_CONTROL);
 	CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
+	spin_unlock(&rtc_lock);
 
 	return retval;
 }
diff -urN 2.2.15pre13/drivers/char/rtc.c rtc/drivers/char/rtc.c
--- 2.2.15pre13/drivers/char/rtc.c	Sun Jan  2 18:26:37 2000
+++ rtc/drivers/char/rtc.c	Tue Mar  7 03:18:27 2000
@@ -113,10 +113,15 @@
 unsigned char days_in_mo[] = 
 {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
 
+extern spinlock_t rtc_lock;
+
 /*
  *	A very tiny interrupt handler. It runs with SA_INTERRUPT set,
- *	so that there is no possibility of conflicting with the
- *	set_rtc_mmss() call that happens during some timer interrupts.
+ *	but there is possibility of conflicting with the set_rtc_mmss()
+ *	call (the rtc irq and the timer irq can easily run at the same
+ *	time in two different CPUs). So we need to serializes
+ *	accesses to the chip with the rtc_lock spinlock that each
+ *	architecture should implement in the timer code.
  *	(See ./arch/XXXX/kernel/time.c for the set_rtc_mmss() function.)
  */
 
@@ -131,7 +136,10 @@
 
 	rtc_irq_data += 0x100;
 	rtc_irq_data &= ~0xff;
+	/* runs with irq locally disabled (see SA_INTERRUPT flag). */
+	spin_lock(&rtc_lock);
 	rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);
+	spin_unlock(&rtc_lock);
 	wake_up_interruptible(&rtc_wait);	
 
 	if (rtc_status & RTC_TIMER_ON)
@@ -276,8 +284,7 @@
 		if (sec >= 60)
 			sec = 0xff;
 
-		save_flags(flags);
-		cli();
+		spin_lock_irqsave(&rtc_lock, flags);
 		if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) ||
 		    RTC_ALWAYS_BCD)
 		{
@@ -288,7 +295,7 @@
 		CMOS_WRITE(hrs, RTC_HOURS_ALARM);
 		CMOS_WRITE(min, RTC_MINUTES_ALARM);
 		CMOS_WRITE(sec, RTC_SECONDS_ALARM);
-		restore_flags(flags);
+		spin_unlock_irqrestore(&rtc_lock, flags);
 
 		return 0;
 	}
@@ -336,12 +343,11 @@
 		if ((yrs -= epoch) > 255)    /* They are unsigned */
 			return -EINVAL;
 
-		save_flags(flags);
-		cli();
+		spin_lock_irqsave(&rtc_lock, flags);
 		if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY)
 		    || RTC_ALWAYS_BCD) {
 			if (yrs > 169) {
-				restore_flags(flags);
+				spin_unlock_irqrestore(&rtc_lock, flags);
 				return -EINVAL;
 			}
 			if (yrs >= 100)
@@ -370,7 +376,7 @@
 		CMOS_WRITE(save_control, RTC_CONTROL);
 		CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
 
-		restore_flags(flags);
+		spin_unlock_irqrestore(&rtc_lock, flags);
 		return 0;
 	}
 	case RTC_IRQP_READ:	/* Read the periodic IRQ rate.	*/
@@ -405,12 +411,11 @@
 
 		rtc_freq = arg;
 
-		save_flags(flags);
-		cli();
+		spin_lock_irqsave(&rtc_lock, flags);
 		val = CMOS_READ(RTC_FREQ_SELECT) & 0xf0;
 		val |= (16 - tmp);
 		CMOS_WRITE(val, RTC_FREQ_SELECT);
-		restore_flags(flags);
+		spin_unlock_irqrestore(&rtc_lock, flags);
 		return 0;
 	}
 #ifdef __alpha__
@@ -465,15 +470,14 @@
 	unsigned char tmp;
 	unsigned long flags;
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	tmp = CMOS_READ(RTC_CONTROL);
 	tmp &=  ~RTC_PIE;
 	tmp &=  ~RTC_AIE;
 	tmp &=  ~RTC_UIE;
 	CMOS_WRITE(tmp, RTC_CONTROL);
 	CMOS_READ(RTC_INTR_FLAGS);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 
 	if (rtc_status & RTC_TIMER_ON) {
 		rtc_status &= ~RTC_TIMER_ON;
@@ -546,11 +550,10 @@
 		while (jiffies - uip_watchdog < 2*HZ/100)
 			barrier();
 	
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	year = CMOS_READ(RTC_YEAR);
 	ctrl = CMOS_READ(RTC_CONTROL);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 	
 	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 		BCD_TO_BIN(year);       /* This should never happen... */
@@ -568,11 +571,10 @@
 	init_timer(&rtc_irq_timer);
 	rtc_irq_timer.function = rtc_dropped_irq;
 	rtc_wait = NULL;
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	/* Initialize periodic freq. to CMOS reset default, which is 1024Hz */
 	CMOS_WRITE(((CMOS_READ(RTC_FREQ_SELECT) & 0xF0) | 0x06), RTC_FREQ_SELECT);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 	rtc_freq = 1024;
 	return 0;
 }
@@ -596,12 +598,11 @@
 	printk(KERN_INFO "rtc: lost some interrupts at %ldHz.\n", rtc_freq);
 	mod_timer(&rtc_irq_timer, jiffies + HZ/rtc_freq + 2*HZ/100);
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	rtc_irq_data += ((rtc_freq/HZ)<<8);
 	rtc_irq_data &= ~0xff;
 	rtc_irq_data |= (CMOS_READ(RTC_INTR_FLAGS) & 0xF0);	/* restart */
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 }
 
 /*
@@ -615,11 +616,10 @@
 	unsigned char batt, ctrl;
 	unsigned long flags;
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	batt = CMOS_READ(RTC_VALID) & RTC_VRT;
 	ctrl = CMOS_READ(RTC_CONTROL);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 
 	p = buf;
 
@@ -690,10 +690,9 @@
 	unsigned long flags;
 	unsigned char uip;
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	uip = (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 	return uip;
 }
 
@@ -723,8 +722,7 @@
 	 * RTC has RTC_DAY_OF_WEEK, we ignore it, as it is only updated
 	 * by the RTC when initially set to a non-zero value.
 	 */
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	rtc_tm->tm_sec = CMOS_READ(RTC_SECONDS);
 	rtc_tm->tm_min = CMOS_READ(RTC_MINUTES);
 	rtc_tm->tm_hour = CMOS_READ(RTC_HOURS);
@@ -732,7 +730,7 @@
 	rtc_tm->tm_mon = CMOS_READ(RTC_MONTH);
 	rtc_tm->tm_year = CMOS_READ(RTC_YEAR);
 	ctrl = CMOS_READ(RTC_CONTROL);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 
 	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 	{
@@ -763,13 +761,12 @@
 	 * Only the values that we read from the RTC are set. That
 	 * means only tm_hour, tm_min, and tm_sec.
 	 */
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	alm_tm->tm_sec = CMOS_READ(RTC_SECONDS_ALARM);
 	alm_tm->tm_min = CMOS_READ(RTC_MINUTES_ALARM);
 	alm_tm->tm_hour = CMOS_READ(RTC_HOURS_ALARM);
 	ctrl = CMOS_READ(RTC_CONTROL);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 
 	if (!(ctrl & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
 	{
@@ -794,13 +791,12 @@
 	unsigned char val;
 	unsigned long flags;
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	val = CMOS_READ(RTC_CONTROL);
 	val &=  ~bit;
 	CMOS_WRITE(val, RTC_CONTROL);
 	CMOS_READ(RTC_INTR_FLAGS);
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 	rtc_irq_data = 0;
 }
 
@@ -809,12 +805,11 @@
 	unsigned char val;
 	unsigned long flags;
 
-	save_flags(flags);
-	cli();
+	spin_lock_irqsave(&rtc_lock, flags);
 	val = CMOS_READ(RTC_CONTROL);
 	val |= bit;
 	CMOS_WRITE(val, RTC_CONTROL);
 	CMOS_READ(RTC_INTR_FLAGS);
 	rtc_irq_data = 0;
-	restore_flags(flags);
+	spin_unlock_irqrestore(&rtc_lock, flags);
 }