patch-2.2.10 linux/arch/alpha/kernel/time.c

• Lines: 174
• Date: Sat Jun 12 11:52:52 1999
• Orig file: v2.2.9/linux/arch/alpha/kernel/time.c
• Orig date: Wed Apr 28 11:37:29 1999

diff -u --recursive --new-file v2.2.9/linux/arch/alpha/kernel/time.c linux/arch/alpha/kernel/time.c
@@ -1,7 +1,7 @@
 /*
  *  linux/arch/alpha/kernel/time.c
  *
- *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
+ *  Copyright (C) 1991, 1992, 1995, 1999  Linus Torvalds
  *
  * This file contains the PC-specific time handling details:
  * reading the RTC at bootup, etc..
@@ -42,6 +42,9 @@
 #include "proto.h"
 #include "irq.h"
 
+extern rwlock_t xtime_lock;
+extern volatile unsigned long lost_ticks;	/* kernel/sched.c */
+
 static int set_rtc_mmss(unsigned long);
 
 
@@ -86,15 +89,15 @@
 	long nticks;
 
 #ifdef __SMP__
-	extern void smp_percpu_timer_interrupt(struct pt_regs *);
-	extern unsigned int boot_cpu_id;
-	/* when SMP, do this for *all* CPUs, 
-	   but only do the rest for the boot CPU */
+	/* When SMP, do this for *all* CPUs, but only do the rest for
+           the boot CPU.  */
 	smp_percpu_timer_interrupt(regs);
-	if (smp_processor_id() != boot_cpu_id)
-	  return;
+	if (smp_processor_id() != smp_boot_cpuid)
+		return;
 #endif
 
+	write_lock(&xtime_lock);
+
 	/*
 	 * Calculate how many ticks have passed since the last update,
 	 * including any previous partial leftover.  Save any resulting
@@ -124,6 +127,8 @@
 		int tmp = set_rtc_mmss(xtime.tv_sec);
 		state.last_rtc_update = xtime.tv_sec - (tmp ? 600 : 0);
 	}
+
+	write_unlock(&xtime_lock);
 }
 
 /*
@@ -226,7 +231,8 @@
 {
 	void (*irq_handler)(int, void *, struct pt_regs *);
 	unsigned int year, mon, day, hour, min, sec, cc1, cc2;
-	unsigned long cycle_freq, diff, one_percent;
+	unsigned long cycle_freq, one_percent;
+	long diff;
 
 	/*
 	 * The Linux interpretation of the CMOS clock register contents:
@@ -242,7 +248,7 @@
 
 	if (!est_cycle_freq) {
 		/* Sometimes the hwrpb->cycle_freq value is bogus. 
-	   	Go another round to check up on it and see.  */
+		   Go another round to check up on it and see.  */
 		do { } while (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP));
 		do { } while (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP);
 		cc2 = rpcc();
@@ -279,8 +285,7 @@
 	mon = CMOS_READ(RTC_MONTH);
 	year = CMOS_READ(RTC_YEAR);
 
-	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
-	{
+	if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD) {
 		BCD_TO_BIN(sec);
 		BCD_TO_BIN(min);
 		BCD_TO_BIN(hour);
@@ -328,18 +333,24 @@
 void
 do_gettimeofday(struct timeval *tv)
 {
-	unsigned long flags, delta_cycles, delta_usec;
-	unsigned long sec, usec;
-	__u32 now;
-	extern volatile unsigned long lost_ticks;	/*kernel/sched.c*/
+	unsigned long sec, usec, lost, flags;
+	unsigned long delta_cycles, delta_usec, partial_tick;
 
-	now = rpcc();
-	save_and_cli(flags);
+	read_lock_irqsave(&xtime_lock, flags);
+
+	delta_cycles = rpcc() - state.last_time;
 	sec = xtime.tv_sec;
 	usec = xtime.tv_usec;
-	delta_cycles = now - state.last_time;
-	restore_flags(flags);
+	partial_tick = state.partial_tick;
+	lost = lost_ticks;
+
+	read_unlock_irqrestore(&xtime_lock, flags);
 
+#ifdef __SMP__
+	/* Until and unless we figure out how to get cpu cycle counters
+	   in sync and keep them there, we can't use the rpcc tricks.  */
+	delta_usec = lost * (1000000 / HZ);
+#else
 	/*
 	 * usec = cycles * ticks_per_cycle * 2**48 * 1e6 / (2**48 * ticks)
 	 *	= cycles * (s_t_p_c) * 1e6 / (2**48 * ticks)
@@ -354,13 +365,10 @@
 	 */
 
 	delta_usec = (delta_cycles * state.scaled_ticks_per_cycle 
-			+ state.partial_tick
-			+ (lost_ticks << FIX_SHIFT) ) * 15625;
+		      + partial_tick
+		      + (lost << FIX_SHIFT)) * 15625;
 	delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
-
-	/* the 'lost_tics' term above implements this:	
-	 * delta_usec += lost_ticks * (1000000 / HZ);
-	 */
+#endif
 
 	usec += delta_usec;
 	if (usec >= 1000000) {
@@ -375,13 +383,41 @@
 void
 do_settimeofday(struct timeval *tv)
 {
-	cli();
-	xtime = *tv;
+	unsigned long delta_usec;
+	long sec, usec;
+	
+	write_lock_irq(&xtime_lock);
+
+	/* The offset that is added into time in do_gettimeofday above
+	   must be subtracted out here to keep a coherent view of the
+	   time.  Without this, a full-tick error is possible.  */
+
+#ifdef __SMP__
+	delta_usec = lost_ticks * (1000000 / HZ);
+#else
+	delta_usec = rpcc() - state.last_time;
+	delta_usec = (delta_usec * state.scaled_ticks_per_cycle 
+		      + state.partial_tick
+		      + (lost_ticks << FIX_SHIFT)) * 15625;
+	delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
+#endif
+
+	sec = tv->tv_sec;
+	usec = tv->tv_usec;
+	usec -= delta_usec;
+	if (usec < 0) {
+		usec += 1000000;
+		sec -= 1;
+	}
+
+	xtime.tv_sec = sec;
+	xtime.tv_usec = usec;
 	time_adjust = 0;		/* stop active adjtime() */
 	time_status |= STA_UNSYNC;
 	time_maxerror = NTP_PHASE_LIMIT;
 	time_esterror = NTP_PHASE_LIMIT;
-	sti();
+
+	write_unlock_irq(&xtime_lock);
 }