xtime_lock vs update_process_times

[linux-2.6-block.git] / arch / m68knommu / kernel / time.c

/*
 *  linux/arch/m68knommu/kernel/time.c
 *
 *  Copyright (C) 1991, 1992, 1995  Linus Torvalds
 *
 * This file contains the m68k-specific time handling details.
 * Most of the stuff is located in the machine specific files.
 *
 * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
 *		"A Kernel Model for Precision Timekeeping" by Dave Mills
 */

#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/profile.h>
#include <linux/time.h>
#include <linux/timex.h>

#include <asm/machdep.h>
#include <asm/irq_regs.h>

#define	TICK_SIZE (tick_nsec / 1000)

static inline int set_rtc_mmss(unsigned long nowtime)
{
	if (mach_set_clock_mmss)
		return mach_set_clock_mmss (nowtime);
	return -1;
}

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "do_timer()" routine every clocktick
 */
irqreturn_t arch_timer_interrupt(int irq, void *dummy)
{
	/* last time the cmos clock got updated */
	static long last_rtc_update=0;

	if (current->pid)
		profile_tick(CPU_PROFILING);

	write_seqlock(&xtime_lock);

	do_timer(1);

	/*
	 * If we have an externally synchronized Linux clock, then update
	 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
	 * called as close as possible to 500 ms before the new second starts.
	 */
	if (ntp_synced() &&
	    xtime.tv_sec > last_rtc_update + 660 &&
	    (xtime.tv_nsec / 1000) >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
	    (xtime.tv_nsec  / 1000) <= 500000 + ((unsigned) TICK_SIZE) / 2) {
	  if (set_rtc_mmss(xtime.tv_sec) == 0)
	    last_rtc_update = xtime.tv_sec;
	  else
	    last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
	}

	write_sequnlock(&xtime_lock);

#ifndef CONFIG_SMP
	update_process_times(user_mode(get_irq_regs()));
#endif
	return(IRQ_HANDLED);
}

void time_init(void)
{
	unsigned int year, mon, day, hour, min, sec;

	if (mach_gettod)
		mach_gettod(&year, &mon, &day, &hour, &min, &sec);
	else
		year = mon = day = hour = min = sec = 0;

	if ((year += 1900) < 1970)
		year += 100;
	xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
	xtime.tv_nsec = 0;
	wall_to_monotonic.tv_sec = -xtime.tv_sec;

	hw_timer_init();
}