/*
* Adjust the time obtained from the CMOS to be UTC time instead of
* local time.
*
* This is ugly, but preferable to the alternatives. Otherwise we
* would either need to write a program to do it in /etc/rc (and risk
* confusion if the program gets run more than once; it would also be
* hard to make the program warp the clock precisely n hours) or
* compile in the timezone information into the kernel. Bad, bad....
*
* - TYT, 1992-01-01
*
* The best thing to do is to keep the CMOS clock in universal time (UTC)
* as real UNIX machines always do it. This avoids all headaches about
* daylight saving times and warping kernel clocks.
*/
inline static void warp_clock(void)
{
write_seqlock_irq(&xtime_lock);
wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
xtime.tv_sec += sys_tz.tz_minuteswest * 60;
time_interpolator_update(sys_tz.tz_minuteswest * 60 * NSEC_PER_SEC);
write_sequnlock_irq(&xtime_lock);
clock_was_set();
}
/* * this routine handles the overflow of the microsecond field * * The tricky bits of code to handle the accurate clock support * were provided by Dave Mills ([email protected]) of NTP fame. * They were originally developed for SUN and DEC kernels. * All the kudos should go to Dave for this stuff. */ void second_overflow(void) { long time_adj; /* Bump the maxerror field */ time_maxerror += MAXFREQ >> SHIFT_USEC; if (time_maxerror > NTP_PHASE_LIMIT) { time_maxerror = NTP_PHASE_LIMIT; time_status |= STA_UNSYNC; } /* * Leap second processing. If in leap-insert state at the end of the * day, the system clock is set back one second; if in leap-delete * state, the system clock is set ahead one second. The microtime() * routine or external clock driver will insure that reported time is * always monotonic. The ugly divides should be replaced. */ switch (time_state) { case TIME_OK: if (time_status & STA_INS) time_state = TIME_INS; else if (time_status & STA_DEL) time_state = TIME_DEL; break; case TIME_INS: if (xtime.tv_sec % 86400 == 0) { xtime.tv_sec--; wall_to_monotonic.tv_sec++; /* * The timer interpolator will make time change * gradually instead of an immediate jump by one second */ time_interpolator_update(-NSEC_PER_SEC); time_state = TIME_OOP; printk(KERN_NOTICE "Clock: inserting leap second " "23:59:60 UTC\n"); } break; case TIME_DEL: if ((xtime.tv_sec + 1) % 86400 == 0) { xtime.tv_sec++; wall_to_monotonic.tv_sec--; /* * Use of time interpolator for a gradual change of * time */ time_interpolator_update(NSEC_PER_SEC); time_state = TIME_WAIT; printk(KERN_NOTICE "Clock: deleting leap second " "23:59:59 UTC\n"); } break; case TIME_OOP: time_state = TIME_WAIT; break; case TIME_WAIT: if (!(time_status & (STA_INS | STA_DEL))) time_state = TIME_OK; } /* * Compute the phase adjustment for the next second. The offset is * reduced by a fixed factor times the time constant. */ tick_length = tick_length_base; time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); time_offset -= time_adj; tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); if (unlikely(time_adjust)) { if (time_adjust > MAX_TICKADJ) { time_adjust -= MAX_TICKADJ; tick_length += MAX_TICKADJ_SCALED; } else if (time_adjust < -MAX_TICKADJ) { time_adjust += MAX_TICKADJ; tick_length -= MAX_TICKADJ_SCALED; } else { tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) << TICK_LENGTH_SHIFT; time_adjust = 0; } } }