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HARDCLOCK(9)		 BSD Kernel Developer's Manual		  HARDCLOCK(9)

NAME
     hardclock — real-time timer

SYNOPSIS
     void
     hardclock(struct clockframe *frame);

DESCRIPTION
     The hardclock() function is called hz(9) times per second.	 It implements
     the real-time system clock.  The argument frame is an opaque, machine-
     dependent structure that encapsulates the previous machine state.

     The hardclock() performs different tasks such as:

	   ·   Run the current process's virtual and profile time (decrease
	       the corresponding timers, if they are activated, and generate
	       SIGVTALRM or SIGPROF, respectively).

	   ·   Increment the time-of-day, taking care of any ntpd(8) or
	       adjtime(2) induced changes and leap seconds, as well as any
	       necessary compensations to keep in sync with PPS signals or
	       external clocks, if support for this is in the kernel (see
	       options(4)).

	   ·   Schedule softclock interrupts if any callouts should be trig‐
	       gered (see callout(9)).

SEE ALSO
     adjtime(2), ntp_adjtime(2), signal(7), ntpd(8), callout(9), hz(9)

BSD				March 25, 2010				   BSD

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