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:

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

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

	   o   Schedule softclock interrupts if any callouts should be triggered (see callout(9)).

SEE ALSO

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

BSD
								  March 25, 2010							       BSD