.\"	$NetBSD: hardclock.9,v 1.3 2010/03/25 15:17:38 jruoho Exp $
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Thomas Klausner.
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.Dd March 25, 2010
.Dt HARDCLOCK 9
.Os
.Sh NAME
.Nm hardclock
.Nd real-time timer
.Sh SYNOPSIS
.Ft void
.Fn hardclock "struct clockframe *frame"
.Sh DESCRIPTION
The
.Fn hardclock
function is called
.Xr hz 9
times per second.
It implements the real-time system clock.
The argument
.Va frame
is an opaque,
machine-dependent structure that encapsulates the previous machine state.
.Pp
The
.Fn hardclock
performs different tasks such as:
.Bl -bullet -offset indent
.It
Run the current process's virtual and profile time (decrease the
corresponding timers, if they are activated, and generate
.Li SIGVTALRM
or
.Li SIGPROF ,
respectively).
.It
Increment the time-of-day, taking care of any
.Xr ntpd 8
or
.Xr 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
.Xr options 4 ) .
.It
Schedule softclock interrupts if any callouts should be triggered (see
.Xr callout 9 ) .
.El
.Sh SEE ALSO
.Xr adjtime 2 ,
.Xr ntp_adjtime 2 ,
.Xr signal 7 ,
.Xr ntpd 8 ,
.Xr callout 9 ,
.Xr hz 9