.\"	$OpenBSD: hardclock.9,v 1.8 2007/05/31 19:20:00 jmc Exp $
.\"
.\" Copyright (c) 2001 Kenneth R Westerback
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.Dd $Mdocdate: May 31 2007 $
.Dt HARDCLOCK 9
.Os
.Sh NAME
.Nm hardclock
.Nd real-time system clock
.Sh SYNOPSIS
.Fd #include <sys/systm.h>
.Ft void
.Fo "hardclock"
.Fa "struct clockframe *frame"
.Fc
.Sh DESCRIPTION
.Fn hardclock
implements the real-time system clock, interrupting
.Xr hz 9
times a second.
The argument
.Fa frame
is an opaque, machine dependent structure that encapsulates the
previous machine state.
.Pp
.Fn hardclock
performs a variety of time related housekeeping tasks, such as
.Bl -bullet -offset indent
.It
If the current process has virtual or profiling interval
timers, update the timers and deliver appropriate signals.
.It
If there is no separate statistics clock, execute
.Fn statclock .
.It
Increment the time of day, implementing any adjustments requested by
.Xr adjtime 2
or required as a result of running an NTP daemon or other configured
external clock.
.It
Update the real-time timeout queue, calling
.Fn softclock
directly if the current interrupt priority is low enough.
.El
.Sh CODE REFERENCES
.Fn hardclock
is implemented in the file
.Pa sys/kern/kern_clock.c .
.Sh SEE ALSO
.Xr adjtime 2 ,
.Xr hz 9 ,
.Xr microtime 9 ,
.Xr spl 9 ,
.Xr time 9 ,
.Xr timeout 9