xref: /freebsd/share/man/man9/hardclock.9 (revision acb1f1269c6f4ff89a0d28ba742f6687e9ef779d)
1.\"	$NetBSD: hardclock.9,v 1.3 2010/03/25 15:17:38 jruoho Exp $
2.\"
3.\" Copyright (c) 2001 The NetBSD Foundation, Inc.
4.\" All rights reserved.
5.\"
6.\" This code is derived from software contributed to The NetBSD Foundation
7.\" by Thomas Klausner.
8.\"
9.\" Redistribution and use in source and binary forms, with or without
10.\" modification, are permitted provided that the following conditions
11.\" are met:
12.\" 1. Redistributions of source code must retain the above copyright
13.\"    notice, this list of conditions and the following disclaimer.
14.\" 2. Redistributions in binary form must reproduce the above copyright
15.\"    notice, this list of conditions and the following disclaimer in the
16.\"    documentation and/or other materials provided with the distribution.
17.\"
18.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
19.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
21.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
22.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
28.\" POSSIBILITY OF SUCH DAMAGE.
29.\"
30.Dd March 25, 2010
31.Dt HARDCLOCK 9
32.Os
33.Sh NAME
34.Nm hardclock
35.Nd real-time timer
36.Sh SYNOPSIS
37.Ft void
38.Fn hardclock "int cnt" "int usermode"
39.Sh DESCRIPTION
40The
41.Fn hardclock
42function is called
43.Xr hz 9
44times per second.
45It implements the real-time system clock.
46The argument
47.Va cnt
48is the estimated number of ticks since the last call to
49.Fn hardclock .
50The argument
51.Va usermode
52is none-zero when
53.Fn hardclock
54is called from a user-mode context.
55.Pp
56.Fn hardclock
57may perform different tasks such as:
58.Bl -bullet -offset indent
59.It
60Run the current process's virtual and profile time (decrease the
61corresponding timers, if they are activated, and generate
62.Li SIGVTALRM
63or
64.Li SIGPROF ,
65respectively).
66.It
67Increment the time-of-day, taking care of any
68.Xr ntpd 8
69or
70.Xr adjtime 2
71induced changes and leap seconds, as well as any necessary
72compensations to keep in sync with PPS signals or external clocks, if
73support for this is in the kernel (see
74.Xr options 4 ) .
75.It
76Schedule softclock interrupts (
77.Xr swi 9 )
78processing.
79.It
80Collect
81.Xr hwpmc 4
82statistics.
83.It
84Do device polling, when enabled.
85.It
86Implement software
87.Xr watchdog 9
88processing.
89.It
90Enqueue
91.Xr epoch 9
92processing.
93.El
94.Sh SEE ALSO
95.Xr adjtime 2 ,
96.Xr ntp_adjtime 2 ,
97.Xr signal 3 ,
98.Xr ntpd 8 ,
99.Xr callout 9 ,
100.Xr hz 9
101