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 July 1, 2021 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 periodically based on pending work. 43The rate ranges from 44.Va hz 45times per second on a very busy system, to twice a second on an idle system. 46The 47.Va cnt 48argument reports an estimate of the number of ticks since the last call. 49The sum of 50.Va cnt 51over a second averages 52.Va hz 53over the long haul. 54See 55.Xr hz 9 56for important details over shorter time scales. 57The argument 58.Va usermode 59is none-zero when 60.Fn hardclock 61is called from an context that interrupted usermode execution. 62.Pp 63.Fn hardclock 64may perform different tasks such as: 65.Bl -bullet -offset indent 66.It 67Run the current process's virtual and profile time (decrease the 68corresponding timers, if they are activated, and generate 69.Li SIGVTALRM 70or 71.Li SIGPROF , 72respectively). 73.It 74Increment the time-of-day, taking care of any 75.Xr ntpd 8 76or 77.Xr adjtime 2 78induced changes and leap seconds, as well as any necessary 79compensations to keep in sync with PPS signals or external clocks, if 80support for this is in the kernel (see 81.Xr options 4 ) . 82.It 83Schedule softclock interrupts ( 84.Xr swi 9 ) 85processing. 86.It 87Collect 88.Xr hwpmc 4 89statistics. 90.It 91Do device polling, when enabled. 92.It 93Implement software 94.Xr watchdog 9 95processing. 96.It 97Enqueue 98.Xr epoch 9 99processing. 100.El 101.Sh SEE ALSO 102.Xr adjtime 2 , 103.Xr ntp_adjtime 2 , 104.Xr signal 3 , 105.Xr ntpd 8 , 106.Xr hz 9 107