Module Name: src Committed By: riastradh Date: Thu Sep 22 14:02:45 UTC 2022
Modified Files: src/sbin/wdogctl: wdogctl.8 Log Message: wdogctl(8): Rework prose and markup in man page. No functional change. To generate a diff of this commit: cvs rdiff -u -r1.25 -r1.26 src/sbin/wdogctl/wdogctl.8 Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files.
Modified files: Index: src/sbin/wdogctl/wdogctl.8 diff -u src/sbin/wdogctl/wdogctl.8:1.25 src/sbin/wdogctl/wdogctl.8:1.26 --- src/sbin/wdogctl/wdogctl.8:1.25 Sat Jul 11 12:51:21 2020 +++ src/sbin/wdogctl/wdogctl.8 Thu Sep 22 14:02:45 2022 @@ -1,4 +1,4 @@ -.\" $NetBSD: wdogctl.8,v 1.25 2020/07/11 12:51:21 jruoho Exp $ +.\" $NetBSD: wdogctl.8,v 1.26 2022/09/22 14:02:45 riastradh Exp $ .\" .\" Copyright (c) 2000 Zembu Labs, Inc. .\" All rights reserved. @@ -66,28 +66,30 @@ .Sh DESCRIPTION .Nm is used to manipulate watchdog timers. -Watchdog timers provide a means of ensuring that a system -continues to make progress. -This is accomplished by use of a timer, provided by either hardware or -software; when the timer expires, the watchdog resets the system. -In this case of a hardware watchdog timer, this is accomplished by -asserting the system's hardware reset signal. -In the case of a software watchdog timer, -this is accomplished by calling the kernel's normal reboot path. -In order to prevent the system from rebooting, -something must refresh the timer to prevent it from expiring. +A watchdog timer is a hardware or software timer that resets the system +if it fails to make progress within a prescribed period. +To prevent the system from being reset, something must refresh the +timer to prevent it from expiring. +.Pp +A hardware watchdog timer asserts system's hardware reset signal when +it expires. +A software watchdog timer calls the kernel's s normal reboot path. .Pp The .Nx -kernel provides three basic modes in which watchdog timers may +kernel provides three modes in which watchdog timers may operate: kernel tickle mode, user tickle mode, and external tickle mode. -In kernel tickle mode, a timer in the kernel refreshes the watchdog timer. -In user tickle mode, +.Bl -tag -width "external tickle mode" +.It kernel tickle mode +A timer in the kernel refreshes the watchdog timer. +This ensures kernel threads can make progress within the period of the +watchdog timer. +.It user tickle mode .Nm runs in the background and refreshes the watchdog timer. -In kernel tickle mode, progress of the kernel is ensured. -In user tickle mode, the ability for user programs to run within a known -period of time is ensured. +This ensures user programs can make progress within the period of the +watchdog timer. +.Pp Note that user tickle mode must be used with caution; on a heavily loaded system, the timer may expire accidentally, even though user programs may be making @@ -96,17 +98,19 @@ A user-mode timer is disarmed (if possib unless the timer is activated with the .Fl x option. -.Pp -External-mode watchdogs are similar to user-mode watchdogs, except -that the tickle must be done explicitly by a separate invocation of -the program with the +.It external tickle mode +Similar to user tickle mode, except that the tickle must be done +explicitly by a separate invocation of the program with the .Fl t option. +This allows users to determine the activity whose progress the watchdog +timer checks. +.El .Pp -In the first two modes, an attempt is made to refresh the watchdog timer -in one half the timer's configured period. -That is, if the watchdog timer has a period of 30 seconds, a refresh attempt -is made every 15 seconds. +In kernel and user tickle modes, an attempt is made to refresh the +watchdog timer in one half the timer's configured period. +For example, if the watchdog timer has a period of 30 seconds, a +refresh attempt is made every 15 seconds. .Pp If called without arguments, .Nm @@ -120,7 +124,7 @@ to arm a timer when one is already armed will be displayed and no action will be taken. .Pp The options are as follows: -.Bl -tag -offset indent -width XpXperiodXX +.Bl -tag -width Fl .It Fl A When arming a timer, this flag indicates that an audible alarm is to sound when the watchdog timer expires and resets the system. @@ -159,8 +163,10 @@ in a modified user tickle mode: closing the timer. .El .Sh FILES -.Pa /dev/watchdog --- the system monitor watchdog timer device +.Bl -tag -width "Pa /dev/watchdog" +.It Pa /dev/watchdog +the system monitor watchdog timer device +.El .Sh SEE ALSO .Xr acpiwdrt 4 , .Xr evbarm/iopwdog 4 ,