static/netbsd/man4/swwdog.4 4.html


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<table class="head">
  <tr>
    <td class="head-ltitle">SWWDOG(4)</td>
    <td class="head-vol">Device Drivers Manual</td>
    <td class="head-rtitle">SWWDOG(4)</td>
  </tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">swwdog</code> &#x2014; <span class="Nd">software
    watchdog timer</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp"><code class="Cd">pseudo-device swwdog</code></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">swwdog</code> driver provides a software
    watchdog timer that works with <a class="Xr">wdogctl(8)</a>. If the timer
    expires, the system reboots if the boolean variable
    <var class="Va">swwdog_reboot</var> is <code class="Dv">true</code>;
    otherwise, the system will panic. <var class="Va">swwdog_reboot</var> is
    accessible as the <a class="Xr">sysctl(8)</a> variable hw.swwdog.reboot and
    defaults to <code class="Dv">false</code>.</p>
<p class="Pp">The default period of <code class="Nm">swwdog</code> is 60
    seconds.</p>
<p class="Pp">As with other watchdog timers, the <code class="Nm">swwdog</code>
    driver prevents a system from suspending when the watchdog is armed.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
  ALSO</a></h1>
<p class="Pp"><a class="Xr">sysctl(8)</a>, <a class="Xr">wdogctl(8)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">swwdog</code> driver was written by
    <span class="An">Steven M. Bellovin</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="BUGS"><a class="permalink" href="#BUGS">BUGS</a></h1>
<p class="Pp">Only one watchdog timer can be active at any given time.
    (Arguably, this is a bug in the watchdog timer framework.) Therefore, only a
    single instance of the <code class="Nm">swwdog</code> device can be
  created.</p>
<p class="Pp">Kernel tickle mode is useless with <code class="Nm">swwdog</code>
    and arguably should be rejected, since both it and this driver rely on the
    same callout mechanism; if one is blocked, almost certainly the other is as
    well.</p>
<p class="Pp">The alarm option to <a class="Xr">wdogctl(8)</a> isn't
    implemented.</p>
</section>
</div>
<table class="foot">
  <tr>
    <td class="foot-date">June 8, 2011</td>
    <td class="foot-os">NetBSD 10.1</td>
  </tr>
</table>