TODO: Add some ideas on pmon to watchdog chapter.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

TODO.md

@@ -234,14 +234,29 @@ Watchdog
 
 Support for monitoring the health of the system and its processes.
 
-* Add support for a `/dev/watchdog` plugin to replace `watchdogd`
-* Integrate system supervisor to optionally reboot the system when a
-  process stops responding, or when a respawn limit has been reached,
-  as well as when system load gets too high.
-* API for processes to register with the watchdog.
-  - Deeper monitoring of a process' main loop
+* Add support for a `/dev/watchdog` built-in to replace both the BusyBox
+  watchdogd and my own refreshed uClinux-dist adaptation,
+  [watchdogd](https://github.com/troglobit/watchdogd)
+* Add a system supervisor (pmon) to optionally reboot the system when a
+  process stops responding, or when a respawn limit has been reached, as
+  well as when system load gets too high.  For details on UNIX loadavg,
+  see http://stackoverflow.com/questions/11987495/linux-proc-loadavg
+  - Default to 0.7 as MAX recommended load before warning and 0.9 reboot
+* API for processes to register with the watchdog, libwdt
+  - Deeper monitoring of a process' main loop by instrumenting
   - If a process is not heard from within its subscribed period time
     reboot system or restart process.
+  - Add client libwdt library, inspired by old Westermo API and the
+    [libwdt] API published in the [Fritz!Box source dump], take for
+    instance the `fritzbox7170-source-files-04.87-tar.gz` drop and see
+    the `GPL-release_kernel.tgz` in `drivers/char/avm_new/` for the
+    kernel driver, and the `LGPL-GPL-release_target_tools.tgz` in `wdt/`
+    for the userland API.
+  - When a client process (a standard app/daemon instrumented with
+    libwdt calls in its main loop) registers with the watchdog, we raise
+    the RT priority to 98 (just below the kernel watchdog in prio).
+    This to ensure that system monitoring goes before anything else in
+    the system.
 * Separate `/etc/watchdog.conf` configuration file, or a perhaps
   support for `/etc/finit.d/PLUGIN.conf`?
 * Support enable/disable watchdog features:
@@ -266,6 +281,9 @@ Investigation
 * [FHS changes](http://askubuntu.com/questions/57297/why-has-var-run-been-migrated-to-run)
   affecting runtime status, plugins, etc.
 
+[libwdt]:                http://www.wehavemorefun.de/fritzbox/Libwdt.so
+[Fritz!Box source dump]: ftp://ftp.avm.de/fritz.box/fritzbox.fon_wlan_7170/x_misc/opensrc/
+
 <!--
   -- Local Variables:
   -- mode: markdown