WD(3) WD(3)
NAME
wd - hardware watchdog timer
SYNOPSIS
bind -a #w /dev
/dev/wdctl
DESCRIPTION
This device presents textual information about hardware
watchdog timers on PCs and some other machines, and allows
user-level control of them. When enabled, a watchdog timer
counts to zero in a few seconds; upon reaching zero, it
resets the machine with an NMI or equivalent. Some process
must periodically restart the watchdog to avoid the NMI and
keep the system alive; watchdog(8) is one such program.
Reads from wdctl yield data of this form:
enabled 3 restarts
or
disabled 3 restarts
Control messages may be written to wdctl and include
`enable', `disable', and `restart'.
The watchdog is disabled at system shutdown, and when the
last open file descriptor for wdctl is closed.
SOURCE
/sys/src/9/port/devwd.c
/sys/src/9/*/*watchdog.c
SEE ALSO
proc(3), watchdog(8)
BUGS
On PCs, to ensure consistent use of one CPU's timers, an
`enable' message wires the issuing process (see proc(3)) to
a CPU, and any subsequent control messages will wire the
issuing processes to that same CPU.