WD(3)WD(3)NAMEwd - 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 and
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 ALSOproc(3), watchdog(8)BUGS
On PCs, to ensure consistent use of one CPU's timers, an 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.
WD(3)