SIGPWR signal in system v

[John R. MacMillan]

|Does anybody out there have information on the SYS V SIGPWR signal? The man
|says that this signal occurs if there's a power failure. I have a couple of
|questioned which I haven't been able to answer myself:

On the only system I've used that implemented SIGPWR, the signal is
raised when power is _restored_ not just before it goes away.  In the
event of a power loss the kernel alone had any warning and was able to
write memory contents and state info to non-volatile storage.  When
power was restored, the kernel restored the previous state, and sent
SIGPWR to all processes.  I can't remember for certain, but I think
the default handling may have been SIG_IGN, so many processeses
wouldn't even notice the power loss.  Those that caught SIGPWR could
refresh their screens, or whatever.