Path: utzoo!attcan!uunet!auspex!guy
From: guy@auspex.UUCP (Guy Harris)
Newsgroups: comp.unix.wizards
Subject: Re: Ultrix tape job is unkillable!
Message-ID: <740@auspex.UUCP>
Date: 17 Dec 88 07:03:25 GMT
References: <476@larry.UUCP> <43200057@uicsrd.csrd.uiuc.edu>
Reply-To: guy@auspex.UUCP (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 19

>Is this a problem in the device driver, kernel process management, or
>something else entirely?

I consider it ultimately to be a problem in the device driver, unless
there is *no* software workaround for the problem.  Both in the
tape-drive case where an interrupt may get lost, and the serial port
case where the "close" is waiting for output to drain, but output has
been suspended and the line is sufficiently dead that it's hard to
resume it, you can probably always have some timeout in the driver, but
you don't want to get screwed if the alarm goes off too soon. 

>It seems that if an event is being waited for, there ought to be a way
>to have the OS force the event to occur or fail.

Unfortunately, in general there isn't such a way.  I think some people
may have stuck a "forced wakeup" system call into their systems
(super-user only, I hope!); do a "ps" with the appropriate flags to get
the numeric wait channel ID and then run some program that uses that ID
in such a call.