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From: guy@auspex.auspex.com (Guy Harris)
Newsgroups: comp.os.misc
Subject: Re: What constitutes a good OS?
Message-ID: <5259@auspex.auspex.com>
Date: 15 Jan 91 19:08:28 GMT
References: <1991Jan14.042520.18150@acc.stolaf.edu> <5233@auspex.auspex.com> <1628@lee.SEAS.UCLA.EDU>
Organization: Auspex Systems, Santa Clara
Lines: 36

>Any process that catches a signal, would effectively be modifying
>its file protection bits.

Umm, but that's not *all* it's be doing; it's not catching signals *in
general*, it's catching *specific* signals.

>so that a subsequent rm would be able to remove the process.

OK, what does "remove" mean here?  Send SIGKILL?  Send SIGTERM?  Send
SIGABRT?  Send SIGHUP?  Send SIGUSR1? etc..

>Other characters besides 'w' could be used for the different signals;

Such as?  We're talking UNIXoid system here, which gives you, at
present, only 9 protection bits, but more signals.  In addition, it
seems to me to be a rather silly form of overloading to say "oh yeah,
the group execute bit being set means that the process has caught
SIGABRT"; the bits in question wouldn't mean anything *like* what they'd
mean for a plain file.

In fact, even the owner-write bit would have a different meaning; the
"rm" command is what normally asks before removing a file not writable
by the user - the "unlink()" call only cares about the permissions on
the *containing directory*.  I suppose you could make "/proc" a sticky
directory....

>The complexity is thus moved to the file protection bits, which is OK,
>IMO, because by looking at these you could tell beforehand whether or not 
>you'd have to do the equivalent of a kill -9.  Typically, I'll do a 
>kill on a process to find out that it didn't go away, then have to
>do a kill -9 to get rid of it.

The question there is whether the process is *ignoring* SIGTERM, or
*catching* it but just not cleaning up after itself as quickly as you'd
like.  Which one are you suggesting be reflected as missing "owner
write" permission?