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Path: utzoo!linus!philabs!cmcl2!seismo!mcvax!turing!haring!jim
From: jim@haring.UUCP
Newsgroups: net.unix
Subject: Re: shutdown
Message-ID: <357@haring.UUCP>
Date: Fri, 16-Nov-84 10:33:23 EST
Article-I.D.: haring.357
Posted: Fri Nov 16 10:33:23 1984
Date-Received: Sat, 17-Nov-84 19:59:51 EST
References: <592@denelcor.UUCP>
Organization: CWI, Amsterdam
Lines: 12
Apparently-To: rnews@turing.LOCAL

Shutdown attempts to write to everyone's terminal. Now, someone
can block that message (with a ^S or whatever) and the write
hangs. Shutdown has an alarm() round the write, to arrange to
catch such action. However, the alarm handling routine 'does
nothing', it is only to interrupt the write system call, but,
since on 4.2, the write system call is restartable, you go back
to where you were...

You need to have a setjmp/longjmp construct instead. Later versions
of 4.2 have this fixed.

Jim McKie    Centrum voor Wiskunde en Informatica, Amsterdam    mcvax!jim