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From: joana@hp-vcd.HP.COM (Joan Armstrong)
Newsgroups: comp.unix.wizards
Subject: Re: hp-ux 7.0/800 select() strangeness?
Message-ID: <1760001@hp-vcd.HP.COM>
Date: 31 Aug 90 18:22:38 GMT
References: <90242.151955MAH@awiwuw11.wu-wien.ac.at>
Organization: Hewlett Packard, Vancouver, WA
Lines: 26

Michael Haberler reports:
>I have encountered a strange behaviour of several programs which use
>select(2) on hp-ux 7.0 on the Series 800. All of these programs are
>'ported' BSD code, so I have the suspicion there's something in common:
>
>It seems that programs which have select(2) in their inner loop sometimes
>start using enormous amounts of system cpu time, just as if the select()
>call would return immediately as if it were polling. Among those programs
>are Xemacs 18.55, Greg Minshall's tn3270, and named4.8.3.
>
>Since several programs show this behaviour, I suspect it  has to do with the
>way select() is implemented in hpux 7.0.
>
>Has anybody else encountered this behaviour? Is this a bug? If so, is there
>a workaround?

We noticed this when upgrading to HP-UX 6.5 (same in 7.0) ... our situation 
involves a realtime control program using a select to read pipe variables.  
If the specified pipe was not writing, the select would fall thru, 
effectively polling. Yucky.  Our fix is not generic, but we just check 
to see that all the select'ed pipes are indeed alive.  Sorry, this fix
probably isn't much help.

--Joan

HP Vancouver Division