Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!mailrus!uflorida!haven!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: sleeping while at spltty?
Message-ID: <16956@mimsy.UUCP>
Date: 16 Apr 89 11:53:36 GMT
References: <824@twwells.uucp>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 16

In article <824@twwells.uucp> bill@twwells.uucp (T. William Wells) writes:
>	splsave = spltty();
>	while (!carrier_detect || already_opened) {
>		sleep(&line_flags, 29);
>	}
>	splx(splsave);
>... could someone clue me in on what is really happening?

Sleep() puts the current process to sleep, saving its state *including*
IPL.  A later wakeup() puts it back on the run queue, and when it is
subsequently resumed the IPL is restored to whatever its value was when
the code called sleep().  The carrier detect flag is thus set while the
process is sleeping.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris