Date: Tue, 22 Apr 1997 21:45:31 +0200 From: j@uriah.heep.sax.de (J Wunsch) To: hackers@freebsd.org Subject: Re: concurrent calls to device drivers Message-ID: <19970422214531.BX39690@uriah.heep.sax.de> In-Reply-To: <199704220425.NAA12940@genesis.atrad.adelaide.edu.au>; from Michael Smith on Apr 22, 1997 13:55:07 %2B0930 References: <199704210727.JAA15119@labinfo.iet.unipi.it> <199704220425.NAA12940@genesis.atrad.adelaide.edu.au>
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As Michael Smith wrote:
> That's ususally the best way to go; something like :
>
>
> sc_busy;
>
> ...
>
> fooread(...)
> {
> ...
>
> s = splfoo();
> while(sc->sc_busy) {
What's the splfoo() for?
Unless the interrupt service can modify sc_busy, you don't need to
protect it.
You gotta do a
obtain_mp_lock();
while(sc->sc_busy) {
...
}
release_mp_lock();
however. :-) On a uniprocessor however, only one process can be in
the kernel at a time.
--
cheers, J"org
joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)
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