Date: Thu, 23 Sep 2004 18:47:39 -0400 From: Brian Fundakowski Feldman <green@FreeBSD.org> To: John Baldwin <jhb@FreeBSD.org> Cc: Joerg Wunsch <joerg@FreeBSD.org> Subject: Re: cvs commit: src/sys/dev/fdc fdc.c fdcvar.h Message-ID: <20040923224739.GE959@green.homeunix.org> In-Reply-To: <200409231748.19685.jhb@FreeBSD.org> References: <200409232112.i8NLCLgQ065917@repoman.freebsd.org> <200409231748.19685.jhb@FreeBSD.org>
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On Thu, Sep 23, 2004 at 05:48:19PM -0400, John Baldwin wrote:
> On Thursday 23 September 2004 05:12 pm, Joerg Wunsch wrote:
> > joerg 2004-09-23 21:12:21 UTC
> >
> > FreeBSD src repository
> >
> > Modified files:
> > sys/dev/fdc fdc.c fdcvar.h
> > Log:
> > Implement terminating the worker thread when the driver is about to
> > be deregistered.
> >
> > Not yet tested, since by now, GEOM doesn't want us to deregister. PHK
> > wants to fix that RSN.
>
> Note that relying on a wakeup from your own code is not safe if you expect fdc
> to be a module since you could wakeup the thread doing the kldunload (and
> thus detach) and then be interrupted for an interrupt and it could unmap the
> memory backing that function before you get a chance to run again resulting
> in a panic. There is a special wakeup on the proc pointer in exit1() for
> kthreads to handle this case. I should likely move that into kthread_exit()
> however (which wouldn't be a functional change as far as you are concerned).
For example, in pff(4), ignoring the unrelated lines of code:
static void
pff_per_device_kthread(void *argp)
{
mtx_lock(&sc->sc_lock);
while (!sck->sck_exit) {
if (!sck->sck_update && !sck->sck_reset &&
STAILQ_EMPTY(&sck->sck_traps))
cv_wait(&sck->sck_needed, &sc->sc_lock);
}
mtx_unlock(&sc->sc_lock);
kthread_exit(0);
}
static void
pff_kill_kthread(struct pff_softc *sc)
{
if (sc->sc_flags & SC_KTHREAD) {
mtx_lock(&sc->sc_lock);
sc->sc_kthread.sck_exit = 1;
cv_signal(&sc->sc_kthread.sck_needed);
msleep(sc->sc_kthread.sck_proc, &sc->sc_lock, PPAUSE | PDROP,
"pffktc", 0);
}
}
--
Brian Fundakowski Feldman \'[ FreeBSD ]''''''''''\
<> green@FreeBSD.org \ The Power to Serve! \
Opinions expressed are my own. \,,,,,,,,,,,,,,,,,,,,,,\
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