Date: Thu, 23 Sep 2004 16:19:34 -0700 From: Nate Lawson <nate@root.org> To: Brian Fundakowski Feldman <green@FreeBSD.org> Cc: Joerg Wunsch <joerg@FreeBSD.org> Subject: Re: cvs commit: src/sys/dev/fdc fdc.c fdcvar.h Message-ID: <41535A06.7090809@root.org> In-Reply-To: <20040923224739.GE959@green.homeunix.org> References: <200409232112.i8NLCLgQ065917@repoman.freebsd.org> <200409231748.19685.jhb@FreeBSD.org> <20040923224739.GE959@green.homeunix.org>
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Brian Fundakowski Feldman wrote: > 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); > } > } > Or simpler: foo_kill(): error = kthread_suspend(p, kproc_shutdown_wait * hz); if (error == EWOULDBLOCK) printf("timed out\n"); foo_thread(): for (;;) { mtx_unlock(&bdlock); kthread_suspend_check(bufdaemonproc); ... mtx_lock(&bdlock); if (numdirtybuffers <= lodirtybuffers) msleep(&bd_request, &bdlock, PVM, "psleep", hz); -- Nate
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