cvs commit: src/sys/dev/fdc fdc.c fdcvar.h

[Nate Lawson]

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