Date: Mon, 23 Jul 2007 15:42:14 -0400 From: John Baldwin <jhb@freebsd.org> To: Nate Lawson <nate@root.org> Cc: cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org, Andrew Thompson <thompsa@freebsd.org> Subject: Re: cvs commit: src/sys/compat/ndis subr_ntoskrnl.c Message-ID: <200707231542.14803.jhb@freebsd.org> In-Reply-To: <46A4FF7B.5000501@root.org> References: <200707222053.l6MKrS6v040649@repoman.freebsd.org> <200707231050.51004.jhb@freebsd.org> <46A4FF7B.5000501@root.org>
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On Monday 23 July 2007 03:20:27 pm Nate Lawson wrote:
> John Baldwin wrote:
> > On Sunday 22 July 2007 04:53:28 pm Andrew Thompson wrote:
> >> thompsa 2007-07-22 20:53:28 UTC
> >>
> >> FreeBSD src repository
> >>
> >> Modified files:
> >> sys/compat/ndis subr_ntoskrnl.c
> >> Log:
> >> ndis will signal the kthread to exit and then sleep on the proc pointer
to
> >> be woken up by kthread_exit. This is racey and in some cases the
kthread
> > will
> >> exit before ndis gets around to sleep so it will be stuck indefinitely.
> > This
> >> change reuses the kq_exit variable to indicate that the thread has gone
> > and
> >> will loop on tsleep with a timeout waiting for it. If the kthread has
> > already
> >> exited then it will not sleep at all.
> >
> > As long as you use a lock you are ok. That is:
> >
> > foo_detach()
> > {
> >
> > mtx_lock(&lock);
> > please_die = 1;
> > msleep(&proc, &lock, ..., 0);
> > mtx_unlock(&lock);
> > }
> >
> > foo_main()
> > {
> >
> > mtx_lock(&lock);
> > while (!please_die) {
> > do_stuff();
> > }
> > mtx_unlock(&lock);
> > kthread_exit(0);
> > }
> >
> > works fine.
>
> How can foo_detach() acquire the lock to set "please_die" if foo_main()
> always holds it? Are you assuming that "do_stuff()" drops the lock
> somewhere internally?
Yes, normally you do an msleep() to wait for work.
--
John Baldwin
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