Date: Tue, 11 Oct 2005 09:35:26 +1300 From: Andrew Thompson <thompsa@freebsd.org> To: Brooks Davis <brooks@one-eyed-alien.net> Cc: Yar Tikhiy <yar@comp.chem.msu.su>, Pawel Jakub Dawidek <pjd@freebsd.org>, FreeBSD Current <current@freebsd.org> Subject: Re: panic: ifc_free_unit: bit is already cleared Message-ID: <20051010203526.GA1229@heff.fud.org.nz> In-Reply-To: <20051010202900.GA24213@odin.ac.hmc.edu> References: <20051005024903.GA72743@heff.fud.org.nz> <20051005203639.GA20552@garage.freebsd.pl> <20051005205515.GA30350@odin.ac.hmc.edu> <20051005210950.GB75848@heff.fud.org.nz> <20051009232849.GA27349@comp.chem.msu.su> <20051010022208.GA97249@heff.fud.org.nz> <20051010202900.GA24213@odin.ac.hmc.edu>
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On Mon, Oct 10, 2005 at 01:29:00PM -0700, Brooks Davis wrote:
> On Mon, Oct 10, 2005 at 03:22:08PM +1300, Andrew Thompson wrote:
> > On Mon, Oct 10, 2005 at 03:28:49AM +0400, Yar Tikhiy wrote:
> > > On Thu, Oct 06, 2005 at 10:09:50AM +1300, Andrew Thompson wrote:
> > >
> > > FWIW, I tried to look at the $subject problem since I had had it
> > > before, but just got a different panic:
> > >
> > > Memory modified after free 0xc140b000(4092) val=deadc0dc @ 0xc140b000
> > > panic: Most recently used by clone
> > >
> > > The clone code seems to have decremented something (refcount?) twice
> > > after freeing the memory chunk.
> >
> > I have been testing this patch and I think it fixes all the problems
> > discussed.
> >
> > It changes refcounting to count the number of cloned interfaces so
> > ifc_units is only freed when its safe. A new function has been added to
> > decrement this when a simple cloner module is unloaded. The cloner is
> > still detached first to prevent the race.
> >
> > In most cases the change is as simple as:
> > while ((sc = LIST_FIRST(&gre_softc_list)) != NULL) {
> > LIST_REMOVE(sc, sc_list);
> > mtx_unlock(&gre_mtx);
> > + ifc_simple_free(&gre_cloner, GRE2IFP(sc));
> > gre_destroy(sc);
> > mtx_lock(&gre_mtx);
> > }
>
> I don't see any reason why you can't just replace the specific destroy
> calls with calls to ifc_simple_destroy(). That would avoid expanding
> the API.
I did experiment with that. On some interfaces it would cause the global
mutex to be recursed, but that can be fixed. I'll have another go.
Andrew
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