Re: panic: ifc_free_unit: bit is already cleared

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 _at_ 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