On Wed, 08 Nov 2006 12:42:17 -0500
Jeff Layton <[email protected]> wrote:
> On Mon, 2006-06-19 at 06:31 -0400, Chuck Ebbert wrote:
> > Looking at this code:
> >
> > const struct exception_table_entry *search_exception_tables(unsigned long addr)
> > {
> > const struct exception_table_entry *e;
> >
> > e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
> > if (!e)
> > e = search_module_extables(addr);
> > return e;
> > }
> >
> > const struct exception_table_entry *search_module_extables(unsigned long addr)
> > {
> > unsigned long flags;
> > const struct exception_table_entry *e = NULL;
> > struct module *mod;
> >
> > spin_lock_irqsave(&modlist_lock, flags);
> > list_for_each_entry(mod, &modules, list) {
> > if (mod->num_exentries == 0)
> > continue;
> >
> > e = search_extable(mod->extable,
> > mod->extable + mod->num_exentries - 1,
> > addr);
> > if (e)
> > break;
> > }
> > spin_unlock_irqrestore(&modlist_lock, flags);
> >
> > /* Now, if we found one, we are running inside it now, hence
> > we cannot unload the module, hence no refcnt needed. */
> > return e;
> > }
> >
> >
> > search_module_extables() takes a spinlock. If some kind of fault occurs
> > while it's holding that lock (module list corrupted etc.,) won't it be
> > re-entered while looking for its own fault handler? If so, would this
> > be a possible fix?
> >
> > const struct exception_table_entry *search_exception_tables(unsigned long addr)
> > {
> > const struct exception_table_entry *e;
> >
> > if (core_kernel_text(addr))
> > e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
> > else
> > e = search_module_extables(addr);
> >
> > return e;
> > }
>
> I seem to be able to reliably trigger this spinlock recursion problem
> with systemtap on a RHEL4 kernel. The patch suggested above does seem to
> correct it, but I'm not familiar enough with extables to know whether
> the approach here is correct.
>
It'll still deadlock if we take an oops from a module, won't it?
The usual way of fixing this sort of thing is to play games with
oops_in_progress.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
