Re: Random panics seen in 2.6.18-rc1

From: Chandra Seetharaman
Date: Thu Jul 13 2006 - 09:49:24 EST


On Thu, 2006-07-13 at 09:12 +0200, Ingo Molnar wrote:
> * Chandra Seetharaman <sekharan@xxxxxxxxxx> wrote:
>
> > By adding one patch at a time to 2.6.17's mm/slab.c, I found that the
> > following patch is the cause of the panic.
> > --------------
> > [PATCH] lockdep: annotate SLAB code
>
> great debugging!

Thanks.
>
> I have reviewed that patch, and there's only one chunk that could
> possibly have a functional effect. The patch below undoes it - does that
> fix the crashes you are seeing? [If you have lockdep enabled then this
> patch will cause a lockdep false positive - ignore that one for now, it
> shouldnt impact the crash scenario itself.]
>

started the tests with this patch now. will report back in couple of
hours... earlier if it crashes again :), which i doubt.

Thanks & regards,

chandra
> Ingo
>
> --------------------->
> Subject: revert slab.c locking change
> From: Ingo Molnar <mingo@xxxxxxx>
>
> Chandra Seetharaman reported SLAB crashes caused by the slab.c
> lock annotation patch. There is only one chunk of that patch
> that has a material effect on the slab logic - this patch
> undoes that chunk.
>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
> ---
> mm/slab.c | 9 ---------
> 1 file changed, 9 deletions(-)
>
> Index: linux/mm/slab.c
> ===================================================================
> --- linux.orig/mm/slab.c
> +++ linux/mm/slab.c
> @@ -3100,16 +3100,7 @@ static void free_block(struct kmem_cache
> if (slabp->inuse == 0) {
> if (l3->free_objects > l3->free_limit) {
> l3->free_objects -= cachep->num;
> - /*
> - * It is safe to drop the lock. The slab is
> - * no longer linked to the cache. cachep
> - * cannot disappear - we are using it and
> - * all destruction of caches must be
> - * serialized properly by the user.
> - */
> - spin_unlock(&l3->list_lock);
> slab_destroy(cachep, slabp);
> - spin_lock(&l3->list_lock);
> } else {
> list_add(&slabp->list, &l3->slabs_free);
> }
--

----------------------------------------------------------------------
Chandra Seetharaman | Be careful what you choose....
- sekharan@xxxxxxxxxx | .......you may get it.
----------------------------------------------------------------------


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/