Re: Random panics seen in 2.6.18-rc1

[Chandra Seetharaman <sekharan@us.ibm.com>]

On Thu, 2006-07-13 at 09:12 +0200, Ingo Molnar wrote:
> * Chandra Seetharaman <sekharan@us.ibm.com> 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@elte.hu>
> 
> 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@elte.hu>
> ---
>  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@us.ibm.com   |      .......you may get it.
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