Re: Random panics seen in 2.6.18-rc1

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

On Thu, 2006-07-13 at 06:51 -0700, Chandra Seetharaman wrote:

Tests are running for more than 2 hours now. So, this patch fixed the
panics i was seeing.

Thanks Ingo.

chandra
> 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);
> >  			}
-- 

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    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@us.ibm.com   |      .......you may get it.
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