Re: panic: uma_zone_slab is looping

On Mon, Dec 20, 2004 at 06:41:04PM -0500, Bosko Milekic wrote:
> 
>   I realize it's been a while.
> 
>   Anyway, what I *think* is going on here is that slab_zalloc() is
>   actually returning NULL even when called with M_WAITOK.  Further
>   inspection in slab_zalloc() reveals that this could come from several
>   places.  One of them is kmem_malloc() itself, which I doubt will ever
>   return NULL if called with M_WAITOK.  If this assumption is indeed
>   correct, then the NULL must be being returned by slab_zalloc() itself,
>   or due to a failed uma_zalloc_internal() call.  It is also possible
>   that slab_zalloc() returns NULL if the init that gets called for the
>   zone fails.  However, judging from the stack trace you provided, the
>   init in question is mb_init_pack() (kern_mbuf.c).  This particular
>   init DOES perform an allocation and CAN in theory fail, but I believe
>   it should be called with M_WAITOK as well, and so it should also never
>   fail in theory.
> 
>   Have you gotten any further with the analysis of this particular
>   trace?  If not, I would suggest adding some more printf()s and
>   analysis into slab_zalloc() itself, to see if that is indeed what is
>   causing the infinite looping in uma_zone_slab() and, if so, attempt to
>   figure out what part of slab_zalloc() is returning the NULL.

OK, did that: http://www.holm.cc/stress/log/freeze03.html

> 
>   Happy Holidays,
>  -Bosko
> 
> On Thu, Dec 09, 2004 at 03:42:33PM +0100, Peter Holm wrote:
> > I modified:
> > 
> > $ cvs diff -u uma_core.c 
> > Index: uma_core.c
> > ===================================================================
> > RCS file: /home/ncvs/src/sys/vm/uma_core.c,v
> > retrieving revision 1.110
> > diff -u -r1.110 uma_core.c
> > --- uma_core.c  6 Nov 2004 11:43:30 -0000       1.110
> > +++ uma_core.c  9 Dec 2004 14:38:32 -0000
> > _at__at_ -1926,6 +1926,7 _at__at_
> >  {
> >         uma_slab_t slab;
> >         uma_keg_t keg;
> > +       int i;
> >  
> >         keg = zone->uz_keg;
> >  
> > _at__at_ -1943,7 +1944,8 _at__at_
> >  
> >         slab = NULL;
> >  
> > -       for (;;) {
> > +       for (i = 0;;i++) {
> > +               KASSERT(i < 10000, ("uma_zone_slab is looping"));
> >                 /*
> >                  * Find a slab with some space.  Prefer slabs that are partially
> >                  * used over those that are totally full.  This helps to reduce
> > 
> > 
> > and caught this one:
> > http://www.holm.cc/stress/log/cons94.html
> > -- 
> > Peter Holm
> > _______________________________________________
> > freebsd-current_at_freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-current
> > To unsubscribe, send any mail to "freebsd-current-unsubscribe_at_freebsd.org"
> 
> -- 
> Bosko Milekic
> bmilekic_at_technokratis.com
> bmilekic_at_FreeBSD.org

-- 
Peter Holm