Date: Sun, 10 Nov 2002 23:34:36 -0500 From: Jake Burkholder <jake@locore.ca> To: Matthew Jacob <mjacob@feral.com> Cc: "Alan L. Cox" <alc@imimic.com>, jeff@freebsd.org, cvs-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/vm uma_dbg.c Message-ID: <20021110233436.C85338@locore.ca> In-Reply-To: <Pine.BSF.4.21.0211101820030.62965-100000@beppo>; from mjacob@feral.com on Sun, Nov 10, 2002 at 06:24:42PM -0800 References: <Pine.BSF.4.21.0211101810230.62965-100000@beppo> <Pine.BSF.4.21.0211101820030.62965-100000@beppo>
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Apparently, On Sun, Nov 10, 2002 at 06:24:42PM -0800,
Matthew Jacob said words to the effect of;
>
>
> > >
> > > Matt, can you try acquiring and releasing the zone mutex in
> > > uma_dbg_alloc() and uma_dbg_free() instead?
> > >
> >
> > Sure- let me look at this a little closer - I'll interrupt the make
> > release and try a different approach.
>
> The trouble is that slab_zalloc sets value in us_freelist with the zone
> lock not held.
>
> THe locking for falling uma_dbg_alloc and uma_dbg_free doesn't seem all
> that consistent to me.
>
> It's getting beyond my easy reading/fixing. If there is no MI atomic
> set/clear 8 (which, IMO, is kind of a bug), I'd just change us_freelist
> to be an int for now. This change seemed to make a difference- but it
> could be coincidence.
>
This would be my suggestion:
Index: sys/vm/uma_core.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/uma_core.c,v
retrieving revision 1.41
diff -u -r1.41 uma_core.c
--- sys/vm/uma_core.c 1 Nov 2002 01:01:27 -0000 1.41
+++ sys/vm/uma_core.c 11 Nov 2002 04:11:38 -0000
@@ -1348,7 +1348,9 @@
("uma_zalloc: Bucket pointer mangled."));
cache->uc_allocs++;
#ifdef INVARIANTS
+ ZONE_LOCK(zone);
uma_dbg_alloc(zone, NULL, item);
+ ZONE_UNLOCK(zone);
#endif
CPU_UNLOCK(zone, cpu);
if (zone->uz_ctor)
@@ -1698,10 +1700,12 @@
("uma_zfree: Freeing to non free bucket index."));
bucket->ub_bucket[bucket->ub_ptr] = item;
#ifdef INVARIANTS
+ ZONE_LOCK(zone);
if (zone->uz_flags & UMA_ZFLAG_MALLOC)
uma_dbg_free(zone, udata, item);
else
uma_dbg_free(zone, NULL, item);
+ ZONE_UNLOCK(zone);
#endif
CPU_UNLOCK(zone, cpu);
return;
uma_dbg_* are called with the zone lock held everywhere else, and the
us_freelist is used with the zone lock held everywhere else as well.
slab_zalloc is working on a newly created slab that doesn't have any
other references, so it doesn't need to be locked until its added to
the zone.
Jake
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