Messages in this thread | | | Subject | Re: [PATCH 05/15] kmemleak: Add the slub memory allocation/freeing hooks | From | Catalin Marinas <> | Date | Fri, 12 Dec 2008 13:45:43 +0000 |
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On Thu, 2008-12-11 at 23:30 +0200, Pekka Enberg wrote: > Catalin Marinas wrote: > > This patch adds the callbacks to memleak_(alloc|free) functions from the > > slub allocator. > > > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > > Cc: Christoph Lameter <cl@linux-foundation.org> > > Cc: Pekka Enberg <penberg@cs.helsinki.fi> > > Hmm, I'm not sure I understand why struct kmem_cache_cpu ->freelist is > never scanned.
Did you get any false positives? Or were you expecting false negatives because of freelist scanning which never occurred?
> For SMP, I suppose kmemleak doesn't scan the per-CPU > areas?
It should scan the per-CPU areas in the memleak_scan() function:
#ifdef CONFIG_SMP /* per-cpu sections scanning */ for_each_possible_cpu(i) scan_block(__per_cpu_start + per_cpu_offset(i), __per_cpu_end + per_cpu_offset(i), NULL); #endif
> But for UP, struct kmem_cache is allocated with kmalloc() and > that contains struct kmem_cache_cpu as well.
They should be scanned as well.
> And I suppose we never scan struct pages either. Otherwise ->freelist > there would be a problem as well.
It was scanning the mem_map arrays in the past but removed this part and haven't seen any problems (on ARM).
Why would the ->freelist be a problem? I don't fully understand the slub allocator. Aren't objects added to the freelist only after they were freed? In __slab_alloc there seems to be a line:
c->page->freelist = NULL;
so the freelist won't count as a reference anymore. After freeing an object, kmemleak no longer cares about references to it.
-- Catalin
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