linux-kernel - RE: [PATCH] slub: Proper kmemleak tracking if CONFIG_SLUB

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Message-ID: <0000014179e31953-a05dd7d1-d0f8-474f-810a-809cd8a724f8-000000@email.amazonses.com>
Date:	Wed, 2 Oct 2013 15:57:12 +0000
From:	Christoph Lameter <cl@...ux.com>
To:	"Bird, Tim" <Tim.Bird@...ymobile.com>
cc:	Frank Rowand <frowand.list@...il.com>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	"Bobniev, Roman" <Roman.Bobniev@...ymobile.com>,
	"Andersson, Björn" 
	<Bjorn.Andersson@...ymobile.com>
Subject: RE: [PATCH] slub: Proper kmemleak tracking if CONFIG_SLUB_DEBUG
 disabled

On Wed, 2 Oct 2013, Bird, Tim wrote:

> The problem child is actually the unconditional call to kmemleak_alloc()
> in kmalloc_large_node() (in slub.c).  The problem comes because that call
> is unconditional on CONFIG_SLUB_DEBUG but the kmemleak
> calls in the hook routines are conditional on CONFIG_SLUB_DEBUG.
> So if you have CONFIG_SLUB_DEBUG=n but CONFIG_DEBUG_KMEMLEAK=y,
> you get the false reports.

Right. You need to put the #ifdef CONFIG_SLUB_DEBUG around the hooks that
need it in the function itself instead of disabling the whole function if
CONFIG_SLUB_DEUBG is not set.

> Now, there are kmemleak calls in kmalloc_large_node() and kfree() that don't
> follow the "hook" pattern.  Should these be moved to 'hook' routines, to keep
> all the checks in the hooks?

That would be great.

> Personally, I like the idea of keeping bookeeping/tracing/debug stuff in hook
> routines.  I also like de-coupling CONFIG_SLUB_DEBUG and CONFIG_DEBUG_KMEMLEAK,
> but maybe others have a different opinon.  Unless someone speaks up, we'll
> move the the currently in-function kmemleak calls into hooks, and all of the
> kmemleak stuff out from under CONFIG_SLUB_DEBUG.
> We'll have to see if the ifdefs get a little messy.

Decouple of you want. CONFIG_SLUB_DEBUG may duplicate what you already do.

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