linux-kernel - Re: [RFC 1/4] CONFIG

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Message-ID: <20070601180807.GB7968@redhat.com>
Date:	Fri, 1 Jun 2007 14:08:07 -0400
From:	Dave Jones <davej@...hat.com>
To:	Christoph Lameter <clameter@....com>
Cc:	young dave <hidave.darkstar@...il.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org
Subject: Re: [RFC 1/4] CONFIG_STABLE: Define it

On Wed, May 30, 2007 at 05:49:56PM -0700, Christoph Lameter wrote:
 > On Thu, 31 May 2007, young dave wrote:
 > 
 > > Hi Christoph,
 > > 
 > > > Introduce CONFIG_STABLE to control checks only useful for development.
 > > 
 > > What about control checks only as SLUB_DEBUG is set?
 > 
 > Debug code is always included in all builds unless it is an embedded 
 > system. Debug code is kept out of the hot path.
 > 
 > Disabling SLUB_DEBUG should only be done for embedded systems. That is why 
 > the option is in CONFIG_EMBEDDED.

Something I'd really love to have is a CONFIG option to decide if
slub_debug is set or not by default.  The reasoning behind this is that during
development of each Fedora release, I used to leave SLAB_DEBUG=y for
months on end and catch all kinds of nasties.

Now that I've switched it over to using slub, I ended up adding the
ugly patch below, because otherwise, no-one would ever run with
slub_debug and we'd miss out on all those lovely bugs.
(I have 'make release' and 'make debug' targets which enable/disable
 this [and other] patches in the Fedora kernel).

(Patch for illustration only, obviously not for applying).

Unless someone beats me to it, I'll hack up a CONFIG option around
this. Having that turned on if !CONFIG_STABLE would also be a win I think.

	Dave

--- linux-2.6/mm/slub.c~	2007-05-27 21:48:42.000000000 -0400
+++ linux-2.6/mm/slub.c	2007-05-27 21:51:22.000000000 -0400
@@ -323,7 +323,7 @@ static inline int slab_index(void *p, st
 /*
  * Debug settings:
  */
-static int slub_debug;
+static int slub_debug = DEBUG_DEFAULT_FLAGS;

 static char *slub_debug_slabs;

-- 
http://www.codemonkey.org.uk
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