linux-kernel - Re: [bug] SLUB + mm/slab.c boot crash in -rc9

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Message-ID: <20080415062534.GA9172@elte.hu>
Date:	Tue, 15 Apr 2008 08:25:34 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	linux-kernel@...r.kernel.org, Christoph Lameter <clameter@....com>,
	Mel Gorman <mel@....ul.ie>, Nick Piggin <npiggin@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Yinghai.Lu@....com
Subject: Re: [bug] SLUB + mm/slab.c boot crash in -rc9


you asked me to run with the debug patch attached below. I just tried 
vanilla -rc9 (head 120dd64cacd4fb7) and it still crashes with this 
config:

  http://redhat.com/~mingo/misc/config-Thu_Apr_10_10_41_16_CEST_2008.bad.rc9

debug output is:

  http://redhat.com/~mingo/misc/log-Thu_Apr_10_10_41_16_CEST_2008.bad.rc9

so it's probably the first few page allocations (setup_cpu_cache()) 
going wrong already - suggesting a some fundamental borkage in SLAB?

note, when i change SLAB to SLUB (and keep the config unchanged 
otherwise), i get a similar early crash:

  http://redhat.com/~mingo/misc/log-Tue_Apr_15_07_24_59_CEST_2008.bad
  http://redhat.com/~mingo/misc/config-Tue_Apr_15_07_24_59_CEST_2008.bad

i've also uploaded a bzImage (SLUB, debug patch not applied) that you 
can pick up and run on any 32-bit test-system:

  http://redhat.com/~mingo/misc/bzImage-Thu_Apr_10_10_41_16_CEST_2008.bad.rc9

it's a relatively generic bzImage that should boot on most whitebox PCs 
on most distros as long as you use a pure ext3 setup and might even give 
you networking (no modules or initrd is needed). It boots fine on two 
other 32-bit PCs i have (an Intel laptop and an AMD desktop).

	Ingo

Index: linux/mm/page_alloc.c
===================================================================
--- linux.orig/mm/page_alloc.c
+++ linux/mm/page_alloc.c
@@ -1485,6 +1485,7 @@ restart:
 		 * Happens if we have an empty zonelist as a result of
 		 * GFP_THISNODE being used on a memoryless node
 		 */
+		WARN_ON(1);
 		return NULL;
 	}
 
Index: linux/mm/slab.c
===================================================================
--- linux.orig/mm/slab.c
+++ linux/mm/slab.c
@@ -1682,6 +1682,7 @@ static void *kmem_getpages(struct kmem_c
 		flags |= __GFP_RECLAIMABLE;
 
 	page = alloc_pages_node(nodeid, flags, cachep->gfporder);
+	WARN_ON(!page);
 	if (!page)
 		return NULL;
 
@@ -2620,6 +2621,7 @@ static struct slab *alloc_slabmgmt(struc
 		/* Slab management obj is off-slab. */
 		slabp = kmem_cache_alloc_node(cachep->slabp_cache,
 					      local_flags & ~GFP_THISNODE, nodeid);
+		WARN_ON(!slabp);
 		if (!slabp)
 			return NULL;
 	} else {
--
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