linux-kernel - Warning at mm/slub.c

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Date:	Fri, 24 Jan 2014 11:52:37 -0200
From:	Fabio Estevam <festevam@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	penberg@...nel.org, Russell King <linux@....linux.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Warning at mm/slub.c

Peter,

Commit c65c1877bd68 (slub: use lockdep_assert_held) introduced the following
warning on mx5/mx6 systems (ARMv7) running linux-next 20140124:

Virtual kernel memory layout:
    vector  : 0xffff0000 - 0xffff1000   (   4 kB)
    fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
    vmalloc : 0xa0800000 - 0xff000000   (1512 MB)
    lowmem  : 0x80000000 - 0xa0000000   ( 512 MB)
    pkmap   : 0x7fe00000 - 0x80000000   (   2 MB)
    modules : 0x7f000000 - 0x7fe00000   (  14 MB)
      .text : 0x80008000 - 0x807e0edc   (8036 kB)
      .init : 0x807e1000 - 0x8082e300   ( 309 kB)
      .data : 0x80830000 - 0x8088b900   ( 367 kB)
       .bss : 0x8088b908 - 0x80debdb0   (5506 kB)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at mm/slub.c:1511 __kmem_cache_create+0x24c/0x318()
Modules linked in:
CPU: 0 PID: 0 Comm: swapper Not tainted 3.13.0-next-20140124 #685
Backtrace:
[<8001235c>] (dump_backtrace) from [<800124f8>] (show_stack+0x18/0x1c)
 r6:800da30c r5:00000009 r4:00000000 r3:00000000
[<800124e0>] (show_stack) from [<805e56d8>] (dump_stack+0x80/0x9c)
[<805e5658>] (dump_stack) from [<80027834>] (warn_slowpath_common+0x70/0x94)
 r4:00000000 r3:8083bcf0
[<800277c4>] (warn_slowpath_common) from [<8002787c>] (warn_slowpath_null+0x24/0
x2c)
 r8:80dbeb18 r7:00002000 r6:80821c94 r5:9ffd8000 r4:9f000000
[<80027858>] (warn_slowpath_null) from [<800da30c>] (__kmem_cache_create+0x24c/0
x318)
[<800da0c0>] (__kmem_cache_create) from [<80801d34>] (create_boot_cache+0x50/0x7
8)
 r10:9fffcb80 r9:412fc085 r8:80838880 r7:80821d08 r6:8073e360 r5:80821c94
 r4:0000002c
[<80801ce4>] (create_boot_cache) from [<80803544>] (kmem_cache_init+0x3c/0xe0)
 r6:80dbeb14 r5:80821c94 r4:80dc41a4 r3:00002000
[<80803508>] (kmem_cache_init) from [<807e19cc>] (start_kernel+0x198/0x384)
 r8:80838880 r7:8081f4c0 r6:ffffffff r5:8088b940 r4:00000001
[<807e1834>] (start_kernel) from [<90008074>] (0x90008074)
 r10:00000000 r8:90004059 r7:8083d3ac r6:8081f4bc r5:80838928 r4:10c53c7d
---[ end trace 3406ff24bd97382e ]---

If I revert this commit, the warning goes away.

It also goes away if this only line is removed:

diff --git a/mm/slub.c b/mm/slub.c
index d2388c8..fde5852 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1508,8 +1508,6 @@ static void discard_slab(struct kmem_cache *s,
struct page *page)
 static inline void add_partial(struct kmem_cache_node *n,
                 struct page *page, int tail)
 {
-    lockdep_assert_held(&n->list_lock);
-
     n->nr_partial++;
     if (tail == DEACTIVATE_TO_TAIL)
         list_add_tail(&page->lru, &n->partial);

Regards,

Fabio Estevam
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