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Date: Sat, 26 Mar 2011 18:45:07 +0100
From: Eric Dumazet <eric.dumazet@...il.com>
To: Ingo Molnar <mingo@...e.hu>
Cc: Pekka Enberg <penberg@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Christoph Lameter <cl@...ux.com>,
torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
tj@...nel.org, npiggin@...nel.dk, rientjes@...gle.com,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] slub: Disable the lockless allocator
Le samedi 26 mars 2011 à 12:47 +0100, Ingo Molnar a écrit :
> The commit below solves this crash for me. Could we please apply this simple
> patch, until the real bug has been found, to keep upstream debuggable? The
> eventual fix can then re-enable the lockless allocator.
>
> Thanks,
>
> Ingo
>
> --------------->
> From bb764182707216faeb815c3bbdf6a9e9992a459a Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <mingo@...e.hu>
> Date: Sat, 26 Mar 2011 12:40:30 +0100
> Subject: [PATCH] slub: Disable the lockless allocator
>
> This boot crash:
>
> Inode-cache hash table entries: 65536 (order: 7, 524288 bytes)
> Memory: 1011352k/1048512k available (11595k kernel code, 452k absent, 36708k reserved, 6343k data, 1024k init)
> BUG: unable to handle kernel paging request at ffff87ffc1fdd020
> IP: [<ffffffff812b50c2>] this_cpu_cmpxchg16b_emu+0x2/0x1c
> PGD 0
> Oops: 0000 [#1]
> last sysfs file:
> CPU 0
> Pid: 0, comm: swapper Not tainted 2.6.38-08569-g16c29da #110593 System manufacturer System Product Name/A8N-E
> RIP: 0010:[<ffffffff812b50c2>] [<ffffffff812b50c2>] this_cpu_cmpxchg16b_emu+0x2/0x1c
> RSP: 0000:ffffffff82003e78 EFLAGS: 00010086
> RAX: ffff88003f8020c0 RBX: ffff88003f802180 RCX: 0000000000000002
> RDX: 0000000000000001 RSI: ffff88003ffc2020 RDI: ffffffff8219be43
Interesting. I am wondering if its not a per_cpu problem, or another
problem uncovered by lockless allocator ?
Old values of cmpxchg16b() :
RAX = ffff88003f8020c0 , RDX = 1
New values
RBX = ffff88003f802180 , RCX = 2
address : RSI = ffff88003ffc2020
RSI is supposed to be a dynamic percpu addr
Yet this value seems pretty outside of pcpu pools
CR2: ffff87ffc1fdd020
On my machine, if I add this patch to display cpu_slab values :
diff --git a/mm/slub.c b/mm/slub.c
index f881874..3b118f3 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2364,7 +2364,7 @@ static inline int alloc_kmem_cache_cpus(struct kmem_cache *s)
/* Regular alignment is sufficient */
s->cpu_slab = alloc_percpu(struct kmem_cache_cpu);
#endif
-
+ pr_err("cpu_slab=%p\n", s->cpu_slab);
if (!s->cpu_slab)
return 0;
I get following traces :
First ones are allocated from the static pcpu area (zero based)
Looks consistent with :
00000000000127c0 D __per_cpu_end
[ 0.000000] cpu_slab=00000000000147c0
[ 0.000000] cpu_slab=00000000000147e0
[ 0.000000] cpu_slab=0000000000014800
[ 0.000000] cpu_slab=0000000000014820
[ 0.000000] cpu_slab=0000000000014840
[ 0.000000] cpu_slab=0000000000014860
[ 0.000000] cpu_slab=0000000000014880
[ 0.000000] cpu_slab=00000000000148a0
[ 0.000000] cpu_slab=00000000000148c0
[ 0.000000] cpu_slab=00000000000148e0
[ 0.000000] cpu_slab=0000000000014900
[ 0.000000] cpu_slab=0000000000014920
[ 0.000000] cpu_slab=0000000000014940
[ 0.000000] cpu_slab=0000000000014960
[ 0.000000] cpu_slab=0000000000014980
[ 0.000000] cpu_slab=00000000000149a0
[ 0.000000] cpu_slab=00000000000149c0
[ 0.000000] cpu_slab=00000000000149e0
[ 0.000000] cpu_slab=0000000000014a00
[ 0.000000] cpu_slab=0000000000014a20
[ 0.000000] cpu_slab=0000000000014a40
[ 0.000000] cpu_slab=0000000000014a60
[ 0.000000] cpu_slab=0000000000014a80
[ 0.000000] cpu_slab=0000000000014aa0
[ 0.000000] cpu_slab=0000000000014ac0
[ 0.000000] cpu_slab=0000000000014ae0
[ 0.000000] cpu_slab=0000000000014b00
[ 0.000000] cpu_slab=0000000000014b20
[ 0.000000] cpu_slab=0000000000014b40
[ 0.000000] cpu_slab=0000000000014c80
[ 0.000000] cpu_slab=0000000000017240
[ 0.000000] cpu_slab=0000000000017260
[ 0.000350] cpu_slab=0000000000017280
[ 0.000461] cpu_slab=00000000000172a0
[ 0.000573] cpu_slab=00000000000172c0
[ 0.000684] cpu_slab=00000000000172e0
[ 0.000797] cpu_slab=0000000000017300
[ 0.000918] cpu_slab=0000000000017320
[ 0.001031] cpu_slab=0000000000017340
[ 0.001141] cpu_slab=0000000000017360
[ 0.001253] cpu_slab=0000000000017380
[ 0.001365] cpu_slab=00000000000173a0
[ 0.001477] cpu_slab=00000000000173c0
[ 0.001589] cpu_slab=00000000000173e0
[ 0.001713] cpu_slab=0000000000017400
[ 0.001833] cpu_slab=0000000000017420
[ 0.001946] cpu_slab=0000000000017440
[ 0.002057] cpu_slab=0000000000017460
[ 0.003548] cpu_slab=0000000000017480
[ 0.004380] cpu_slab=00000000000174a0
[ 0.004508] cpu_slab=00000000000174d0
[ 0.004727] cpu_slab=00000000000174f0
[ 0.005006] cpu_slab=0000000000017550
[ 0.005187] cpu_slab=0000000000017590
[ 0.005345] cpu_slab=00000000000175c0
[ 0.007824] cpu_slab=0000000000017600
[ 0.007935] cpu_slab=0000000000017620
[ 0.008048] cpu_slab=0000000000017640
[ 0.008159] cpu_slab=0000000000017660
[ 0.008271] cpu_slab=0000000000017680
[ 1.496852] cpu_slab=00000000000177b0
[ 1.497347] cpu_slab=0000000000017870
[ 1.497509] cpu_slab=0000000000017890
[ 1.497632] cpu_slab=00000000000178b0
[ 1.497749] cpu_slab=00000000000178d0
[ 1.497868] cpu_slab=0000000000017970
[ 1.510931] cpu_slab=0000000000017a70
[ 1.511000] cpu_slab=0000000000017a90
[ 1.511068] cpu_slab=0000000000017ab0
[ 1.511139] cpu_slab=0000000000017ad0
[ 1.511208] cpu_slab=0000000000017c70
[ 1.511430] cpu_slab=0000000000017c90
[ 1.511543] cpu_slab=0000000000017cb0
[ 1.511659] cpu_slab=0000000000017cd0
[ 1.511816] cpu_slab=0000000000017d70
[ 1.511929] cpu_slab=0000000000017d90
[ 1.538272] cpu_slab=0000000000017db0
[ 1.538384] cpu_slab=0000000000017dd0
[ 1.538500] cpu_slab=0000000000017e70
[ 1.538615] cpu_slab=0000000000017e90
[ 1.538731] cpu_slab=0000000000017eb0
[ 1.538851] cpu_slab=0000000000017ed0
[ 1.555795] cpu_slab=0000000000017f70
[ 1.555908] cpu_slab=0000000000017f90
[ 1.578009] cpu_slab=0000000000017fc0
[ 1.578122] cpu_slab=0000000000017fe0
[ 1.578240] cpu_slab=0000000000018070
[ 1.578352] cpu_slab=0000000000018090
[ 1.578466] cpu_slab=00000000000180b0
[ 1.578685] cpu_slab=00000000000180d0
[ 1.578843] cpu_slab=00000000000181d0
[ 1.579371] cpu_slab=0000000000018270
[ 1.579453] cpu_slab=0000000000018290
[ 1.579531] cpu_slab=00000000000182b0
[ 1.579636] cpu_slab=00000000000182d0
[ 1.580122] cpu_slab=0000000000019370
[ 1.580202] cpu_slab=0000000000019390
[ 1.580482] cpu_slab=0000000000019e20
[ 1.606265] cpu_slab=0000000000019e40
[ 1.606337] cpu_slab=0000000000019e60
[ 1.606405] cpu_slab=0000000000019e80
[ 1.633467] cpu_slab=0000000000019ea0
[ 1.633622] cpu_slab=0000000000019ec0
[ 1.633753] cpu_slab=0000000000019ee0
[ 1.633881] cpu_slab=0000000000019f00
[ 1.634013] cpu_slab=0000000000019f20
[ 1.634139] cpu_slab=0000000000019f40
[ 1.634294] cpu_slab=0000000000019f60
[ 1.634582] cpu_slab=0000000000019f80
[ 1.634918] cpu_slab=0000000000019fc0
[ 1.635051] cpu_slab=0000000000019fe0
After exhaustion of static pcpu area we switch do vmalloc() based ones :
[ 1.635175] cpu_slab=000060fee0002070
[ 1.635324] cpu_slab=000060fee0002090
[ 1.635445] cpu_slab=000060fee00020b0
[ 1.635563] cpu_slab=000060fee00020d0
[ 1.635690] cpu_slab=000060fee00020f0
[ 1.635802] cpu_slab=000060fee0002110
[ 1.635951] cpu_slab=000060fee0002140
[ 1.636081] cpu_slab=000060fee0002170
[ 1.636309] cpu_slab=000060fee0002190
[ 1.636882] cpu_slab=000060fee00021d0
[ 1.637257] cpu_slab=000060fee0002270
[ 1.637381] cpu_slab=000060fee0002290
[ 3.264327] cpu_slab=000060fee0002860
[ 3.264465] cpu_slab=000060fee0002880
[ 3.267217] cpu_slab=000060fee0002900
[ 3.294910] cpu_slab=000060fee0002950
[ 3.302653] cpu_slab=000060fee0002bb0
[ 3.302783] cpu_slab=000060fee0002bd0
[ 3.302899] cpu_slab=000060fee0002bf0
[ 3.303033] cpu_slab=000060fee0002c10
[ 3.303153] cpu_slab=000060fee0002c30
[ 3.303268] cpu_slab=000060fee0002c50
[ 3.303539] cpu_slab=000060fee0004f90
[ 3.303675] cpu_slab=000060fee0004fb0
[ 3.303811] cpu_slab=000060fee0005030
[ 3.303939] cpu_slab=000060fee0005050
# grep pcpu_get_vm_areas /proc/vmallocinfo
0xffffe8ff5fc00000-0xffffe8ff5fe00000 2097152 pcpu_get_vm_areas+0x0/0x580 vmalloc
0xffffe8ffffc00000-0xffffe8ffffe00000 2097152 pcpu_get_vm_areas+0x0/0x580 vmalloc
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