Re: BUG in 3.19.0-rc3+

From: Konstantin Khlebnikov
Date: Sun Jan 11 2015 - 04:38:06 EST

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On Sun, Jan 11, 2015 at 11:16 AM, Chris Clayton
<chris2553@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> I've done the bisect and the outcome is below, but, because I almost always forget to mention it, I'll say here that I
> am running a 32 bit user space on a 64 bit kernel.
>
> On 01/10/15 20:17, Chris Clayton wrote:
>> Hi,
>>
>> I'm getting a bug a BUG report from a kernel built from a pull (earlier today) of the current development kernel
>> (running git describe gives v3.19-rc3-169-geb74926). So that I have useable wireless networking, I have also applied the
>> latest seven iwlwifi patches from the wireless-drivers git tree. Prior to today's pull, I was not seeing anything
>> unusual in dmesg.
>>
>> The BUG reported is as follows:
>>
>> Jan 10 19:41:32 laptop kernel: ------------[ cut here ]------------
>> Jan 10 19:41:32 laptop kernel: kernel BUG at mm/rmap.c:399!
>> Jan 10 19:41:32 laptop kernel: invalid opcode: 0000 [#1] PREEMPT SMP
>> Jan 10 19:41:32 laptop kernel: Modules linked in: rfcomm snd_hda_codec_via iwlmvm coretemp snd_hda_codec_hdmi
>> snd_hda_codec_generic snd_hda_intel mac80211 hwmon snd_hda_controller x86_pkg_temp_thermal acpi_cpufreq iwlwifi cfg80211
>> snd_hda_codec snd_hwdep
>> Jan 10 19:41:32 laptop kernel: CPU: 1 PID: 353 Comm: fc-cache Not tainted 3.19.0-rc3+ #42
>> Jan 10 19:41:32 laptop kernel: Hardware name: Notebook W65_67SZ /W65_67SZ
>> , BIOS 1.03.05 02/26/2014
>> Jan 10 19:41:32 laptop kernel: task: ffff8800da98c5c0 ti: ffff880408dd4000 task.ti: ffff880408dd4000
>> Jan 10 19:41:32 laptop kernel: RIP: 0010:[<ffffffff810ef7ea>] [<ffffffff810ef7ea>] unlink_anon_vmas+0x17a/0x200
>> Jan 10 19:41:33 laptop kernel: RSP: 0018:ffff880408dd7d88 EFLAGS: 00010286
>> Jan 10 19:41:33 laptop kernel: RAX: ffff88040b79e150 RBX: ffff88040b79e140 RCX: 00000000ffffffff
>> Jan 10 19:41:33 laptop kernel: RDX: ffffffff00000001 RSI: ffff880409f04360 RDI: ffff880409f04320
>> Jan 10 19:41:33 laptop kernel: RBP: ffff88040cb13278 R08: 0000000000000000 R09: ffff88040d801c00
>> Jan 10 19:41:33 laptop kernel: R10: ffff88041fa546e0 R11: ffff88040b79e160 R12: ffff880409f04320
>> Jan 10 19:41:33 laptop kernel: R13: ffff88040cb13278 R14: ffff88040cb13288 R15: ffff88040cb13210
>> Jan 10 19:41:33 laptop kernel: FS: 0000000000000000(0000) GS:ffff88041fa40000(0000) knlGS:0000000000000000
>> Jan 10 19:41:33 laptop kernel: CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
>> Jan 10 19:41:33 laptop kernel: CR2: 00000000f722c8d4 CR3: 00000004082a8000 CR4: 00000000001407e0
>> Jan 10 19:41:33 laptop kernel: Stack:
>> Jan 10 19:41:33 laptop kernel: ffff88040d6cfbd8 ffff88040d6cfba0 ffff88040cecd160 ffff88040cb13210
>> Jan 10 19:41:33 laptop kernel: ffff88040cbbb630 00000000f7151000 ffff880408dd7e28 0000000000000000
>> Jan 10 19:41:33 laptop kernel: 0000000000000000 ffffffff810e3633 0000000000000000 0000000000000000
>> Jan 10 19:41:33 laptop kernel: Call Trace:
>> Jan 10 19:41:33 laptop kernel: [<ffffffff810e3633>] ? free_pgtables+0x83/0xf0
>> Jan 10 19:41:34 laptop kernel: [<ffffffff810ec3c3>] ? exit_mmap+0xc3/0x150
>> Jan 10 19:41:34 laptop kernel: [<ffffffff8103980d>] ? __do_page_fault+0x17d/0x4b0
>> Jan 10 19:41:34 laptop kernel: [<ffffffff81042a21>] ? mmput+0x21/0xc0
>> Jan 10 19:41:34 laptop kernel: [<ffffffff8104673d>] ? do_exit+0x26d/0xa50
>> Jan 10 19:41:34 laptop kernel: [<ffffffff8111fe89>] ? mntput_no_expire+0x9/0x140
>> Jan 10 19:41:34 laptop kernel: [<ffffffff8105ca1c>] ? task_work_run+0xbc/0xf0
>> Jan 10 19:41:34 laptop kernel: [<ffffffff81047d44>] ? do_group_exit+0x34/0xb0
>> Jan 10 19:41:34 laptop kernel: [<ffffffff81047dcf>] ? SyS_exit_group+0xf/0x10
>> Jan 10 19:41:34 laptop kernel: [<ffffffff815e0f9f>] ? sysenter_dispatch+0x7/0x1e
>> Jan 10 19:41:34 laptop kernel: Code: 00 ad de 48 89 43 18 e8 c5 f9 00 00 48 8b 45 10 48 8d 55 10 48 83 e8 10 49 39 d6 74
>> 54 48 8b 7d 08 48 89 eb 8b 57 34 85 d2 74 9e <0f> 0b 0f 1f 40 00 e8 6b fc ff ff eb 9a 66 0f 1f 84 00 00 00 00
>> Jan 10 19:41:34 laptop kernel: RIP [<ffffffff810ef7ea>] unlink_anon_vmas+0x17a/0x200
>> Jan 10 19:41:34 laptop kernel: RSP <ffff880408dd7d88>
>> Jan 10 19:41:34 laptop kernel: ---[ end trace 4aa713b2a9aa664b ]---
>> Jan 10 19:41:34 laptop kernel: Fixing recursive fault but reboot is needed!
>> Jan 10 19:41:34 laptop kernel: nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
>
> [snip]
>
>>
>> I won't get time tonight, but I can bisect it tomorrow, so this is just a heads up in case the problem (and fix) jumps
>> out at anyone. Before I bisect I'll build and run a kernel without the iwlwifi patches.
>
> The bisect ended up at:
>
> 7a3ef208e662f4b63d43a23f61a64a129c525bbc is the first bad commit
> commit 7a3ef208e662f4b63d43a23f61a64a129c525bbc
> Author: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> Date: Thu Jan 8 14:32:15 2015 -0800
>
> mm: prevent endless growth of anon_vma hierarchy
>
> Constantly forking task causes unlimited grow of anon_vma chain. Each
> next child allocates new level of anon_vmas and links vma to all
> previous levels because pages might be inherited from any level.
>
> This patch adds heuristic which decides to reuse existing anon_vma
> instead of forking new one. It adds counter anon_vma->degree which
> counts linked vmas and directly descending anon_vmas and reuses anon_vma
> if counter is lower than two. As a result each anon_vma has either vma
> or at least two descending anon_vmas. In such trees half of nodes are
> leafs with alive vmas, thus count of anon_vmas is no more than two times
> bigger than count of vmas.
>
> This heuristic reuses anon_vmas as few as possible because each reuse
> adds false aliasing among vmas and rmap walker ought to scan more ptes
> when it searches where page is might be mapped.
>
> Link: http://lkml.kernel.org/r/20120816024610.GA5350@xxxxxxxxxxxxxxxxxxxxxxx
> Fixes: 5beb49305251 ("mm: change anon_vma linking to fix multi-process server scalability issue")
> [akpm@xxxxxxxxxxxxxxxxxxxx: fix typo, per Rik]
> Signed-off-by: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
> Reported-by: Daniel Forrest <dan.forrest@xxxxxxxxxxxxx>
> Tested-by: Michal Hocko <mhocko@xxxxxxx>
> Tested-by: Jerome Marchand <jmarchan@xxxxxxxxxx>
> Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
> Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> [2.6.34+]
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
>
> :040000 040000 ca27f69d02743e7347b19b1e07976732a49698d1 7104c9ec5eb200ee4a21548e15d2b71a5806e107 M include
> :040000 040000 5440efbda5ac44c2a2da7e068f40ee6f0d4c0c7e b76fd93bffebec1acdef5f1785eb578c5f4f6cc3 M mm
>
> I'm more than happy to provide additional diagnostics and/or test any patches, but please cc me as I'm not subscribed.

Looks like degree (%edx) is 1 on anon-vma desruction.
Probably I've overlooked some weird conrner case in vma splitting/merging.

Could you try this patch. It disables vma merging end eliminates half
of complicated paths.
As I see merging is optional, everything should work fine without it.

--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1048,7 +1048,7 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm,
* We later require that vma->vm_flags == vm_flags,
* so this tests vma->vm_flags & VM_SPECIAL, too.
*/
- if (vm_flags & VM_SPECIAL)
+ if (1)
return NULL;

if (prev)

Code from your oops.

Code: 00 ad de 48 89 43 18 e8 c5 f9 00 00 48 8b 45 10 48 8d 55 10 48
83 e8 10 49 39 d6 74 54 48 8b 7d 08 48 89 eb 8b 57 34 85 d2 74 9e <0f>
0b 0f 1f 40 00 e8 6b fc ff ff eb 9a 66 0f 1f 84 00 00 00 00
All code
========
0: 00 ad de 48 89 43 add %ch,0x438948de(%rbp)
6: 18 e8 sbb %ch,%al
8: c5 f9 00 (bad)
b: 00 48 8b add %cl,-0x75(%rax)
e: 45 10 48 8d adc %r9b,-0x73(%r8)
12: 55 push %rbp
13: 10 48 83 adc %cl,-0x7d(%rax)
16: e8 10 49 39 d6 callq 0xffffffffd639492b
1b: 74 54 je 0x71
1d: 48 8b 7d 08 mov 0x8(%rbp),%rdi
21: 48 89 eb mov %rbp,%rbx
24: 8b 57 34 mov 0x34(%rdi),%edx
27: 85 d2 test %edx,%edx
29: 74 9e je 0xffffffffffffffc9
2b:* 0f 0b ud2 <-- trapping instruction
2d: 0f 1f 40 00 nopl 0x0(%rax)
31: e8 6b fc ff ff callq 0xfffffffffffffca1
36: eb 9a jmp 0xffffffffffffffd2
38: 66 data16
39: 0f .byte 0xf
3a: 1f (bad)
3b: 84 00 test %al,(%rax)
3d: 00 00 add %al,(%rax)
...

Code starting with the faulting instruction
===========================================
0: 0f 0b ud2
2: 0f 1f 40 00 nopl 0x0(%rax)
6: e8 6b fc ff ff callq 0xfffffffffffffc76
b: eb 9a jmp 0xffffffffffffffa7
d: 66 data16
e: 0f .byte 0xf
f: 1f (bad)
10: 84 00 test %al,(%rax)
12: 00 00 add %al,(%rax)

+Added Oded Gabbay <oded.gabbay@xxxxxxx> into cc, he's reported this
problem too.

>
> In case it helps, I've attached the xz-compressed related config file.
>
> Chris
>
>>
>> I've attached the full kernel log file for that boot.
>>
>> Chris
>>
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Next message: Baruch Siach: "Re: [PATCH v2 3/8] ARM: digicolor: add minimal device tree description"
Previous message: Boaz Harrosh: "Re: [PATCHSET 0/4 v4] brd: partition fixes"
In reply to: Chris Clayton: "Re: BUG in 3.19.0-rc3+"
Next in thread: Oded Gabbay: "Re: BUG in 3.19.0-rc3+"
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