Re: Kernel Oops on enabling CONFIG_LOCK_STAT

[Shreshtha]

Hi Tejun Heo,

Problem persists even after applying the patch.
After applying the debug patch (and printk for rs,re etc.) related
output in mail below.

The log attached was with linux-2.6.35.7 kernel.
I tried newer kernel i.e. 2.6.39.3 and problem was *not* seen.
Seems that changes in mm/* solved the issue.
So I will take this thread from here.

Thanks for debug patch.

------------8<-------------------------------8<-------------
BOARD - 1
-----------

WARNING: at mm/percpu-vm.c:360 pcpu_alloc+0x360/0x9e4()
Modules linked in:
[<c0ce1148>] (unwind_backtrace+0x0/0xf0) from [<c0cf67d8>]
(warn_slowpath_common+0x4c/0x64)
[<c0cf67d8>] (warn_slowpath_common+0x4c/0x64) from [<c0cf6808>]
(warn_slowpath_null+0x18/0x1c)
[<c0cf6808>] (warn_slowpath_null+0x18/0x1c) from [<c0d56708>]
(pcpu_alloc+0x360/0x9e4)
[<c0d56708>] (pcpu_alloc+0x360/0x9e4) from [<c0d53110>]
(kmem_cache_open+0x17c/0x1ec)
[<c0d53110>] (kmem_cache_open+0x17c/0x1ec) from [<c0d54e48>]
(kmem_cache_create+0x1e0/0x2b4)
[<c0d54e48>] (kmem_cache_create+0x1e0/0x2b4) from [<c0017b98>]
(idr_init_cache+0x20/0x34)
[<c0017b98>] (idr_init_cache+0x20/0x34) from [<c0008d24>]
(start_kernel+0x244/0x30c)
[<c0008d24>] (start_kernel+0x244/0x30c) from [<00008080>] (0x8080)
---[ end trace 1b75b31a2719ed1d ]---
XXX pcpu_populate_chunk: cpu0: rs: 0x162, re: 0x166, page start: 0x162
end: 0x163
XXX pcpu_populate_chunk: cpu1: rs: 0x162, re: 0x166, page start: 0x162
end: 0x163


BOARD (newer) - 2
-----------
config_lock_stat-board2.log attached

-----------------8<---------------------8<----------------------------

Regards,
Shreshtha

On Fri, Jul 22, 2011 at 1:04 PM, Tejun Heo <tj@xxxxxxxxxx> wrote:
> Hello,
>
> On Fri, Jul 22, 2011 at 08:10:54AM +0200, Tejun Heo wrote:
>> Hrmm... so it's pcpu_populate_chunk() failure path.  Can you please
>> attach full kernel log?  Attaching full kernel log and including a bit
>> of hardware details is generally a good idea when reporting a bug.
>>
>> It's most likely there's a bug in the code which rolls back from
>> partial allocation after encountering alloc failure in the middle.
>> I'll take a deeper look there and report what I find.
>
> The code looks correct and seems to behave correct under induced
> error.  Can you please apply the following patch and see whether the
> problem goes away?
>
> diff --git a/mm/percpu-vm.c b/mm/percpu-vm.c
> index ea53496..53eae44 100644
> --- a/mm/percpu-vm.c
> +++ b/mm/percpu-vm.c
> @@ -347,6 +347,7 @@ clear:
>        return 0;
>
>  err_unmap:
> +       pcpu_post_map_flush(chunk, page_start, unmap_end);
>        pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
>        pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
>                pcpu_unmap_pages(chunk, pages, populated, rs, re);
>
> If not, can you please apply the attached debug patch, trigger the
> problem and post the log?
>
> Thank you.
>
> --
> tejun
>

Attachment: config_lock_stat-board2.log
Description: Binary data

Attachment: config_2-6-35-7_lock_stat
Description: Binary data

Attachment: linux-2-6-35-7_lock_stat-debug.log
Description: Binary data