Re: kernel oops on mmotm-2015-10-15-15-20

[Minchan Kim]

On Mon, Nov 16, 2015 at 12:54:53PM +0200, Kirill A. Shutemov wrote:
> On Mon, Nov 16, 2015 at 07:32:20PM +0900, Minchan Kim wrote:
> > On Mon, Nov 16, 2015 at 10:45:22AM +0200, Kirill A. Shutemov wrote:
> > > On Mon, Nov 16, 2015 at 10:45:21AM +0900, Minchan Kim wrote:
> > > > During the test with MADV_FREE on kernel I applied your patches,
> > > > I couldn't see any problem.
> > > > 
> > > > However, in this round, I did another test which is same one
> > > > I attached but a liitle bit different because it doesn't do
> > > > (memcg things/kill/swapoff) for testing program long-live test.
> > > 
> > > Could you share updated test?
> > 
> > It's part of my testing suite so I should factor it out.
> > I will send it when I go to office tomorrow.
> 
> Thanks.
> 
> > > And could you try to reproduce it on clean mmotm-2015-11-10-15-53?
> > 
> > Befor leaving office, I queued it up and result is below.
> > It seems you fixed already but didn't apply it to mmotm yet. Right?
> > Anyway, please confirm and say to me what I should add more patches
> > into mmotm-2015-11-10-15-53 for follow up your recent many bug
> > fix patches.
> 
> The two my patches which are not in the mmotm-2015-11-10-15-53 release:
> 
> http://lkml.kernel.org/g/1447236557-68682-1-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx
> http://lkml.kernel.org/g/1447236567-68751-1-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx

1. mm: fix __page_mapcount()
2. thp: fix leak due split_huge_page() vs. exit race

If I missed some patches, let me know it.

I applied above two patches based on mmotm-2015-11-10-15-53 and tested again.
But unfortunately, the result was below.

Now, I am making test program I can send to you but it seems to be not easy
because small changes for factoring it out from testing suite seems to change
something(ex, timing) and makes hard to reproduce. I will try it again.


page:ffffea0000240080 count:2 mapcount:1 mapping:ffff88007eff3321 index:0x600000e02
flags: 0x4000000000040018(uptodate|dirty|swapbacked)
page dumped because: VM_BUG_ON_PAGE(!PageLocked(page))
page->mem_cgroup:ffff880077cf0c00
------------[ cut here ]------------
kernel BUG at mm/huge_memory.c:3272!
invalid opcode: 0000 [#1] SMP 
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 8 PID: 59 Comm: khugepaged Not tainted 4.3.0-mm1-kirill+ #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff880073441a40 ti: ffff88007344c000 task.ti: ffff88007344c000
RIP: 0010:[<ffffffff8114bc9b>]  [<ffffffff8114bc9b>] split_huge_page_to_list+0x8fb/0x910
RSP: 0018:ffff88007344f968  EFLAGS: 00010286
RAX: 0000000000000021 RBX: ffffea0000240080 RCX: 0000000000000000
RDX: 0000000000000001 RSI: 0000000000000246 RDI: ffffffff821df4d8
RBP: ffff88007344f9e8 R08: 0000000000000000 R09: ffff8800000bc600
R10: ffffffff8163e2c0 R11: 0000000000004b47 R12: ffffea0000240080
R13: ffffea0000240088 R14: ffffea0000240080 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff880078300000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007ffd59edcd68 CR3: 0000000001808000 CR4: 00000000000006a0
Stack:
 cccccccccccccccd ffffea0000240080 ffff88007344fa00 ffffea0000240088
 ffff88007344fa00 0000000000000000 ffff88007344f9e8 ffffffff810f0200
 ffffea0000240000 0000000000000000 0000000000000000 ffffea0000240080
Call Trace:
 [<ffffffff810f0200>] ? __lock_page+0xa0/0xb0
 [<ffffffff8114bdc5>] deferred_split_scan+0x115/0x240
 [<ffffffff8111851c>] ? list_lru_count_one+0x1c/0x30
 [<ffffffff811018d3>] shrink_slab.part.42+0x1e3/0x350
 [<ffffffff8110644a>] shrink_zone+0x26a/0x280
 [<ffffffff8110658d>] do_try_to_free_pages+0x12d/0x3b0
 [<ffffffff811068c4>] try_to_free_pages+0xb4/0x140
 [<ffffffff810f9279>] __alloc_pages_nodemask+0x459/0x920
 [<ffffffff8108d750>] ? trace_event_raw_event_tick_stop+0xd0/0xd0
 [<ffffffff81147465>] khugepaged+0x155/0x1b10
 [<ffffffff81073ca0>] ? prepare_to_wait_event+0xf0/0xf0
 [<ffffffff81147310>] ? __split_huge_pmd_locked+0x4e0/0x4e0
 [<ffffffff81057e49>] kthread+0xc9/0xe0
 [<ffffffff81057d80>] ? kthread_park+0x60/0x60
 [<ffffffff8142aa6f>] ret_from_fork+0x3f/0x70
 [<ffffffff81057d80>] ? kthread_park+0x60/0x60
Code: ff ff 48 c7 c6 00 cd 77 81 4c 89 f7 e8 df ce fc ff 0f 0b 48 83 e8 01 e9 94 f7 ff ff 48 c7 c6 80 bb 77 81 4c 89 f7 e8 c5 ce fc ff <0f> 0b 48 c7 c6 48 c9 77 81 4c 89 e7 e8 b4 ce fc ff 0f 0b 66 90 
RIP  [<ffffffff8114bc9b>] split_huge_page_to_list+0x8fb/0x910
 RSP <ffff88007344f968>
---[ end trace 0ee39378e850d8de ]---
Kernel panic - not syncing: Fatal exception
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
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