Re: 5.1 kernel: khugepaged stuck at 100%

[Oleksandr Natalenko]

Hi.

On Fri, Jun 07, 2019 at 09:40:52AM +0200, Max Kellermann wrote:
> On 2019/06/06 19:24, Max Kellermann <max@xxxxxxxx> wrote:
> > I have the same problem (kernel 5.1.7), but over here, it's a PHP
> > process, not khugepaged, which is looping inside compaction_alloc.
> 
> This is what happened an hour later:
> 
>  kernel tried to execute NX-protected page - exploit attempt? (uid: 33333)
>  BUG: unable to handle kernel paging request at ffffffffc036f00f
>  #PF error: [PROT] [INSTR]
>  PGD 35fa10067 P4D 35fa10067 PUD 35fa12067 PMD 105ba71067 PTE 800000022d28e061
>  Oops: 0011 [#1] SMP PTI
>  CPU: 12 PID: 263514 Comm: php-cgi7.0 Not tainted 5.1.7-cmag1-th+ #5
>  Hardware name: HP ProLiant DL380 Gen9/ProLiant DL380 Gen9, BIOS P89 10/17/2018
>  RIP: 0010:0xffffffffc036f00f
>  Code: Bad RIP value.
>  RSP: 0018:ffffb63c4d547928 EFLAGS: 00010216
>  RAX: 0000000000000000 RBX: ffffb63c4d547b10 RCX: 0000ffc004d021bd
>  RDX: ffff9ac83fffc500 RSI: 7fe0026810dee7ff RDI: 7fe0026810dee400
>  RBP: 7fe0026810dee400 R08: 0000000000000002 R09: 0000000000020300
>  R10: 00010642641a0d3a R11: 0000000000000001 R12: 7fe0026810dee800
>  R13: 0000000000000001 R14: 0000000000000000 R15: ffff9ac83fffc500
>  FS:  00007fa5c1000740(0000) GS:ffff9ad01f600000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: ffffffffc036efe5 CR3: 00000008eb8a0005 CR4: 00000000001606e0
>  Call Trace:
>   ? move_freelist_tail+0xd0/0xd0
>   ? migrate_pages+0xaa/0x780
>   ? isolate_freepages_block+0x380/0x380
>   ? compact_zone+0x6ec/0xca0
>   ? compact_zone_order+0xd8/0x120
>   ? try_to_compact_pages+0xb1/0x260
>   ? __alloc_pages_direct_compact+0x87/0x160
>   ? __alloc_pages_slowpath+0x427/0xd50
>   ? __alloc_pages_nodemask+0x2d6/0x310
>   ? do_huge_pmd_anonymous_page+0x131/0x680
>   ? vma_merge+0x24f/0x3a0
>   ? __handle_mm_fault+0xbca/0x1260
>   ? handle_mm_fault+0x135/0x1b0
>   ? __do_page_fault+0x242/0x4b0
>   ? page_fault+0x8/0x30
>   ? page_fault+0x1e/0x30
>  Modules linked in:
>  CR2: ffffffffc036f00f
>  ---[ end trace 0f31edf3041f5d9e ]---
>  RIP: 0010:0xffffffffc036f00f
>  Code: Bad RIP value.
>  RSP: 0018:ffffb63c4d547928 EFLAGS: 00010216
>  RAX: 0000000000000000 RBX: ffffb63c4d547b10 RCX: 0000ffc004d021bd
>  RDX: ffff9ac83fffc500 RSI: 7fe0026810dee7ff RDI: 7fe0026810dee400
>  RBP: 7fe0026810dee400 R08: 0000000000000002 R09: 0000000000020300
>  R10: 00010642641a0d3a R11: 0000000000000001 R12: 7fe0026810dee800
>  R13: 0000000000000001 R14: 0000000000000000 R15: ffff9ac83fffc500
>  FS:  00007fa5c1000740(0000) GS:ffff9ad01f600000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: ffffffffc036efe5 CR3: 00000008eb8a0005 CR4: 00000000001606e0

Make sure to check if e577c8b64d ("mm, compaction: make sure we isolate
a valid PFN") fixes your issue. It is staged for 5.1.8, BTW.

-- 
  Best regards,
    Oleksandr Natalenko (post-factum)
    Senior Software Maintenance Engineer