Re: [Xen-devel] kernel BUG at mm/swapfile.c:2524

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Apr 21, 2011 at 10:57:58AM -0400, Christopher S. Aker wrote:
> We're still getting reports of this occurring with 2.6.38 domU.

Darn. I was hoping it would have just disappeared on its own :-)

> Here's a fresh one:
> 
> ------------[ cut here ]------------
> kernel BUG at mm/swapfile.c:2524!
> invalid opcode: 0000 [#1] SMP
> last sysfs file: /sys/kernel/uevent_seqnum
> Modules linked in:
> 
> Pid: 12589, comm: apache2 Not tainted 2.6.38-linode31 #1
> EIP: 0061:[<c01a36b6>] EFLAGS: 00210246 CPU: 0
> EIP is at swap_count_continued+0x176/0x180
> EAX: f57ba6c3 EBX: ed3af500 ECX: f57ba000 EDX: 00000000
> ESI: ed3c5280 EDI: 00000080 EBP: 000006c3 ESP: d4bcde30
>  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
> Process apache2 (pid: 12589, ti=d4bcc000 task=ec9c17d0 task.ti=d4bcc000)
> Stack:
>  ec03c4c0 000166c3 00000000 00000000 c01a37b1 b7d63000 ec03c4c0 000166c3
>  00000000 c01a5b67 b7d63000 b7e00000 eae67b18 c0196296 6bb30067 80000006
>  c01039c6 0000000c 00000000 00000000 002cd860 0006c92f d0374df0 d17b3040
> Call Trace:
>  [<c01a37b1>] ? swap_entry_free+0xf1/0x120
>  [<c01a5b67>] ? free_swap_and_cache+0x27/0xd0
>  [<c0196296>] ? unmap_vmas+0x3d6/0x820
>  [<c01039c6>] ? __raw_callee_save_xen_make_pte+0x6/0x8
>  [<c019a7d1>] ? exit_mmap+0x91/0x140
>  [<c0130ceb>] ? mmput+0x2b/0xc0
>  [<c0134697>] ? exit_mm+0xe7/0x120
>  [<c063f390>] ? _raw_spin_lock_irq+0x10/0x20
>  [<c013614a>] ? do_exit+0x10a/0x6e0
>  [<c013675c>] ? do_group_exit+0x3c/0xa0
>  [<c01367d1>] ? sys_exit_group+0x11/0x20
>  [<c063f761>] ? syscall_call+0x7/0xb
>  [<c0630000>] ? sctp_sockaddr_af+0x20/0x90
> Code: ff 89 d8 e8 cd f7 f7 ff 01 e8 8d 76 00 c6 00 00 ba 01 00 00 00
> eb b2 89 f8 3c 80 0f 94 c0 e9 b9 fe ff ff 0f 0b e
> b fe 0f 0b eb fe <0f> 0b eb fe 0f 0b eb fe 66 90 83 ec 10 89 1c 24
> 89 c3 89 74 24
> EIP: [<c01a36b6>] swap_count_continued+0x176/0x180 SS:ESP 0069:d4bcde30
> ---[ end trace f3fdefcfb4d8b5dc ]---
> Fixing recursive fault but reboot is needed!
> BUG: scheduling while atomic: apache2/12589/0x00000001
> Modules linked in:
> Pid: 12589, comm: apache2 Tainted: G      D     2.6.38-linode31 #1

Aaah, so another HTTP server.

How can I reproduce this?
> Call Trace:
> 
>  [<c063d979>] ? schedule+0x6a9/0x8b0
>  [<c010630b>] ? xen_restore_fl_direct_end+0x0/0x1
>  [<c063f3b1>] ? _raw_spin_unlock_irqrestore+0x11/0x20
>  [<c0133323>] ? console_unlock+0x1c3/0x200
>  [<c013374f>] ? vprintk+0x17f/0x3c0
>  [<c01365ff>] ? do_exit+0x5bf/0x6e0
>  [<c063f367>] ? _raw_spin_lock_irqsave+0x27/0x40
>  [<c063f3b1>] ? _raw_spin_unlock_irqrestore+0x11/0x20
>  [<c0132e96>] ? kmsg_dump+0x36/0xf0
>  [<c0109a90>] ? do_invalid_op+0x0/0x90
>  [<c0109a90>] ? do_invalid_op+0x0/0x90
>  [<c010bea1>] ? oops_end+0x71/0xa0
>  [<c0109b0f>] ? do_invalid_op+0x7f/0x90
>  [<c01a36b6>] ? swap_count_continued+0x176/0x180
>  [<c016d805>] ? handle_IRQ_event+0x55/0xc0
>  [<c0105b37>] ? xen_force_evtchn_callback+0x17/0x30
>  [<c0138090>] ? __do_softirq+0x0/0x130
>  [<c0106314>] ? check_events+0x8/0xc
>  [<c010630b>] ? xen_restore_fl_direct_end+0x0/0x1
>  [<c010af92>] ? do_softirq+0x42/0xb0
>  [<c063fcd6>] ? error_code+0x5a/0x60
>  [<c012007b>] ? __change_page_attr_set_clr+0xa2b/0xb40
>  [<c0109a90>] ? do_invalid_op+0x0/0x90
>  [<c01a36b6>] ? swap_count_continued+0x176/0x180
>  [<c01a37b1>] ? swap_entry_free+0xf1/0x120
>  [<c01a5b67>] ? free_swap_and_cache+0x27/0xd0

So back to unmap_vmas. I wonder if we are missing the lazy_unmap flag
in 2.6.38.

>  [<c0196296>] ? unmap_vmas+0x3d6/0x820
>  [<c01039c6>] ? __raw_callee_save_xen_make_pte+0x6/0x8
>  [<c019a7d1>] ? exit_mmap+0x91/0x140
>  [<c0130ceb>] ? mmput+0x2b/0xc0
>  [<c0134697>] ? exit_mm+0xe7/0x120
>  [<c063f390>] ? _raw_spin_lock_irq+0x10/0x20
>  [<c013614a>] ? do_exit+0x10a/0x6e0
>  [<c013675c>] ? do_group_exit+0x3c/0xa0
>  [<c01367d1>] ? sys_exit_group+0x11/0x20
>  [<c063f761>] ? syscall_call+0x7/0xb
>  [<c0630000>] ? sctp_sockaddr_af+0x20/0x90
> 
> -Chris
> 
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