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Date: Wed, 26 Nov 2014 09:37:25 -0800
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Subject: Re: frequent lockups in 3.18rc4
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dave Jones <davej@redhat.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Juergen Gross <jgross@suse.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Nov 26, 2014 at 6:34 AM, Dave Jones <davej@redhat.com> wrote:
>
> Woke up to the below trace. Looks like a different issue.

Yeah, apparently the Xen issue was really just a Xen bug.

> NMI watchdog: BUG: soft lockup - CPU#2 stuck for 22s! [trinity-c149:24766]
> RIP: 0010:[<ffffffff8104658c>]  [<ffffffff8104658c>] kernel_map_pages+0xbc/0x120

Well, this one at least makes some amount of sense. The "Code:" line says it's

  1b: 9c                   pushfq
  1c: 5a                   pop    %rdx
  1d: fa                   cli
  1e: 0f 20 e0             mov    %cr4,%rax
  21: 48 89 c1             mov    %rax,%rcx
  24: 80 e1 7f             and    $0x7f,%cl
  27: 0f 22 e1             mov    %rcx,%cr4
  2a: 0f 22 e0             mov    %rax,%cr4
  2d: 52                   push   %rdx
  2e: 9d                   popfq
  2f:* eb cf                 jmp    back <-- trapping instruction

and %rdx is 0x0202 which is actually a valid flags value.

That looks like the code for __native_flush_tlb_global().

Not that interrupt should have been disabled very long.

> Call Trace:
>  [<ffffffff81185ebf>] get_page_from_freelist+0x49f/0xaa0
>  [<ffffffff811866ee>] __alloc_pages_nodemask+0x22e/0xb60
>  [<ffffffff811d093e>] alloc_pages_vma+0xee/0x1b0
>  [<ffffffff81194f0e>] shmem_alloc_page+0x6e/0xc0
>  [<ffffffff81197880>] shmem_getpage_gfp+0x4d0/0x7e0
>  [<ffffffff81197bd2>] shmem_write_begin+0x42/0x70
>  [<ffffffff8117c2d4>] generic_perform_write+0xd4/0x1f0
>  [<ffffffff8117eac2>] __generic_file_write_iter+0x162/0x350
>  [<ffffffff8117ecef>] generic_file_write_iter+0x3f/0xb0
>  [<ffffffff811f01b8>] do_iter_readv_writev+0x78/0xc0
>  [<ffffffff811f19e8>] do_readv_writev+0xd8/0x2a0
>  [<ffffffff811f1c3c>] vfs_writev+0x3c/0x50
>  [<ffffffff811f1dac>] SyS_writev+0x5c/0x100
>  [<ffffffff817e0249>] tracesys_phase2+0xd4/0xd9

Hmm. Maybe some oom issue, that we spent a long time before this
trying to free pages?

                  Linus
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