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SubjectRe: perf bug: bad page map
On Mon, 18 Nov 2013, Peter Zijlstra wrote:

> On Fri, Nov 15, 2013 at 01:04:23PM -0500, Vince Weaver wrote:
> >
> > (figured out the minicom issue).
> >
> > Anyway while trying to reproduce the last bug I instead got this with
> > the perf_fuzzer.
> >
> > Is it worth continuing to run and report these issues? I'm losing track
> > of all the open bugs.
>
> This is looks like ext4. Not entirely sure how perf ties into this.

It's believable the filesystem could have issues (it's a fuzzer machine,
so it's had 100+ unclean shutdowns on an SSD drive in the past few months)
but as far as I know there shouldn't have been any filesystem accesses
happening at all when the bug triggered.

I thought it might be perf related due to the perf references in the
backtrace (and since it was being perf-fuzzed at the time).

> Anyway, yes, I do think its useful to keep running these tests, we do
> fix various issues -- although probably not at the rate you seem to be
> finding them.
>
> > [ 1618.118179] BUG: Bad page map in process perf_fuzzer pte:ffff8800c4d60040 pmd:bd86a067
> > [ 1618.142177] addr:0000000000409000 vm_flags:00000875 anon_vma: (null) mapping:ffff8800cb74adf0 index:9
> > [ 1618.172142] vma->vm_ops->fault: filemap_fault+0x0/0x358
> > [ 1618.187783] vma->vm_file->f_op->mmap: ext4_file_mmap+0x0/0x48
> > [ 1618.204981] CPU: 1 PID: 24819 Comm: perf_fuzzer Not tainted 3.12.0 #4
> > [ 1618.224256] Hardware name: AOpen DE7000/nMCP7ALPx-DE R1.06 Oct.19.2012, BIOS 080015 10/19/2012
> > [ 1618.250825] 0000000000409000 ffff8800bf6dfaa8 ffffffff8151d8ec 0000000000000000
> > [ 1618.273081] ffff8800c89ac928 ffff8800bf6dfaf8 ffffffff810ed692 dead000000200200
> > [ 1618.295345] 00000000c03df067 ffff8800bf6dfbe8 0000000000409000 ffffea0002bc2fe8
> > [ 1618.317603] Call Trace:
> > [ 1618.324951] [<ffffffff8151d8ec>] dump_stack+0x49/0x5d
> > [ 1618.340355] [<ffffffff810ed692>] print_bad_pte+0x1f5/0x213
> > [ 1618.357059] [<ffffffff810ef43c>] unmap_single_vma+0x511/0x666
> > [ 1618.374540] [<ffffffff810ef5c3>] unmap_vmas+0x32/0x49
> > [ 1618.389934] [<ffffffff810f3804>] exit_mmap+0x84/0x10d
> > [ 1618.405343] [<ffffffff8105bb15>] ? hrtimer_try_to_cancel+0x41/0x4b
> > [ 1618.424129] [<ffffffff8103ac43>] mmput+0x4b/0xd1
> > [ 1618.438227] [<ffffffff8103ec76>] do_exit+0x36c/0x936
> > [ 1618.453366] [<ffffffff810c7312>] ? update_context_time+0x11/0x34
> > [ 1618.471628] [<ffffffff8100951b>] ? native_sched_clock+0x3b/0x3d
> > [ 1618.489635] [<ffffffff8106730d>] ? sched_clock_local+0x1c/0x82
> > [ 1618.507376] [<ffffffff8103f2b8>] do_group_exit+0x78/0xa0
> > [ 1618.523563] [<ffffffff8104c898>] get_signal_to_deliver+0x46d/0x48a
> > [ 1618.542347] [<ffffffff810c8ac7>] ? ctx_sched_in+0x35/0x185
> > [ 1618.559051] [<ffffffff810c8c80>] ? perf_event_sched_in+0x69/0x72
> > [ 1618.577318] [<ffffffff81002513>] do_signal+0x46/0x5f5
> > [ 1618.592724] [<ffffffff810c8ffe>] ? __perf_event_task_sched_in+0x3a/0x10e
> > [ 1618.613071] [<ffffffff8106699f>] ? finish_task_switch+0x46/0x98
> > [ 1618.631075] [<ffffffff8151f832>] ? __schedule+0x51c/0x54b
> > [ 1618.647516] [<ffffffff81002aee>] do_notify_resume+0x2c/0x64
> > [ 1618.664486] [<ffffffff81520ef5>] retint_signal+0x3d/0x78
> > [ 1618.680661] Disabling lock debugging due to kernel taint


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