Erase race?

[Jon Ringle]

On Tue, Apr 27, 2010 at 8:59 AM, Artem Bityutskiy <dedekind1 at gmail.com> wrote:
> On Tue, 2010-04-20 at 16:24 -0400, Jon Ringle wrote:
>> On Tue, Apr 13, 2010 at 4:15 PM, Jon Ringle <jon at ringle.org> wrote:
>> > Hi,
>> > I have a few machines that have UBI and UBIFS on NOR flash that are
>> > undergoing continuous reboot testing.
>> > One of them just caught the following failure:
>> >
>> > [   51.250000] IXP4XX-Flash.0: buffer write error (status 0xd0)
>> > [   51.250000] UBI error: ubi_io_write: error -22 while writing 64
>> > bytes to PEB 226:0, written 0 bytes
>> > [   51.270000] UBI error: erase_worker: failed to erase PEB 226, error -22
>> > [   51.270000] UBI warning: ubi_ro_mode: switch to read-only mode
>> > [   51.290000] UBI error: do_work: work failed with error code -22
>> > [   51.290000] UBI error: ubi_thread: ubi_bgt0d: work failed with error code -22
>> >
>> > Looking at this it appears that the failure might have been caused due
>> > to the erase_worker and ubi_io_write occurring out of order... since
>> > it looks like ubi_io_write was trying to write at offset 0 of the PEB,
>> > which I imagine would have to be the EC header, which should happen
>> > after the block is erased. But it doesn't seem to be the case here.
>>
>> I had this issue occur again on another system:
>> [   48.250000] IXP4XX-Flash.0: buffer write error (status 0xd0)
>> [   48.250000] UBI error: ubi_io_write: error -22 while writing 64
>> bytes to PEB 111:0, written 0 bytes
>> [   48.280000] UBI error: erase_worker: failed to erase PEB 111, error -22
>> [   48.280000] UBI warning: ubi_ro_mode: switch to read-only mode
>> [   48.310000] UBI error: do_work: work failed with error code -22
>> [   48.310000] UBI error: ubi_thread: ubi_bgt0d: work failed with error code -22
>>
>> Can anyone comment as to my theory that this is a race condition
>> between ubi_io_write and erase_worker occurring out of order?
>
> Did you debug this further? Any new findings?

I finally got a capture of this with CONFIG_MTD_UBI_DEBUG turned on:

[   61.710000] IXP4XX-Flash.0: buffer write error (status 0xd0)
[   61.710000] UBI error: ubi_io_write: error -22 while writing 64
bytes to PEB 136:0, written 0 bytes
[   61.740000] [<c011a240>] (unwind_backtrace+0x0/0x170) from
[<bf0157a8>] (ubi_io_write+0x1ec/0x214 [ubi])
[   61.770000] [<bf0157a8>] (ubi_io_write+0x1ec/0x214 [ubi]) from
[<bf01599c>] (ubi_io_write_vid_hdr+0x1cc/0x20c [ubi])
[   61.800000] [<bf01599c>] (ubi_io_write_vid_hdr+0x1cc/0x20c [ubi])
from [<bf016c50>] (sync_erase+0xd4/0x128 [ubi])
[   61.830000] [<bf016c50>] (sync_erase+0xd4/0x128 [ubi]) from
[<bf017344>] (erase_worker+0x28/0x2d8 [ubi])
[   61.860000] [<bf017344>] (erase_worker+0x28/0x2d8 [ubi]) from
[<bf0180e4>] (do_work+0x98/0x13c [ubi])
[   61.860000] [<bf0180e4>] (do_work+0x98/0x13c [ubi]) from
[<bf01824c>] (ubi_thread+0xc4/0x158 [ubi])
[   61.890000] [<bf01824c>] (ubi_thread+0xc4/0x158 [ubi]) from
[<c0142b84>] (kthread+0x7c/0x84)
[   61.890000] [<c0142b84>] (kthread+0x7c/0x84) from [<c0115378>]
(kernel_thread_exit+0x0/0x8)
[   61.920000] UBI error: erase_worker: failed to erase PEB 136, error -22
[   61.920000] UBI warning: ubi_ro_mode: switch to read-only mode
[   61.950000] UBI error: do_work: work failed with error code -22
[   61.950000] UBI error: ubi_thread: ubi_bgt0d: work failed with error code -22


>
> --
> Best Regards,
> Artem Bityutskiy (Артём Битюцкий)
>
>
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