Re: soft lockup - CPU#0 stuck - Kernel 3.17.2

[Patrick Schmid <schmid@phys.ethz.ch>]

On 11/13/2014 03:49 PM, Chris Mason wrote:
>
>
> On Thu, Nov 13, 2014 at 8:32 AM, Patrick Schmid <schmid@phys.ethz.ch>
> wrote:
>> Hi all,
>>
>> we run a > 500 TiB backup system on iSCSI targets using 19 BTRFS
>> filesystems (the biggest of which is 110 TiB) on Ubuntu 14.04 LTS and
>> various kernel versions. Btrfs-Progs v3.17.1. The hardware is a 24
>> core
>> Xeon E5-2620 on an Intel S2600GZ board with 128 GiB RAM.
>>
>> Since btrfs has changed to kworkers (I think in 3.15) the frontend
>> server somewhat randomly crashes with soft lockups (see attachment).
>> The
>> system is rock solid with the 3.14.22 kernel.
>>
>> The lockups happen during the nightly cron-controlled rsync backups
>> and
>> occur at random times during this process.
>> We are totally aware of the fact that this tends to be one of
>> those “it doesn’t work” bug reports, but
>> it’s really hard to pin
>> down the source of the problem other than it seems to be related to
>> the
>> kworkers. We’d love to provide any feedback we can, please let
>> us know
>> what you need.
>
> Hi,
>
> This may actually be related to a different btrfs change in the 3.15
> kernel.  Do you see more than one soft lockup?  After the softlockup,
> does the box recover or is it stuck forever?
>
> -chris
>

Hi Chris

"Normaly" are there more than one soft lockup and the load goes up to 
sky and the server stuck forever until hard reset.

If you want, i send you tomorrow morning the whole kernel log?

regards
Patrick