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

[Chris Mason <clm@fb.com>]

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