XFS: Observed Crash followed by deadlock of khubd/sync/XFS

[Christoph Hellwig]

On Thu, Sep 08, 2011 at 10:58:35PM +0530, Amit Sahrawat wrote:
> Since this is very hard to reproduce, to make it easy to debug. This
> can be reproduce by introducing msleep in the kernel xfs_umountfs()
> before xfs_log_sbcount(), just add a print before this function and
> sleep and the moment the print appear unplug the USB device, same
> scenario will be reproduced.
> CRASH will show the backtrace and return to normal shell, but when
> process state is checked, khubd will be shown in TASK-UNINTERRUPTIBLE
> state 'D'.
> Further if sync is issued that will also get converted to 'D' state,
> the back-trace for each of the task is same as mentioned in the
> previous mail.

I've not been able to reproduce this using that method so far.