RE: System reboot hangs due to race against devices_kset->listtriggered by SCSI FC workqueue

[Alan Stern]

On Wed, 3 Mar 2010, Hugh Daschbach wrote:

> > Can't we just protect the list?  What is wanting to write to the list
> > while shutdown is happening?
> 
> Indeed, Alan suggested holding the kset spinlock while iterating the
> list.  Unfortunately, the device shutdown routines may sleep.  At least
> the SCSI sd_shutdown routine issues I/O to the device as part of
> flushing device caches.  I would guess other subsystems sleep as well.

What I meant was that you should hold the spinlock while finding and 
unlinking the last device on the list.  Clearly you shouldn't hold it 
while calling the device shutdown routine.

> I'll try klist.  That looks like a good mediator between traversal and
> removal.

Yes, it removes a lot of difficulties.

Alan Stern

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