Re: [PATCH v8 11/12] zram: fix crashes with cpu hotplug multistate

Luis Chamberlain
2021-10-19T19:38:56Z

On Wed, Oct 20, 2021 at 12:39:22AM +0800, Ming Lei wrote:
> On Tue, Oct 19, 2021 at 08:50:24AM -0700, Luis Chamberlain wrote:
> > So do you want to take the position:
> >
> > Hey driver authors: you cannot use any shared lock on module removal and
> > on sysfs ops?
>
> IMO, yes, in your patch of 'zram: fix crashes with cpu hotplug multistate',
> when you added mutex_lock(zram_index_mutex) to disksize_store() and
> other attribute show() or store() method. You have added new deadlock
> between hot_remove_store() and disksize_store() & others, which can't be
> addressed by your approach of holding module refcnt.
>
> So far not see ltp tests covers hot add/remove interface yet.

Care to show what commands to use to cause this deadlock with my patches?

Luis