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

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