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

- From: Luis Chamberlain \<mcgrof@kernel.org\>
- Date: 2021-10-26 17:02:09 
- List: linux-doc
- Page: https://ratatoskr.run/linux-doc/2021/10/217188
- Thread: https://ratatoskr.run/linux-doc/2021/09/215052/t/2.md

```text
On Tue, Oct 26, 2021 at 11:37:30PM +0800, Ming Lei wrote:
> On Tue, Oct 26, 2021 at 10:48:18AM +0200, Petr Mladek wrote:
> > Livepatch code never called kobject_del() under a lock. It would cause
> > the obvious deadlock.

Never?

> > The historic code only waited in the
> > module_exit() callback until the sysfs interface was removed.
> 
> OK, then Luis shouldn't consider livepatching as one such issue to solve
> with one generic solution.

It's not what I was told when the deadlock was found with zram, so I was
informed quite the contrary.

I'm working on a generic coccinelle patch which hunts for actual cases
using iteration (a feature of coccinelle for complex searches). The
search is pretty involved, so I don't think I'll have an answer to this
soon.

Since the question of how generic this deadlock is remains questionable,
I think it makes sense to put the generic deadlock fix off the table for
now, and we address this once we have a more concrete search with
coccinelle.

But to say we *don't* have drivers which can cause this is obviously
wrong as well, from a cursory search so far. But let's wait and see how
big this list actually is.

I'll drop the deadlock generic fixes and move on with at least a starter
kernfs / sysfs tests.

  Luis
```