Re: [PATCH 1/2] zram: fix crashes due to use of cpu hotplug multistate

From: Josh Poimboeuf
Date: Wed Apr 07 2021 - 16:18:05 EST


On Fri, Apr 02, 2021 at 09:54:12AM +0200, Greg KH wrote:
> On Thu, Apr 01, 2021 at 11:59:25PM +0000, Luis Chamberlain wrote:
> > As for the syfs deadlock possible with drivers, this fixes it in a generic way:
> >
> > commit fac43d8025727a74f80a183cc5eb74ed902a5d14
> > Author: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> > Date: Sat Mar 27 14:58:15 2021 +0000
> >
> > sysfs: add optional module_owner to attribute
> >
> > This is needed as otherwise the owner of the attribute
> > or group read/store might have a shared lock used on driver removal,
> > and deadlock if we race with driver removal.
> >
> > Signed-off-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
>
> No, please no. Module removal is a "best effort", if the system dies
> when it happens, that's on you. I am not willing to expend extra energy
> and maintance of core things like sysfs for stuff like this that does
> not matter in any system other than a developer's box.

So I mentioned this on IRC, and some folks were surprised to hear that
module unloading is unsupported and is just a development aid.

Is this stance documented anywhere?

If we really believe this to be true, we should make rmmod taint the
kernel.

--
Josh