Re: [PATCH 1/2] Allow a kthread to declare that it calls task_work_run()

[Christian Brauner <brauner@kernel.org>]

On Mon, Dec 04, 2023 at 03:09:44PM -0700, Jens Axboe wrote:
> On 12/4/23 2:02 PM, NeilBrown wrote:
> > It isn't clear to me what _GPL is appropriate, but maybe the rules
> > changed since last I looked..... are there rules?
> > 
> > My reasoning was that the call is effectively part of the user-space
> > ABI.  A user-space process can call this trivially by invoking any
> > system call.  The user-space ABI is explicitly a boundary which the GPL
> > does not cross.  So it doesn't seem appropriate to prevent non-GPL
> > kernel code from doing something that non-GPL user-space code can
> > trivially do.
> 
> By that reasoning, basically everything in the kernel should be non-GPL
> marked. And while task_work can get used by the application, it happens
> only indirectly or implicitly. So I don't think this reasoning is sound
> at all, it's not an exported ABI or API by itself.
> 
> For me, the more core of an export it is, the stronger the reason it
> should be GPL. FWIW, I don't think exporting task_work functionality is
> a good idea in the first place, but if there's a strong reason to do so,

Yeah, I'm not too fond of that part as well. I don't think we want to
give modules the ability to mess with task work. This is just asking for
trouble.