Re: [POC 0/7] livepatch: Make livepatch states, callbacks, and shadow variables work together

[Miroslav Benes]

On Fri, 10 Nov 2023, Josh Poimboeuf wrote:

> On Fri, Nov 10, 2023 at 06:04:21PM +0100, Petr Mladek wrote:
> > This POC is a material for the discussion "Simplify Livepatch Callbacks,
> > Shadow Variables, and States handling" at LPC 2013, see
> > https://lpc.events/event/17/contributions/1541/
> > 
> > It obsoletes the patchset adding the garbage collection of shadow
> > variables. This new solution is based on ideas from Nicolai Stange.
> > And it should also be in sync with Josh's ideas mentioned into
> > the thread about the garbage collection, see
> > https://lore.kernel.org/r/20230204235910.4j4ame5ntqogqi7m@treble
> 
> Nice!  I like how it brings the "features" together and makes them easy
> to use.  This looks like a vast improvement.
> 
> Was there a reason to change the naming?  I'm thinking
> 
>   setup / enable / disable / release
> 
> is less precise than
> 
>   pre_patch / post_patch / pre_unpatch / post_unpatch.
> 
> Also, I'm thinking "replaced" instead of "obsolete" would be more
> consistent with the existing terminology.
> 
> For example, in __klp_enable_patch():
> 
> 	ret = klp_setup_states(patch);
> 	if (ret)
> 		goto err;
> 
> 	if (patch->replace)
> 		klp_disable_obsolete_states(patch);
> 
> it's not immediately clear why "disable obsolete" would be the "replace"
> counterpart to "setup".
> 
> Similarly, in klp_complete_transition():
> 
> 	if (klp_transition_patch->replace && klp_target_state == KLP_PATCHED) {
> 		klp_unpatch_replaced_patches(klp_transition_patch);
> 		klp_discard_nops(klp_transition_patch);
> 		klp_release_obsolete_states(klp_transition_patch);
> 	}
> 
> it's a little jarring to have "unpatch replaced" followed by "release
> obsolete".

I agree. I would also stick to the existing naming. It is clearer to me.

Miroslav