Re: [PATCH] livepatch: support for repatching a function

From: Josh Poimboeuf
Date: Mon Jan 19 2015 - 15:02:49 EST


On Mon, Jan 19, 2015 at 08:48:42PM +0100, Jiri Kosina wrote:
> On Mon, 19 Jan 2015, Josh Poimboeuf wrote:
>
> > > If this is implemented really in a fully stackable manner (i.e. you
> > > basically would be able to disable only the function that is currently
> > > "active", i.e. on top of the stack), woudln't that provide more
> > > predictable semantics?
> >
> > Yes, I agree. Thanks for the comment.
> >
> > Would you want to enforce stacking even if there are no dependencies
> > between the patches? I think that would be easiest (and cleanest).
>
> Yup, I think that makes the most sense (especially in this "first step").
> Relaxing the revert rules to cover only patches which are really dependent
> on each other (and we'd have to be careful about defining the meaning
> this, especially with repsect to various consistency models coming in the
> future) is something tha can always be done later on top.

Sounds good. I'll do a v2.

FYI, I've also been working on a prototype of a consistency model, based
on my discussions with Vojtech on the list a few months ago
(LEAVE_PATCHED_SET + SWITCH_THREAD). I'll probably have some patches to
send out for comments in a few weeks. That should hopefully be a good
starting point for more discussion about the consistency model(s).

--
Josh
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