linux-kernel - Re: [PATCH v14 05/11] livepatch: Simplify API by removing registration step

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Date:   Thu, 6 Dec 2018 10:23:40 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Petr Mladek <pmladek@...e.com>
cc:     Joe Lawrence <joe.lawrence@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Evgenii Shatokhin <eshatokhin@...tuozzo.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v14 05/11] livepatch: Simplify API by removing registration
 step

On Thu, 6 Dec 2018, Petr Mladek wrote:

> On Wed 2018-12-05 14:32:53, Joe Lawrence wrote:
> > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > > index 972520144713..e01dfa3b58d2 100644
> > > --- a/kernel/livepatch/core.c
> > > +++ b/kernel/livepatch/core.c
> > > @@ -45,7 +45,7 @@
> > >   */
> > >  DEFINE_MUTEX(klp_mutex);
> > >  
> > > -/* Registered patches */
> > > +/* Actively used patches. */
> > >  LIST_HEAD(klp_patches);
> > 
> > By itself, this comment makes me wonder if there are un-active and/or
> > un-used patches that I need to worry about.  After this patchset,
> > klp_patches will include patches that have been enabled and those that
> > have been replaced, but the replacement transition is still in progress.  
> > 
> > If that sounds accurate, how about adding to the comment:
> > 
> > /* Actively used patches: enabled or replaced and awaiting transition */
> 
> The replaced patches are not in the list. This is why I used the word
> "actively".

The replaced patches are removed in klp_discard_replaced_patches(), which 
is called from klp_complete_transition(). Joe is right. The patches are in 
the list if a transition is still in progress.

Miroslav
 
> /*
>  * Actively used patches: enabled or in transition. Note that replaced
>  * or disabled patches are not listed even though the related kernel
>  * module still can be loaded.
>  */