linux-kernel - Re: [PATCH] rcu: better document kfree

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Message-ID: <20210115185450.GM2743@paulmck-ThinkPad-P72>
Date:   Fri, 15 Jan 2021 10:54:50 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Uladzislau Rezki <urezki@...il.com>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Joel Fernandes <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org
Subject: Re: [PATCH] rcu: better document kfree_rcu()

On Thu, Jan 14, 2021 at 12:36:19PM +0100, Uladzislau Rezki wrote:
> On Thu, Jan 14, 2021 at 08:22:02AM +0100, Mauro Carvalho Chehab wrote:
> > After changeset 5130b8fd0690 ("rcu: Introduce kfree_rcu() single-argument macro"),
> > kernel-doc now emits two warnings:
> > 
> > 	./include/linux/rcupdate.h:884: warning: Excess function parameter 'ptr' description in 'kfree_rcu'
> > 	./include/linux/rcupdate.h:884: warning: Excess function parameter 'rhf' description in 'kfree_rcu'
> > 
> > What's happening here is that some macro magic was added in order
> > to call two different versions of kfree_rcu(), being the first one
> > with just one argument and a second one with two arguments.
> > 
> > That makes harder to document the kfree_rcu() arguments, which
> > also reflects on the documentation text.
> > 
> > In order to make clearer that this macro accepts optional
> > arguments, by using macro concatenation, changing its
> > definition from:
> > 	#define kfree_rcu kvfree_rcu
> > 
> > to:
> > 	#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)
> > 
> > That not only helps kernel-doc to understand the macro arguemnts,
> > but also provides a better C definition that makes clearer that
> > the first argument is mandatory and the second one is optional.
> > 
> > Fixes: 5130b8fd0690 ("rcu: Introduce kfree_rcu() single-argument macro")
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> > ---
> >  include/linux/rcupdate.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> > index bd04f722714f..5cc6deaa5df2 100644
> > --- a/include/linux/rcupdate.h
> > +++ b/include/linux/rcupdate.h
> > @@ -881,7 +881,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> >   * The BUILD_BUG_ON check must not involve any function calls, hence the
> >   * checks are done in macros here.
> >   */
> > -#define kfree_rcu kvfree_rcu
> > +#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)
> >  
> >  /**
> >   * kvfree_rcu() - kvfree an object after a grace period.
> > -- 
> > 2.29.2
> > 
> I think it is fair enough. I checked the "kernel-doc" and after this
> change it does not detect any violations which are in question.
> 
> Tested-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Queued, thank you both!

							Thanx, Paul