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

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Date:   Thu, 14 Jan 2021 08:22:02 +0100
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>
Cc:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        "Jonathan Corbet" <corbet@....net>,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        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: [PATCH] rcu: better document kfree_rcu()

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