From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 59CFDC4332F for ; Mon, 13 Sep 2021 23:19:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C83C61130 for ; Mon, 13 Sep 2021 23:19:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244272AbhIMXUo (ORCPT ); Mon, 13 Sep 2021 19:20:44 -0400 Received: from mail.kernel.org ([198.145.29.99]:41602 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245070AbhIMXRw (ORCPT ); Mon, 13 Sep 2021 19:17:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 454F860FDA; Mon, 13 Sep 2021 23:04:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631574270; bh=Ub0V4Q81oxe1XsMj5ZBRwqtb17rpp6Rtp+hU97fNWPY=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=aApPjylgGlWmT+kikqn6rIM1HuUPQ6wUfTNKfdxKvCTgmn91wlKDUOomAf+VNbPzd nGMyt9a3eT8xHYcyiC/SJ6p7+Xo9mE2P6lprZyF8uihQuh7Ub5iKhhIATz3HhsBqsd gfVsP/vG6g8wiolbxHhz45gK772XyumNmOnkRVjWy6K4gVOWFVefGWsBaJgqzQf002 8bz5QJSyZKvqP50mTyI49Q6tXJ+wRu5JUGuxUzGcIqopa6TzXqljBDUIOev3mcCSDP EFC4iHOrsGpZQZCjMbmHZVXJ3mJVrXFBtBXzkcebAUPZJAKn8Dxc/KVIAQ1rbVF+cU A/pjjcLJJkDHQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 0E06F5C048F; Mon, 13 Sep 2021 16:04:30 -0700 (PDT) Date: Mon, 13 Sep 2021 16:04:30 -0700 From: "Paul E. McKenney" To: Chun-Hung Tseng Cc: josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Jim Huang Subject: Re: [PATCH] rcu: replace _________p1 with __UNIQUE_ID(rcu) Message-ID: <20210913230430.GM4156@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210912204131.93206-1-henrybear327@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210912204131.93206-1-henrybear327@gmail.com> Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, Sep 13, 2021 at 04:41:31AM +0800, Chun-Hung Tseng wrote: > This commit replaced _________p1 with __UNIQUE_ID(rcu), which > generates unique variable names during compilation. Necessary > modifications due to the changes in the RCU macros have also been > reflected in this commit. > > The same idea is used for the min/max macros (commit 589a978 and commit > e9092d0), which aims to reduce variable shadowing issues caused by hard > coded variable names. > > Signed-off-by: Jim Huang > Signed-off-by: Chun-Hung Tseng OK, I will bite... > --- > include/linux/rcupdate.h | 44 +++++++++++++++++++++++----------------- > include/linux/srcu.h | 3 ++- > 2 files changed, 27 insertions(+), 20 deletions(-) > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 434d12fe2d4f..a5ab20822040 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -370,39 +370,41 @@ static inline void rcu_preempt_sleep_check(void) { } > * Converts @p from an __rcu pointer to a __kernel pointer. > * This allows an __rcu pointer to be used with xchg() and friends. > */ > -#define unrcu_pointer(p) \ > +#define __unrcu_pointer(p, local) \ > ({ \ > - typeof(*p) *_________p1 = (typeof(*p) *__force)(p); \ > + typeof(*p) *local = (typeof(*p) *__force)(p); \ Why not like this? typeof(*p) *__UNIQUE_ID(rcu) = (typeof(*p) *__force)(p); \ Then we don't need the extra argument and the changes to the calls. So what C-preprocessor subtlety am I missing? Thanx, Paul > rcu_check_sparse(p, __rcu); \ > - ((typeof(*p) __force __kernel *)(_________p1)); \ > + ((typeof(*p) __force __kernel *)(local)); \ > }) > +#define unrcu_pointer(p) __unrcu_pointer(p, __UNIQUE_ID(rcu)) > > -#define __rcu_access_pointer(p, space) \ > +#define __rcu_access_pointer(p, local, space) \ > ({ \ > - typeof(*p) *_________p1 = (typeof(*p) *__force)READ_ONCE(p); \ > + typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ > rcu_check_sparse(p, space); \ > - ((typeof(*p) __force __kernel *)(_________p1)); \ > + ((typeof(*p) __force __kernel *)(local)); \ > }) > -#define __rcu_dereference_check(p, c, space) \ > +#define __rcu_dereference_check(p, local, c, space) \ > ({ \ > /* Dependency order vs. p above. */ \ > - typeof(*p) *________p1 = (typeof(*p) *__force)READ_ONCE(p); \ > + typeof(*p) *local = (typeof(*p) *__force)READ_ONCE(p); \ > RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_check() usage"); \ > rcu_check_sparse(p, space); \ > - ((typeof(*p) __force __kernel *)(________p1)); \ > + ((typeof(*p) __force __kernel *)(local)); \ > }) > -#define __rcu_dereference_protected(p, c, space) \ > +#define __rcu_dereference_protected(p, local, c, space) \ > ({ \ > RCU_LOCKDEP_WARN(!(c), "suspicious rcu_dereference_protected() usage"); \ > rcu_check_sparse(p, space); \ > ((typeof(*p) __force __kernel *)(p)); \ > }) > -#define rcu_dereference_raw(p) \ > +#define __rcu_dereference_raw(p, local) \ > ({ \ > /* Dependency order vs. p above. */ \ > - typeof(p) ________p1 = READ_ONCE(p); \ > - ((typeof(*p) __force __kernel *)(________p1)); \ > + typeof(p) local = READ_ONCE(p); \ > + ((typeof(*p) __force __kernel *)(local)); \ > }) > +#define rcu_dereference_raw(p) __rcu_dereference_raw(p, __UNIQUE_ID(rcu)) > > /** > * RCU_INITIALIZER() - statically initialize an RCU-protected global variable > @@ -489,7 +491,7 @@ do { \ > * when tearing down multi-linked structures after a grace period > * has elapsed. > */ > -#define rcu_access_pointer(p) __rcu_access_pointer((p), __rcu) > +#define rcu_access_pointer(p) __rcu_access_pointer((p), __UNIQUE_ID(rcu), __rcu) > > /** > * rcu_dereference_check() - rcu_dereference with debug checking > @@ -525,7 +527,8 @@ do { \ > * annotated as __rcu. > */ > #define rcu_dereference_check(p, c) \ > - __rcu_dereference_check((p), (c) || rcu_read_lock_held(), __rcu) > + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ > + (c) || rcu_read_lock_held(), __rcu) > > /** > * rcu_dereference_bh_check() - rcu_dereference_bh with debug checking > @@ -540,7 +543,8 @@ do { \ > * rcu_read_lock() but also rcu_read_lock_bh() into account. > */ > #define rcu_dereference_bh_check(p, c) \ > - __rcu_dereference_check((p), (c) || rcu_read_lock_bh_held(), __rcu) > + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ > + (c) || rcu_read_lock_bh_held(), __rcu) > > /** > * rcu_dereference_sched_check() - rcu_dereference_sched with debug checking > @@ -555,7 +559,8 @@ do { \ > * only rcu_read_lock() but also rcu_read_lock_sched() into account. > */ > #define rcu_dereference_sched_check(p, c) \ > - __rcu_dereference_check((p), (c) || rcu_read_lock_sched_held(), \ > + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ > + (c) || rcu_read_lock_sched_held(), \ > __rcu) > > /* > @@ -565,7 +570,8 @@ do { \ > * The no-tracing version of rcu_dereference_raw() must not call > * rcu_read_lock_held(). > */ > -#define rcu_dereference_raw_check(p) __rcu_dereference_check((p), 1, __rcu) > +#define rcu_dereference_raw_check(p) \ > + __rcu_dereference_check((p), __UNIQUE_ID(rcu), 1, __rcu) > > /** > * rcu_dereference_protected() - fetch RCU pointer when updates prevented > @@ -584,7 +590,7 @@ do { \ > * but very ugly failures. > */ > #define rcu_dereference_protected(p, c) \ > - __rcu_dereference_protected((p), (c), __rcu) > + __rcu_dereference_protected((p), __UNIQUE_ID(rcu), (c), __rcu) > > > /** > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > index e6011a9975af..01226e4d960a 100644 > --- a/include/linux/srcu.h > +++ b/include/linux/srcu.h > @@ -117,7 +117,8 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp) > * lockdep_is_held() calls. > */ > #define srcu_dereference_check(p, ssp, c) \ > - __rcu_dereference_check((p), (c) || srcu_read_lock_held(ssp), __rcu) > + __rcu_dereference_check((p), __UNIQUE_ID(rcu), \ > + (c) || srcu_read_lock_held(ssp), __rcu) > > /** > * srcu_dereference - fetch SRCU-protected pointer for later dereferencing > -- > 2.25.1 >