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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 550DFCA9EA0 for ; Tue, 22 Oct 2019 19:12:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25BEC21872 for ; Tue, 22 Oct 2019 19:12:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571771544; bh=x0hWzsK+SyGvpdoXV2Qzb3lMOfU9IISAP3AHFmIYd1g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=j6XFe0+o2XpaadmFyHm1B1sU2ItFHx+JRNawMbqfpryt0yNPH7VroOcv2e0N/UZ/p H+kWrJlL+zZRyXk0bkTapPQISQrxSMkww0vwxsWabuNG0JFv3BRryCKj8YsuzHyj23 PM50+SheRbH4+jTfIsBNHglPy5+KL/8Wzo1AD87k= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732905AbfJVTMX (ORCPT ); Tue, 22 Oct 2019 15:12:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:43238 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729696AbfJVTMV (ORCPT ); Tue, 22 Oct 2019 15:12:21 -0400 Received: from localhost.localdomain (rrcs-50-75-166-42.nys.biz.rr.com [50.75.166.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A732021783; Tue, 22 Oct 2019 19:12:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571771540; bh=x0hWzsK+SyGvpdoXV2Qzb3lMOfU9IISAP3AHFmIYd1g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BhUOdhzl+jIqtkc2bGLEztfls5oh/lSleXrwmA0zEfzyZ3CdHpJdvORmIbcIy6iyE M2DSe0i2Rvl4LOpT5JmqPShX7HkSHai0uD/jrSp5FGXPTBau97UThytdhPJfkxE1Ub eTKAIUtr2edbPEYRbVHswi/NOIJ7yJ/Sg730r+qc= From: paulmck@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" , Bart Van Assche , Christoph Hellwig , Hannes Reinecke , Johannes Thumshirn , Shane M Seymour , "Martin K . Petersen" Subject: [PATCH tip/core/rcu 01/10] rcu: Upgrade rcu_swap_protected() to rcu_replace() Date: Tue, 22 Oct 2019 12:12:06 -0700 Message-Id: <20191022191215.25781-1-paulmck@kernel.org> X-Mailer: git-send-email 2.9.5 In-Reply-To: <20191022191136.GA25627@paulmck-ThinkPad-P72> References: <20191022191136.GA25627@paulmck-ThinkPad-P72> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" Although the rcu_swap_protected() macro follows the example of swap(), the interactions with RCU make its update of its argument somewhat counter-intuitive. This commit therefore introduces an rcu_replace() that returns the old value of the RCU pointer instead of doing the argument update. Once all the uses of rcu_swap_protected() are updated to instead use rcu_replace(), rcu_swap_protected() will be removed. Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/ Reported-by: Linus Torvalds [ paulmck: From rcu_replace() to rcu_replace_pointer() per Ingo Molnar. ] Signed-off-by: Paul E. McKenney Cc: Bart Van Assche Cc: Christoph Hellwig Cc: Hannes Reinecke Cc: Johannes Thumshirn Cc: Shane M Seymour Cc: Martin K. Petersen --- include/linux/rcupdate.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 75a2ede..185dd97 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -383,6 +383,24 @@ do { \ } while (0) /** + * rcu_replace_pointer() - replace an RCU pointer, returning its old value + * @rcu_ptr: RCU pointer, whose old value is returned + * @ptr: regular pointer + * @c: the lockdep conditions under which the dereference will take place + * + * Perform a replacement, where @rcu_ptr is an RCU-annotated + * pointer and @c is the lockdep argument that is passed to the + * rcu_dereference_protected() call used to read that pointer. The old + * value of @rcu_ptr is returned, and @rcu_ptr is set to @ptr. + */ +#define rcu_replace_pointer(rcu_ptr, ptr, c) \ +({ \ + typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c)); \ + rcu_assign_pointer((rcu_ptr), (ptr)); \ + __tmp; \ +}) + +/** * rcu_swap_protected() - swap an RCU and a regular pointer * @rcu_ptr: RCU pointer * @ptr: regular pointer -- 2.9.5