From patchwork Mon Jul 17 18:03:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 13316160 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 310EDC001E0 for ; Mon, 17 Jul 2023 18:03:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229999AbjGQSD0 (ORCPT ); Mon, 17 Jul 2023 14:03:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229970AbjGQSDV (ORCPT ); Mon, 17 Jul 2023 14:03:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D49B499; Mon, 17 Jul 2023 11:03:20 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AA8A9611C5; Mon, 17 Jul 2023 18:03:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E07CAC4339A; Mon, 17 Jul 2023 18:03:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689616998; bh=vEUUOY6M/3b2MdG2PW8TiiGilUJqe947oj/T9vFTNTA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dwsvUF/M6y1htH9x4F8FD9RJ7dMM3iqjK0L9G/KO/bHFbfAbvKW9LQqgdffTCkrJ8 Q3VAWs2tJvzYG01qCc+I0khfxeLsX5IXuA1qB7E7B6bmN6KzPvg0NDwchVgnJZIkRt l/BgTtbHEtZ8VzJoDXONq4GP1/9sdbeAh16Ap3IUrKuqUoEdH5IIJkkIX1TXbu5hZI ZMocGgOmJXnGa8S6m/1xMih1P4I3vb6g6tBoxrHzFJD1HGwLxm8KgklhyGYt0jh8x3 PoBhOvFNITxVPY0ovU5TqzlWXzTrJ9FCy1Vy3qu9PymxoGgX6Z0t1iYAQmHbcobG8s ZyVrbtuztfxPw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 441F6CE092F; Mon, 17 Jul 2023 11:03:18 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, Alan Huang , "Paul E . McKenney" Subject: [PATCH rcu 6/6] rcu: Use WRITE_ONCE() for assignments to ->next for rculist_nulls Date: Mon, 17 Jul 2023 11:03:17 -0700 Message-Id: <20230717180317.1097590-6-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <6127192c-da9b-4599-9738-6e8f92e6c75c@paulmck-laptop> References: <6127192c-da9b-4599-9738-6e8f92e6c75c@paulmck-laptop> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: Alan Huang When the objects managed by rculist_nulls are allocated with SLAB_TYPESAFE_BY_RCU, old readers may still hold references to an object even though it is just now being added, which means the modification of ->next is visible to readers. This patch therefore uses WRITE_ONCE() for assignments to ->next. Signed-off-by: Alan Huang Signed-off-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google) --- include/linux/rculist_nulls.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/rculist_nulls.h b/include/linux/rculist_nulls.h index ba4c00dd8005..89186c499dd4 100644 --- a/include/linux/rculist_nulls.h +++ b/include/linux/rculist_nulls.h @@ -101,7 +101,7 @@ static inline void hlist_nulls_add_head_rcu(struct hlist_nulls_node *n, { struct hlist_nulls_node *first = h->first; - n->next = first; + WRITE_ONCE(n->next, first); WRITE_ONCE(n->pprev, &h->first); rcu_assign_pointer(hlist_nulls_first_rcu(h), n); if (!is_a_nulls(first)) @@ -137,7 +137,7 @@ static inline void hlist_nulls_add_tail_rcu(struct hlist_nulls_node *n, last = i; if (last) { - n->next = last->next; + WRITE_ONCE(n->next, last->next); n->pprev = &last->next; rcu_assign_pointer(hlist_nulls_next_rcu(last), n); } else {