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 77A90C2BAEE for ; Tue, 24 Mar 2020 15:37:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51D0920788 for ; Tue, 24 Mar 2020 15:37:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585064226; bh=tpwxeWGxCRW2edSpkeAxy800Wtnff4M8NvYgHsczp9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=E7iEXnoldXoNosjuGGzz9iqzy/K0ZJluEk/XY5dliANt4RVikigyafd+pXaQQildG 39lMycJzrjb+BdlKpUhLOXNoN8oZ2eRd6zBJYJ2j2s0W4vX9VrPk4chI69IB7dUmww kMYwRX5IO+ib9JbhNzVn4xSMBA8Kaunq3MdQrLtg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728385AbgCXPhF (ORCPT ); Tue, 24 Mar 2020 11:37:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:59660 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727216AbgCXPhD (ORCPT ); Tue, 24 Mar 2020 11:37:03 -0400 Received: from localhost.localdomain (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 6D131208C3; Tue, 24 Mar 2020 15:37:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585064223; bh=tpwxeWGxCRW2edSpkeAxy800Wtnff4M8NvYgHsczp9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GyC+w6VY0uSmE3ApXjwUpwX5/upSsRk4J8nsl07WC3p5tqV2i8jPvEAuKAlK6VLOA 6h8GgVtcwHzQNW0BOcMkN5/RquTjZm8tEQE+LAKF/f/euL8+wROPI3BYs1MoQnllOt 1IdzcQkQe3HLHySmnXBvNborGuNtuj9/B5bZ0U5g= From: Will Deacon To: linux-kernel@vger.kernel.org Cc: Will Deacon , Eric Dumazet , Jann Horn , Kees Cook , Maddie Stone , Marco Elver , "Paul E . McKenney" , Peter Zijlstra , Thomas Gleixner , kernel-team@android.com, kernel-hardening@lists.openwall.com Subject: [RFC PATCH 05/21] list: Comment missing WRITE_ONCE() in __list_del() Date: Tue, 24 Mar 2020 15:36:27 +0000 Message-Id: <20200324153643.15527-6-will@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200324153643.15527-1-will@kernel.org> References: <20200324153643.15527-1-will@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Although __list_del() is called from the RCU list implementation, it omits WRITE_ONCE() when updating the 'prev' pointer for the 'next' node. This is reasonable because concurrent RCU readers only access the 'next' pointers. Although it's obvious after reading the code, add a comment. Cc: Paul E. McKenney Cc: Peter Zijlstra Signed-off-by: Will Deacon --- include/linux/list.h | 1 + 1 file changed, 1 insertion(+) diff --git a/include/linux/list.h b/include/linux/list.h index 4d9f5f9ed1a8..ec1f780d1449 100644 --- a/include/linux/list.h +++ b/include/linux/list.h @@ -109,6 +109,7 @@ static inline void list_add_tail(struct list_head *new, struct list_head *head) */ static inline void __list_del(struct list_head * prev, struct list_head * next) { + /* RCU readers don't read the 'prev' pointer */ next->prev = prev; WRITE_ONCE(prev->next, next); } -- 2.20.1