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=-8.8 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_SANE_1 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 41DBDC43331 for ; Mon, 30 Mar 2020 23:07:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 11C6620784 for ; Mon, 30 Mar 2020 23:07:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585609675; bh=4AVexlNiYtLyPvD8KLzOZUsgxdPsZ/3OqrKRBK5t78U=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=WnFrktabcUY0ve1uBMG0khZWiACo79TrCRkp/0b0WHZOzCSoE1ntKdTEMkDbIfRCR snYNMx3e+C/jC8jSfNHe4sgqK7HTesYU2mYsO3ROfku6wINofRQ9hnl7RsMWyh/A6p /e41p3Vi+di94RtsIkH9hFOOtYU2sLEBmK/Ew3B8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730018AbgC3XHy (ORCPT ); Mon, 30 Mar 2020 19:07:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:60484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729024AbgC3XHw (ORCPT ); Mon, 30 Mar 2020 19:07:52 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6516420771; Mon, 30 Mar 2020 23:07:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585609672; bh=4AVexlNiYtLyPvD8KLzOZUsgxdPsZ/3OqrKRBK5t78U=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=eaMgIeH63FPjbwbmlPJ1EDvOTFm3tqCkT0ss3Y+WINaDPNQ/I4KjnasBeJbiDOt2L 5MGtBK1edC6BncMz8rT8XPOqspWxPMHbLCCJF+s2hhVMeB1/VazpACz3WjycFJQy2X c2AXDCapRXA5Sjy7/HLSbURBVhd4l+B3/Wh9AUd8= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 3F4403523140; Mon, 30 Mar 2020 16:07:52 -0700 (PDT) Date: Mon, 30 Mar 2020 16:07:52 -0700 From: "Paul E. McKenney" To: Will Deacon Cc: linux-kernel@vger.kernel.org, Eric Dumazet , Jann Horn , Kees Cook , Maddie Stone , Marco Elver , Peter Zijlstra , Thomas Gleixner , kernel-team@android.com, kernel-hardening@lists.openwall.com Subject: Re: [RFC PATCH 02/21] list: Remove hlist_nulls_unhashed_lockless() Message-ID: <20200330230752.GY19865@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200324153643.15527-1-will@kernel.org> <20200324153643.15527-3-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200324153643.15527-3-will@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 24, 2020 at 03:36:24PM +0000, Will Deacon wrote: > Commit 02b99b38f3d9 ("rcu: Add a hlist_nulls_unhashed_lockless() function") > introduced the (as yet unused) hlist_nulls_unhashed_lockless() function > to avoid KCSAN reports when an RCU reader checks the 'hashed' status > of an 'hlist_nulls' concurrently undergoing modification. > > Remove the unused function and add a READ_ONCE() to hlist_nulls_unhashed(), > just like we do already for hlist_nulls_empty(). > > Cc: Paul E. McKenney > Cc: Peter Zijlstra > Signed-off-by: Will Deacon Well, I guess that the added docbook comment might be seen as worthwhile. Acked-by: Paul E. McKenney > --- > include/linux/list_nulls.h | 14 -------------- > 1 file changed, 14 deletions(-) > > diff --git a/include/linux/list_nulls.h b/include/linux/list_nulls.h > index fa6e8471bd22..3a9ff01e9a11 100644 > --- a/include/linux/list_nulls.h > +++ b/include/linux/list_nulls.h > @@ -65,20 +65,6 @@ static inline unsigned long get_nulls_value(const struct hlist_nulls_node *ptr) > * but hlist_nulls_del() does not. > */ > static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h) > -{ > - return !h->pprev; > -} > - > -/** > - * hlist_nulls_unhashed_lockless - Has node been removed and reinitialized? > - * @h: Node to be checked > - * > - * Not that not all removal functions will leave a node in unhashed state. > - * For example, hlist_del_init_rcu() leaves the node in unhashed state, > - * but hlist_nulls_del() does not. Unlike hlist_nulls_unhashed(), this > - * function may be used locklessly. > - */ > -static inline int hlist_nulls_unhashed_lockless(const struct hlist_nulls_node *h) > { > return !READ_ONCE(h->pprev); > } > -- > 2.20.1 >