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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 2E15FC43331 for ; Tue, 31 Mar 2020 11:39:17 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 7AE082073B for ; Tue, 31 Mar 2020 11:39:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="eaMgIeH6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AE082073B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18325-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 1217 invoked by uid 550); 31 Mar 2020 11:39:06 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 3920 invoked from network); 30 Mar 2020 23:08:04 -0000 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= 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> 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) 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 >