From patchwork Mon Jul 17 18:01:09 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: 13316151 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 DF3C7C001DE for ; Mon, 17 Jul 2023 18:01:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231250AbjGQSBT (ORCPT ); Mon, 17 Jul 2023 14:01:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32770 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230473AbjGQSBP (ORCPT ); Mon, 17 Jul 2023 14:01:15 -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 B38EB10C7; Mon, 17 Jul 2023 11:01:14 -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 56611611D4; Mon, 17 Jul 2023 18:01:13 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81611C433A9; Mon, 17 Jul 2023 18:01:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1689616872; bh=vMU/XgK+8/tyV/dKBByzpBIuwOGp8w97JCzbfLX+ZeY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=c9PPHQZiElIu01MSdWkSAMWPCHtk3+ULIDkRUtTy+2KSA4s50662trJuB+lhQlESi 6yImgsJSej19sc8OrrtpAlUsnkBaPz1Lu4p33NvTC3l5VhC3z0Ki2wN0lVlEueJ8BT y1HHhmXwV2PEB65Xzt/2EcMVOJKgD3DPo2PVMp8FBTt9IC0lVpubSaZoFJFkd0w1Td EEnAfNjZhqYu/iR1d/b/1+L4yXRRjULLr7IApvLNZzGwG8Hlo9iARtupoykSmcOSEM 5rhY5kUujZybVuRJa3BAr3coH8hkC0f25wkqyjJ2J21Z5oUK5y5erARLAtsm3XiimC 3duUJiqkDYsZw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id DD2EECE092F; Mon, 17 Jul 2023 11:01:11 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, SeongJae Park , "Paul E . McKenney" Subject: [PATCH rcu 6/7] Docs/RCU/rculist_nulls: Fix hlist_[nulls]_head field names of 'obj' Date: Mon, 17 Jul 2023 11:01:09 -0700 Message-Id: <20230717180110.1097362-6-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org From: SeongJae Park The example code snippets on rculist_nulls.rst are assuming 'obj' to have the 'hlist_head' or 'hlist_nulls_head' field named 'obj_node', but a sentence and some code snippets are wrongly calling 'obj->obj_node.next' as 'obj->obj_next', or 'obj->obj_node' as 'member'. Fix it. Signed-off-by: SeongJae Park Signed-off-by: Paul E. McKenney --- Documentation/RCU/rculist_nulls.rst | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/Documentation/RCU/rculist_nulls.rst b/Documentation/RCU/rculist_nulls.rst index 479cedfec446..1fb086066377 100644 --- a/Documentation/RCU/rculist_nulls.rst +++ b/Documentation/RCU/rculist_nulls.rst @@ -65,7 +65,7 @@ but a version with an additional memory barrier (smp_rmb()) struct hlist_node *node, *next; for (pos = rcu_dereference((head)->first); pos && ({ next = pos->next; smp_rmb(); prefetch(next); 1; }) && - ({ obj = hlist_entry(pos, typeof(*obj), member); 1; }); + ({ obj = hlist_entry(pos, typeof(*obj), obj_node); 1; }); pos = rcu_dereference(next)) if (obj->key == key) return obj; @@ -77,7 +77,7 @@ And note the traditional hlist_for_each_entry_rcu() misses this smp_rmb():: struct hlist_node *node; for (pos = rcu_dereference((head)->first); pos && ({ prefetch(pos->next); 1; }) && - ({ obj = hlist_entry(pos, typeof(*obj), member); 1; }); + ({ obj = hlist_entry(pos, typeof(*obj), obj_node); 1; }); pos = rcu_dereference(pos->next)) if (obj->key == key) return obj; @@ -97,7 +97,7 @@ Quoting Corey Minyard:: 2) Insertion algorithm ---------------------- -We need to make sure a reader cannot read the new 'obj->obj_next' value +We need to make sure a reader cannot read the new 'obj->obj_node.next' value and previous value of 'obj->key'. Otherwise, an item could be deleted from a chain, and inserted into another chain. If new chain was empty before the move, 'next' pointer is NULL, and lockless reader can not @@ -165,7 +165,7 @@ Note that using hlist_nulls means the type of 'obj_node' field of head = &table[slot]; begin: rcu_read_lock(); - hlist_nulls_for_each_entry_rcu(obj, node, head, member) { + hlist_nulls_for_each_entry_rcu(obj, node, head, obj_node) { if (obj->key == key) { if (!try_get_ref(obj)) { // might fail for free objects rcu_read_unlock();