From patchwork Thu Jun 15 18:10:03 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: SeongJae Park X-Patchwork-Id: 13281644 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 DC27EEB64DD for ; Thu, 15 Jun 2023 18:10:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238201AbjFOSKU (ORCPT ); Thu, 15 Jun 2023 14:10:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32976 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239403AbjFOSKN (ORCPT ); Thu, 15 Jun 2023 14:10:13 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B4CDD295B; Thu, 15 Jun 2023 11:10:12 -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 51D8F61B53; Thu, 15 Jun 2023 18:10:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 31B7DC433CA; Thu, 15 Jun 2023 18:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686852611; bh=LmZp49bujap0FTIZFNAjgmpNWjLBvfyY95sutmfr3+o=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I0z65ADiAyCKOR5m6JF1PbHdbNM4ZmghQ5OQ4yv+XKhkevdpcC/ZohV0VrPfJf9pS cpWNYWx/mCgQYAtQvH453C8EsIKCD812AlfSG06/IWxk83+ZcnkP6vOS3WKGxVXeny QQ6agvN4Mx5e05DClpoq2uACw7grNLMcKj+ubI1cVCrBOsZ/TF9hioKzc16IelEDws 1FLeKO+irNBu1zMl0dtL4Re4406jhXNOZrc6XvGx3jTOV1+KaDq3fiVoF67cYDPA+K BP9JVFHkq35qBwLCE0DRmkIdanrbxvb5oUkQubgmdnX1VrFzSXJNBbYTW7HGwNZVXQ vEcQ4o6XC8kQw== From: SeongJae Park To: paulmck@kernel.org Cc: SeongJae Park , joel@joelfernandes.org, mmpgouride@gmail.com, corbet@lwn.net, rcu@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3 2/3] Docs/RCU/rculist_nulls: Fix hlist_[nulls]_head field names of 'obj' Date: Thu, 15 Jun 2023 18:10:03 +0000 Message-Id: <20230615181004.86850-3-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20230615181004.86850-1-sj@kernel.org> References: <20230615181004.86850-1-sj@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org 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 --- 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 4b66e2fd2fb5..a24783ebc5df 100644 --- a/Documentation/RCU/rculist_nulls.rst +++ b/Documentation/RCU/rculist_nulls.rst @@ -63,7 +63,7 @@ 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; @@ -75,7 +75,7 @@ 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; @@ -95,7 +95,7 @@ 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 @@ -163,7 +163,7 @@ 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();