From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753745AbdBJSFA (ORCPT ); Fri, 10 Feb 2017 13:05:00 -0500 Received: from mail.kernel.org ([198.145.29.136]:57122 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751802AbdBJSEj (ORCPT ); Fri, 10 Feb 2017 13:04:39 -0500 Date: Fri, 10 Feb 2017 19:39:49 +0200 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , David Miller Subject: [PATCH] hlist_add_tail_rcu disable sparse warning Message-ID: <1486748308-16653-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mailer: git-send-email 2.8.0.287.g0deeb61 X-Mutt-Fcc: =sent Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org sparse is unhappy about this code in hlist_add_tail_rcu: struct hlist_node *i, *last = NULL; for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i)) last = i; This is because hlist_next_rcu and hlist_next_rcu return __rcu pointers. It's a false positive - it's a write side primitive and so does not need to be called in a read side critical section. The following trivial patch disables the warning without changing the behaviour in any way. Note: __hlist_for_each_rcu would also remove the warning but it would be confusing since it calls rcu_derefence and is designed to run in the rcu read side critical section. Signed-off-by: Michael S. Tsirkin --- changes since RFC added commit log text to explain why don't we use __hlist_for_each_rcu include/linux/rculist.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/rculist.h b/include/linux/rculist.h index 4f7a956..bf578e8 100644 --- a/include/linux/rculist.h +++ b/include/linux/rculist.h @@ -509,7 +509,7 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n, { struct hlist_node *i, *last = NULL; - for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i)) + for (i = h->first; i; i = i->next) last = i; if (last) { -- MST