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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY,USER_AGENT_GIT 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 898AACA9EC7 for ; Sat, 2 Nov 2019 12:47:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 65DB1218AC for ; Sat, 2 Nov 2019 12:47:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726925AbfKBMr0 (ORCPT ); Sat, 2 Nov 2019 08:47:26 -0400 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:52006 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726229AbfKBMrZ (ORCPT ); Sat, 2 Nov 2019 08:47:25 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R911e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04391;MF=laijs@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0Th-eIi4_1572698841; Received: from localhost(mailfrom:laijs@linux.alibaba.com fp:SMTPD_---0Th-eIi4_1572698841) by smtp.aliyun-inc.com(127.0.0.1); Sat, 02 Nov 2019 20:47:22 +0800 From: Lai Jiangshan To: linux-kernel@vger.kernel.org Cc: Lai Jiangshan , "Paul E. McKenney" , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org Subject: [PATCH V2 6/7] rcu: clear the special.b.need_qs in rcu_note_context_switch() Date: Sat, 2 Nov 2019 12:45:58 +0000 Message-Id: <20191102124559.1135-7-laijs@linux.alibaba.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191102124559.1135-1-laijs@linux.alibaba.com> References: <20191102124559.1135-1-laijs@linux.alibaba.com> Reply-To: <20191101162109.GN20975@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It is better to clear the special.b.need_qs when it is replaced by special.b.blocked or it is really fulfill its goal in rcu_preempt_deferred_qs_irqrestore(). It makes rcu_qs() easier to be understood, and also prepares for the percpu rcu_preempt_depth patch, which reqires rcu_special bits to be clearred in irq-disable context. Signed-off-by: Lai Jiangshan --- kernel/rcu/tree_plugin.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index eb5906c55c8d..e16c3867d2ff 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -264,8 +264,6 @@ static void rcu_qs(void) __this_cpu_read(rcu_data.gp_seq), TPS("cpuqs")); __this_cpu_write(rcu_data.cpu_no_qs.b.norm, false); - barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */ - WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, false); } } @@ -297,6 +295,7 @@ void rcu_note_context_switch(bool preempt) /* Possibly blocking in an RCU read-side critical section. */ rnp = rdp->mynode; raw_spin_lock_rcu_node(rnp); + t->rcu_read_unlock_special.b.need_qs = false; t->rcu_read_unlock_special.b.blocked = true; t->rcu_blocked_node = rnp; -- 2.20.1