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 DFCB2CA9EC7 for ; Sat, 2 Nov 2019 12:47:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BDE01214AF for ; Sat, 2 Nov 2019 12:47:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726663AbfKBMrW (ORCPT ); Sat, 2 Nov 2019 08:47:22 -0400 Received: from out30-132.freemail.mail.aliyun.com ([115.124.30.132]:44642 "EHLO out30-132.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726380AbfKBMrV (ORCPT ); Sat, 2 Nov 2019 08:47:21 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R251e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=laijs@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0Th-eIhK_1572698838; Received: from localhost(mailfrom:laijs@linux.alibaba.com fp:SMTPD_---0Th-eIhK_1572698838) by smtp.aliyun-inc.com(127.0.0.1); Sat, 02 Nov 2019 20:47:19 +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 2/7] rcu: cleanup rcu_preempt_deferred_qs() Date: Sat, 2 Nov 2019 12:45:54 +0000 Message-Id: <20191102124559.1135-3-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 Don't need to set ->rcu_read_lock_nesting negative, irq-protected rcu_preempt_deferred_qs_irqrestore() doesn't expect ->rcu_read_lock_nesting to be negative to work, it even doesn't access to ->rcu_read_lock_nesting any more. It is true that NMI over rcu_preempt_deferred_qs_irqrestore() may access to ->rcu_read_lock_nesting, but it is still safe since rcu_read_unlock_special() can protect itself from NMI. Signed-off-by: Lai Jiangshan --- kernel/rcu/tree_plugin.h | 5 ----- 1 file changed, 5 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index aba5896d67e3..2fab8be2061f 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -552,16 +552,11 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t) static void rcu_preempt_deferred_qs(struct task_struct *t) { unsigned long flags; - bool couldrecurse = t->rcu_read_lock_nesting >= 0; if (!rcu_preempt_need_deferred_qs(t)) return; - if (couldrecurse) - t->rcu_read_lock_nesting -= RCU_NEST_BIAS; local_irq_save(flags); rcu_preempt_deferred_qs_irqrestore(t, flags); - if (couldrecurse) - t->rcu_read_lock_nesting += RCU_NEST_BIAS; } /* -- 2.20.1