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=ham 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 02F39CA9EC3 for ; Thu, 31 Oct 2019 10:08:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CAD1A2086D for ; Thu, 31 Oct 2019 10:08:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727450AbfJaKIw (ORCPT ); Thu, 31 Oct 2019 06:08:52 -0400 Received: from out4436.biz.mail.alibaba.com ([47.88.44.36]:61424 "EHLO out4436.biz.mail.alibaba.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727283AbfJaKIo (ORCPT ); Thu, 31 Oct 2019 06:08:44 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R191e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04420;MF=laijs@linux.alibaba.com;NM=1;PH=DS;RN=9;SR=0;TI=SMTPD_---0TgmBgRY_1572516511; Received: from localhost(mailfrom:laijs@linux.alibaba.com fp:SMTPD_---0TgmBgRY_1572516511) by smtp.aliyun-inc.com(127.0.0.1); Thu, 31 Oct 2019 18:08:32 +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 04/11] rcu: cleanup rcu_preempt_deferred_qs() Date: Thu, 31 Oct 2019 10:07:59 +0000 Message-Id: <20191031100806.1326-5-laijs@linux.alibaba.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191031100806.1326-1-laijs@linux.alibaba.com> References: <20191031100806.1326-1-laijs@linux.alibaba.com> 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 82595db04eec..9fe8138ed3c3 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -555,16 +555,11 @@ 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