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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 BF6EAC433DB for ; Tue, 26 Jan 2021 11:25:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 89D8822795 for ; Tue, 26 Jan 2021 11:25:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392359AbhAZLZ0 (ORCPT ); Tue, 26 Jan 2021 06:25:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390474AbhAZJVA (ORCPT ); Tue, 26 Jan 2021 04:21:00 -0500 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E850C061573 for ; Tue, 26 Jan 2021 01:20:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=Q9yE/oVgRydpOnLhnRRFpkqj6GKkbjfTgZQfYqeWzUc=; b=C3Cwtcpl27yjepgQnL3krYcAf0 vWQHfCts90VSL4frhf/kfITk3Dpjt9M4vfVJooEfkKLh/GHVrOClNNQ/s7MpLEMCYYk3uMeOYI5Yb +ExVFQ3lkmD8MhJ2ic1lX2kgSLT9adqCtKluK5MIszcBE/7ZsIVjW5Eq9df/AXLwyhlwykyR3/99y qOeOMIRWSbRAichrBdEtCAAkBYwgGzqcDTql3X40F3xtcsp8qlB3dROO6c57OmzHQB5VdkeBvFqW9 ClGdyxCoDAxpZMZF8QyYfPJy8NmHfESCAVXMxFRzSD9FlAiUQhJA7kjDnE+HhOhMXdu29tb9Lv7/R IHgBcwKA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1l4KWH-0005LY-1O; Tue, 26 Jan 2021 09:20:17 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id A02C73019CE; Tue, 26 Jan 2021 10:20:13 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 7D27A209C50F2; Tue, 26 Jan 2021 10:20:13 +0100 (CET) Date: Tue, 26 Jan 2021 10:20:13 +0100 From: Peter Zijlstra To: qiang.zhang@windriver.com Cc: valentin.schneider@arm.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/core: add rcu_read_lock/unlock() protection Message-ID: References: <20210126084651.32277-1-qiang.zhang@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210126084651.32277-1-qiang.zhang@windriver.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 26, 2021 at 04:46:51PM +0800, qiang.zhang@windriver.com wrote: > From: Zqiang > > Due to for_each_process_thread belongs to RCU read operation, > need to add rcu_read_lock/unlock() protection. > > Signed-off-by: Zqiang > --- > kernel/sched/core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 8c5481077c9c..c3f0103fdf53 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7738,6 +7738,7 @@ static void dump_rq_tasks(struct rq *rq, const char *loglvl) > lockdep_assert_held(&rq->lock); > > printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running); > + rcu_read_lock(); > for_each_process_thread(g, p) { > if (task_cpu(p) != cpu) > continue; > @@ -7747,6 +7748,7 @@ static void dump_rq_tasks(struct rq *rq, const char *loglvl) > > printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm); > } > + rcu_read_unlock(); We're in stop machine, with IRQs disabled, please explain how this can make any difference?