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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E8D3C433F5 for ; Mon, 16 May 2022 04:25:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236933AbiEPEZo (ORCPT ); Mon, 16 May 2022 00:25:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231135AbiEPEZj (ORCPT ); Mon, 16 May 2022 00:25:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4948419002; Sun, 15 May 2022 21:25:37 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C958460EF1; Mon, 16 May 2022 04:25:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 28EB7C385AA; Mon, 16 May 2022 04:25:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652675136; bh=wkoCQQWOI/OVKH1UsJ9YAUTlpusbXlznvf72YaWzN7k=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=CLuSkDkWjDqJUtOB4cZDaMTD7Mb1pLfHh7tcgD9Rxe7Uql/SJYAZFQlBbff7rGA97 QixQ0PcvXWBOek2r6CW++e2A7pQiAdnF48JwhR5GWROHk3Ti3mfs5kJlio9GO7evcK RbFKQXHH1qwaPS9lDtyF2BF+kCl/aCKCxBNW/+64QhMUpZEhNdyHXRzt1cw70f+gkI jZQdsupkXvCQ4tQXYeoEKObagASYqa5JPe34jpv5zJ4oYNqylSIchtnHNbwqR/Cxnk kPW+A/Zu+qwXM2WBjnKT0eIs1w3w3Mtlqeoav70v1rvy5Ku9khX49opmzcQkbrPw6h rjUj4++lTeEdA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id BBD275C0440; Sun, 15 May 2022 21:25:35 -0700 (PDT) Date: Sun, 15 May 2022 21:25:35 -0700 From: "Paul E. McKenney" To: Jiri Olsa Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Masami Hiramatsu , netdev@vger.kernel.org, bpf@vger.kernel.org, lkml , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Steven Rostedt Subject: Re: [PATCH bpf-next 1/2] cpuidle/rcu: Making arch_cpu_idle and rcu_idle_exit noinstr Message-ID: <20220516042535.GV1790663@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20220515203653.4039075-1-jolsa@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220515203653.4039075-1-jolsa@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 15, 2022 at 10:36:52PM +0200, Jiri Olsa wrote: > Making arch_cpu_idle and rcu_idle_exit noinstr. Both functions run > in rcu 'not watching' context and if there's tracer attached to > them, which uses rcu (e.g. kprobe multi interface) it will hit RCU > warning like: > > [ 3.017540] WARNING: suspicious RCU usage > ... > [ 3.018363] kprobe_multi_link_handler+0x68/0x1c0 > [ 3.018364] ? kprobe_multi_link_handler+0x3e/0x1c0 > [ 3.018366] ? arch_cpu_idle_dead+0x10/0x10 > [ 3.018367] ? arch_cpu_idle_dead+0x10/0x10 > [ 3.018371] fprobe_handler.part.0+0xab/0x150 > [ 3.018374] 0xffffffffa00080c8 > [ 3.018393] ? arch_cpu_idle+0x5/0x10 > [ 3.018398] arch_cpu_idle+0x5/0x10 > [ 3.018399] default_idle_call+0x59/0x90 > [ 3.018401] do_idle+0x1c3/0x1d0 > > The call path is following: > > default_idle_call > rcu_idle_enter > arch_cpu_idle > rcu_idle_exit > > The arch_cpu_idle and rcu_idle_exit are the only ones from above > path that are traceble and cause this problem on my setup. > > Signed-off-by: Jiri Olsa >From an RCU viewpoint: Reviewed-by: Paul E. McKenney [ I considered asking for an instrumentation_on() in rcu_idle_exit(), but there is no point given that local_irq_restore() isn't something you instrument anyway. ] > --- > arch/x86/kernel/process.c | 2 +- > kernel/rcu/tree.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c > index b370767f5b19..1345cb0124a6 100644 > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -720,7 +720,7 @@ void arch_cpu_idle_dead(void) > /* > * Called from the generic idle code. > */ > -void arch_cpu_idle(void) > +void noinstr arch_cpu_idle(void) > { > x86_idle(); > } > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index a4b8189455d5..20d529722f51 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -896,7 +896,7 @@ static void noinstr rcu_eqs_exit(bool user) > * If you add or remove a call to rcu_idle_exit(), be sure to test with > * CONFIG_RCU_EQS_DEBUG=y. > */ > -void rcu_idle_exit(void) > +void noinstr rcu_idle_exit(void) > { > unsigned long flags; > > -- > 2.35.3 >