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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 CF267C433DF for ; Sat, 27 Jun 2020 21:46:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8250206D7 for ; Sat, 27 Jun 2020 21:46:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593294392; bh=F3oRDiJxIGtXcCW5CIdMLvfO8YHc58JcaOd1gOgcwtg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=hW8/YEzJCvNKF8vpubu0a79iVE+d/h8JlBqrhg5GpS7RVIr8HN7gLNyS1y/LSdd7q 2dobkOCm6i8YK+4JNz8GgaeKt7pBZApOfYG3UIHi76G+6d75k0M9xtG/Ak5lg9iH7f 6wJqZippQkySaFzrOcsYfrfc5xyEu3EmC/ObAp2M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726069AbgF0Vqb (ORCPT ); Sat, 27 Jun 2020 17:46:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:56782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725907AbgF0Vqb (ORCPT ); Sat, 27 Jun 2020 17:46:31 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 19D52206D7; Sat, 27 Jun 2020 21:46:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593294390; bh=F3oRDiJxIGtXcCW5CIdMLvfO8YHc58JcaOd1gOgcwtg=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=wAzt260oInXC/o4Kk6eOxh8LSitHoSdBUCivK35C3smjvRGi5ImCI1v7tjBveJpVI e8saLa3UUiQQjUeXnub97h7LM6FYD00SzzY38gJlYlikPJDUK1fP4ZkZVUVaZA4hkV S5Mr94ySbi68duZyQ22U6YwUleyUm51VgBt55tVk= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 0180C3522FF8; Sat, 27 Jun 2020 14:46:29 -0700 (PDT) Date: Sat, 27 Jun 2020 14:46:29 -0700 From: "Paul E. McKenney" To: Andy Lutomirski Cc: Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , LKML , kernel-team Subject: Re: [PATCH tick-sched] Clarify "NOHZ: local_softirq_pending" warning Message-ID: <20200627214629.GH9247@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200626210506.GA27189@paulmck-ThinkPad-P72> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 27, 2020 at 02:02:15PM -0700, Andy Lutomirski wrote: > On Fri, Jun 26, 2020 at 2:05 PM Paul E. McKenney wrote: > > > > Currently, can_stop_idle_tick() prints "NOHZ: local_softirq_pending HH" > > (where "HH" is the hexadecimal softirq vector number) when one or more > > non-RCU softirq handlers are still enablded when checking to stop the > > scheduler-tick interrupt. This message is not as enlightening as one > > might hope, so this commit changes it to "NOHZ tick-stop error: Non-RCU > > local softirq work is pending, handler #HH. > > Thank you! It would be even better if it would explain *why* the > problem happened, but I suppose this code doesn't actually know. Glad to help! To your point, is it possible to bisect the appearance of this message, or is it as usual non-reproducible? (Hey, had to ask!) Thanx, Paul > --Andy > > > > > Reported-by: Andy Lutomirski > > Signed-off-by: Paul E. McKenney > > > > --- > > > > tick-sched.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c > > index f0199a4..349a25a 100644 > > --- a/kernel/time/tick-sched.c > > +++ b/kernel/time/tick-sched.c > > @@ -927,7 +927,7 @@ static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) > > > > if (ratelimit < 10 && > > (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { > > - pr_warn("NOHZ: local_softirq_pending %02x\n", > > + pr_warn("NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #%02x\n", > > (unsigned int) local_softirq_pending()); > > ratelimit++; > > }