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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 6EDA7C2B9F4 for ; Mon, 28 Jun 2021 15:58:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 43EB9619F1 for ; Mon, 28 Jun 2021 15:58:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232103AbhF1QA2 (ORCPT ); Mon, 28 Jun 2021 12:00:28 -0400 Received: from mail.kernel.org ([198.145.29.99]:34350 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230163AbhF1QA1 (ORCPT ); Mon, 28 Jun 2021 12:00:27 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3F5FD61A0F; Mon, 28 Jun 2021 15:58:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624895882; bh=csP55REVlUAszW4MM0vqV/RVMhEoLkY4GQk44xF0Zb4=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=hwInxAlGUv+JI7nc/C7vs+08Ff7D6oZT6QjWfoZaGFRFjpk5y+H4scf8qnBSk4wwv g+LZoaBcRcOGoyEsshQAagPv6XFLoIAosy9vSA2Hnz5c2RJae51IdJbPNgEWAZUi8R pp8/rY2Y9un7Rog1ra3zgjxbHHI35B5MCum+pBhsTCYYX51iQe2qhPw+jKQCiWCCh0 mkvz0tJ58SOyFaWfDx4aYRTZtfajPfZbAylsKTw7H4KLI2mzh8UlPVqnWNQ0Pqx111 TQGqYJj9ZlNZ5dA/okKOTfmOD5NPmZnLML7SrlwI44KYQNm8N04KI3FF8nOQMXl0Iq uijBm5Ffq2B0A== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 14C9E5C065A; Mon, 28 Jun 2021 08:58:02 -0700 (PDT) Date: Mon, 28 Jun 2021 08:58:02 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: LKML , Daniel Bristot de Oliveira , Ingo Molnar Subject: Re: [PATCH] tracing: Have osnoise_main() add a quiescent state for task rcu Message-ID: <20210628155802.GH4397@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210628114953.6dc06a91@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210628114953.6dc06a91@oasis.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 28, 2021 at 11:49:53AM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" > > ftracetest triggered: > > INFO: rcu_tasks detected stalls on tasks: > 00000000b92b832d: .. nvcsw: 1/1 holdout: 1 idle_cpu: -1/7 > task:osnoise/7 state:R running task stack: 0 pid: 2133 ppid: 2 flags:0x00004000 > Call Trace: > ? asm_sysvec_apic_timer_interrupt+0x12/0x20 > ? asm_sysvec_apic_timer_interrupt+0x12/0x20 > ? trace_hardirqs_on+0x2b/0xe0 > ? asm_sysvec_apic_timer_interrupt+0x12/0x20 > ? trace_clock_local+0xc/0x20 > ? osnoise_main+0x10e/0x450 > ? trace_softirq_entry_callback+0x50/0x50 > ? kthread+0x153/0x170 > ? __kthread_bind_mask+0x60/0x60 > ? ret_from_fork+0x22/0x30 > > While running osnoise tracer with other tracers that rely on > synchronize_rcu_tasks(), where that just hung. > > The reason is that osnoise_main() never schedules out if the interval > is less than 1, and this will cause synchronize_rcu_tasks() to never > return. > > Fixes: bce29ac9ce0bb ("trace: Add osnoise tracer") > Signed-off-by: Steven Rostedt (VMware) That looks like something I would do! Acked-by: Paul E. McKenney > --- > kernel/trace/trace_osnoise.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c > index 38aa5e208ffd..556d530af805 100644 > --- a/kernel/trace/trace_osnoise.c > +++ b/kernel/trace/trace_osnoise.c > @@ -1216,8 +1216,11 @@ static int osnoise_main(void *data) > * differently from hwlat_detector, the osnoise tracer can run > * without a pause because preemption is on. > */ > - if (interval < 1) > + if (interval < 1) { > + /* Let synchronize_rcu_tasks() make progress */ > + cond_resched_tasks_rcu_qs(); > continue; > + } > > if (msleep_interruptible(interval)) > break; > -- > 2.29.2 >