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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 F1599C2B9F4 for ; Mon, 28 Jun 2021 15:50:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D425A61A1D for ; Mon, 28 Jun 2021 15:50:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235990AbhF1Pw0 (ORCPT ); Mon, 28 Jun 2021 11:52:26 -0400 Received: from mail.kernel.org ([198.145.29.99]:60354 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235956AbhF1PwV (ORCPT ); Mon, 28 Jun 2021 11:52:21 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 88A38619BE; Mon, 28 Jun 2021 15:49:55 +0000 (UTC) Date: Mon, 28 Jun 2021 11:49:53 -0400 From: Steven Rostedt To: LKML Cc: Daniel Bristot de Oliveira , "Paul E. McKenney" , Ingo Molnar Subject: [PATCH] tracing: Have osnoise_main() add a quiescent state for task rcu Message-ID: <20210628114953.6dc06a91@oasis.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) --- 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