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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 363CEC7618B for ; Mon, 29 Jul 2019 15:21:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 10A1C216C8 for ; Mon, 29 Jul 2019 15:21:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728756AbfG2PVa (ORCPT ); Mon, 29 Jul 2019 11:21:30 -0400 Received: from mail.kernel.org ([198.145.29.99]:38196 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728023AbfG2PV3 (ORCPT ); Mon, 29 Jul 2019 11:21:29 -0400 Received: from gandalf.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 0B6052064A; Mon, 29 Jul 2019 15:21:27 +0000 (UTC) Date: Mon, 29 Jul 2019 11:21:26 -0400 From: Steven Rostedt To: Eiichi Tsukata Cc: joel@joelfernandes.org, paulmck@linux.vnet.ibm.com, tglx@linutronix.de, peterz@infradead.org, mingo@redhat.com, fweisbec@gmail.com, luto@amacapital.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] tracing: Prevent RCU EQS breakage in preemptirq events Message-ID: <20190729112126.6554b141@gandalf.local.home> In-Reply-To: <20190729010734.3352-1-devel@etsukata.com> References: <20190729010734.3352-1-devel@etsukata.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 29 Jul 2019 10:07:34 +0900 Eiichi Tsukata wrote: > If context tracking is enabled, causing page fault in preemptirq > irq_enable or irq_disable events triggers the following RCU EQS warning. > > Reproducer: > > // CONFIG_PREEMPTIRQ_EVENTS=y > // CONFIG_CONTEXT_TRACKING=y > // CONFIG_RCU_EQS_DEBUG=y > # echo 1 > events/preemptirq/irq_disable/enable > # echo 1 > options/userstacktrace So the problem is only with userstacktrace enabled? > } > diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c > index 4d8e99fdbbbe..031b51cb94d0 100644 > --- a/kernel/trace/trace_preemptirq.c > +++ b/kernel/trace/trace_preemptirq.c > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > #include "trace.h" > > #define CREATE_TRACE_POINTS > @@ -49,9 +50,14 @@ NOKPROBE_SYMBOL(trace_hardirqs_off); > > __visible void trace_hardirqs_on_caller(unsigned long caller_addr) > { > + enum ctx_state prev_state; > + > if (this_cpu_read(tracing_irq_cpu)) { > - if (!in_nmi()) > + if (!in_nmi()) { This is a very high fast path (for tracing irqs off and such). Instead of adding a check here for a case that is seldom used (userstacktrace and tracing irqs on/off). Move this to surround the userstack trace code. -- Steve > + prev_state = exception_enter(); > trace_irq_enable_rcuidle(CALLER_ADDR0, caller_addr); > + exception_exit(prev_state); > + } > tracer_hardirqs_on(CALLER_ADDR0, caller_addr); > this_cpu_write(tracing_irq_cpu, 0); > } > @@ -63,11 +69,16 @@ NOKPROBE_SYMBOL(trace_hardirqs_on_caller); > > __visible void trace_hardirqs_off_caller(unsigned long caller_addr) > { > + enum ctx_state prev_state; > + > if (!this_cpu_read(tracing_irq_cpu)) { > this_cpu_write(tracing_irq_cpu, 1); > tracer_hardirqs_off(CALLER_ADDR0, caller_addr); > - if (!in_nmi()) > + if (!in_nmi()) { > + prev_state = exception_enter(); > trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); > + exception_exit(prev_state); > + } > } > > lockdep_hardirqs_off(CALLER_ADDR0);