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 EF6FAC76186 for ; Tue, 30 Jul 2019 01:59:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C60AE2070B for ; Tue, 30 Jul 2019 01:59:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730776AbfG3B7r (ORCPT ); Mon, 29 Jul 2019 21:59:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:37076 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725864AbfG3B7r (ORCPT ); Mon, 29 Jul 2019 21:59:47 -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 5C65E206E0; Tue, 30 Jul 2019 01:59:45 +0000 (UTC) Date: Mon, 29 Jul 2019 21:59:43 -0400 From: Steven Rostedt To: Eiichi Tsukata Cc: Peter Zijlstra , Andy Lutomirski , Joel Fernandes , "Paul E. McKenney" , Thomas Gleixner , Ingo Molnar , Frederic Weisbecker , LKML Subject: Re: [PATCH] tracing: Prevent RCU EQS breakage in preemptirq events Message-ID: <20190729215943.63ff2081@oasis.local.home> In-Reply-To: References: <20190729010734.3352-1-devel@etsukata.com> <20190729102948.GY31381@hirez.programming.kicks-ass.net> 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 Tue, 30 Jul 2019 10:50:36 +0900 Eiichi Tsukata wrote: > > > > I think they already (try to) do that; see 'tracing_irq_cpu'. > > > > Or you mean something like this? > As for trace_hardirqs_off_caller: You missed what Peter said. > > diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c > index 4d8e99fdbbbe..d39478bcf0f2 100644 > --- a/kernel/trace/trace_preemptirq.c > +++ b/kernel/trace/trace_preemptirq.c > @@ -66,7 +66,7 @@ __visible void trace_hardirqs_off_caller(unsigned long caller_addr) > if (!this_cpu_read(tracing_irq_cpu)) { ^^^^^^^^^^^^^^^ The above makes this called only the first time we disable interrupts. > this_cpu_write(tracing_irq_cpu, 1); > tracer_hardirqs_off(CALLER_ADDR0, caller_addr); > - if (!in_nmi()) > + if (!in_nmi() && !irqs_disabled()) This would always be false. This function is always called with irqs_disabled()! So no, this is not what is meant. > trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); > } > > Or > > diff --git a/kernel/trace/trace_preemptirq.c b/kernel/trace/trace_preemptirq.c > index 4d8e99fdbbbe..e08c5c6ff2b3 100644 > --- a/kernel/trace/trace_preemptirq.c > +++ b/kernel/trace/trace_preemptirq.c > @@ -66,8 +66,6 @@ __visible void trace_hardirqs_off_caller(unsigned long caller_addr) > if (!this_cpu_read(tracing_irq_cpu)) { > this_cpu_write(tracing_irq_cpu, 1); > tracer_hardirqs_off(CALLER_ADDR0, caller_addr); > - if (!in_nmi()) > - trace_irq_disable_rcuidle(CALLER_ADDR0, caller_addr); And this just removes the tracepoint completely? -- Steve > } > > > As for trace_hardirqs_on_caller, it is called when IRQs off and CONTEXT_USER. > So even though we skipped the trace event if the previous state was already IRQs on, > we will fall into the same situation.