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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no 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 7515EC2BA83 for ; Wed, 12 Feb 2020 15:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F6B421739 for ; Wed, 12 Feb 2020 15:14:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728446AbgBLPOS (ORCPT ); Wed, 12 Feb 2020 10:14:18 -0500 Received: from mail.kernel.org ([198.145.29.99]:36656 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727519AbgBLPOS (ORCPT ); Wed, 12 Feb 2020 10:14:18 -0500 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 D93FA206D7; Wed, 12 Feb 2020 15:14:16 +0000 (UTC) Date: Wed, 12 Feb 2020 10:14:15 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, mingo@kernel.org, joel@joelfernandes.org, gregkh@linuxfoundation.org, gustavo@embeddedor.com, tglx@linutronix.de, paulmck@kernel.org, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com Subject: Re: [PATCH 4/8] sched,rcu,tracing: Mark preempt_count_{add,sub}() notrace Message-ID: <20200212101415.3615d66c@gandalf.local.home> In-Reply-To: <20200212150211.GS14897@hirez.programming.kicks-ass.net> References: <20200212093210.468391728@infradead.org> <20200212094107.838108888@infradead.org> <20200212092417.04c3da8c@gandalf.local.home> <20200212150211.GS14897@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 Wed, 12 Feb 2020 16:02:11 +0100 Peter Zijlstra wrote: > On Wed, Feb 12, 2020 at 09:24:17AM -0500, Steven Rostedt wrote: > > On Wed, 12 Feb 2020 10:32:14 +0100 > > Peter Zijlstra wrote: > > > > > Because of the requirement that no tracing happens until after we've > > > incremented preempt_count, see nmi_enter() / trace_rcu_enter(), mark > > > these functions as notrace. > > > > I actually depend on these function being traced. > > Why? They already have a tracepoint inside. Only when enabled. > > > We do have > > "preempt_enable_notrace()" and "preempt_disable_notrace()" for places > > that shouldn't be traced. Can't we use those? (or simply > > __preempt_count_add()) in the nmi_enter() code instead? (perhaps create > > a preempt_count_add_notrace()). > > My initial patch has __preempt_count_add/sub() in, but then I figured > someone would go complain the tracepoint would go missing. Fine, but what bug are you trying to fix? I haven't seen one mentioned yet. Function tracing has recursion protection, and tracing preempt_count in nmi_enter() causes no problems. What's the problem you are trying to solve? -- Steve