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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 12823C10F27 for ; Tue, 10 Mar 2020 18:32:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DDED7208C3 for ; Tue, 10 Mar 2020 18:32:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727601AbgCJSb6 (ORCPT ); Tue, 10 Mar 2020 14:31:58 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:34856 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727268AbgCJSb5 (ORCPT ); Tue, 10 Mar 2020 14:31:57 -0400 Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jBjfG-0001FW-W1; Tue, 10 Mar 2020 19:31:39 +0100 Received: by nanos.tec.linutronix.de (Postfix, from userid 1000) id 62A48104084; Tue, 10 Mar 2020 19:31:38 +0100 (CET) From: Thomas Gleixner To: Mathieu Desnoyers Cc: linux-kernel , Peter Zijlstra , rostedt , Masami Hiramatsu , Alexei Starovoitov , paulmck , "Joel Fernandes\, Google" , Frederic Weisbecker Subject: Re: Instrumentation and RCU In-Reply-To: <1666704263.23816.1583862003925.JavaMail.zimbra@efficios.com> References: <87mu8p797b.fsf@nanos.tec.linutronix.de> <1403546357.21810.1583779060302.JavaMail.zimbra@efficios.com> <871rq171ca.fsf@nanos.tec.linutronix.de> <1489283504.23399.1583852595008.JavaMail.zimbra@efficios.com> <87imjc5f6a.fsf@nanos.tec.linutronix.de> <1666704263.23816.1583862003925.JavaMail.zimbra@efficios.com> Date: Tue, 10 Mar 2020 19:31:38 +0100 Message-ID: <87d09k5aet.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Mathieu Desnoyers writes: > ----- On Mar 10, 2020, at 12:48 PM, Thomas Gleixner tglx@linutronix.de wrote: >> How do you "fix" that when you can't reach the tracepoint because you >> trip over a breakpoint and then while trying to fixup that stuff you hit >> another one? > > I may still be missing something, but if the fixup code (AFAIU the code performing > the out-of-line single-stepping of the original instruction) belongs to a section > hidden from instrumentation, it should not be an issue. Sure, but what guarantees that on the way there is nothing which might call into instrumentable code? Nothing, really. That's why I want the explicit sections which can be analyzed by tools. Humans (including me) are really bad at it was demonstrated several times. Thanks, tglx