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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 A1A73C10F14 for ; Tue, 15 Oct 2019 10:51:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 76C6F2089C for ; Tue, 15 Oct 2019 10:51:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731557AbfJOKvE (ORCPT ); Tue, 15 Oct 2019 06:51:04 -0400 Received: from mx2.suse.de ([195.135.220.15]:39368 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731364AbfJOKvC (ORCPT ); Tue, 15 Oct 2019 06:51:02 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 6E6CBB4C2; Tue, 15 Oct 2019 10:51:00 +0000 (UTC) Date: Tue, 15 Oct 2019 12:50:59 +0200 (CEST) From: Miroslav Benes To: Petr Mladek cc: Steven Rostedt , jikos@kernel.org, joe.lawrence@redhat.com, jpoimboe@redhat.com, mingo@redhat.com, linux-kernel@vger.kernel.org, live-patching@vger.kernel.org Subject: Re: [PATCH v2] ftrace: Introduce PERMANENT ftrace_ops flag In-Reply-To: <20191015074540.bxehllisibls3kk7@pathway.suse.cz> Message-ID: References: <20191014105923.29607-1-mbenes@suse.cz> <20191014111719.141bd4fa@gandalf.local.home> <20191015074540.bxehllisibls3kk7@pathway.suse.cz> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 15 Oct 2019, Petr Mladek wrote: > On Mon 2019-10-14 11:17:19, Steven Rostedt wrote: > > On Mon, 14 Oct 2019 12:59:23 +0200 > > Miroslav Benes wrote: > > > > > int > > > ftrace_enable_sysctl(struct ctl_table *table, int write, > > > void __user *buffer, size_t *lenp, > > > @@ -6740,8 +6754,6 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, > > > if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled)) > > > goto out; > > > > > > - last_ftrace_enabled = !!ftrace_enabled; > > > - > > > if (ftrace_enabled) { > > > > > > /* we are starting ftrace again */ > > > @@ -6752,12 +6764,19 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, > > > ftrace_startup_sysctl(); > > > > > > } else { > > > + if (is_permanent_ops_registered()) { > > > + ftrace_enabled = last_ftrace_enabled; > > > > Although this is not incorrect, but may be somewhat confusing. > > > > At this location, last_ftrace_enabled is always true. > > > > I'm thinking this would be better to simply set it to false here. > > IMHO, we want to set ftrace_enabled = true here. > > It was set to "false" by writing to the sysfs file. But the change > gets rejected. ftrace will stay enabled. So, we should set > the value back to "true". That's correct. I can make it explicit as proposed. I just thought that 'ftrace_enabled = last_ftrace_enabled' was clear enough given Petr's explanation. > > > + ret = -EBUSY; > > > + goto out; > > > + } > > > + > > > /* stopping ftrace calls (just send to ftrace_stub) */ > > > ftrace_trace_function = ftrace_stub; > > > > > > ftrace_shutdown_sysctl(); > > > } > > > > > > + last_ftrace_enabled = !!ftrace_enabled; > > > out: > > > > And move the assignment of last_ftrace_enabled to after the "out:" > > label. > > This change might make sense anyway. But it is not strictly necessary > from my POV. If it stays before "out:" label, last_ftrace_enabled is set if and only if it has to be set. I think it is better, but I can, of course, move it in v3 if Steven prefers it. Thanks Miroslav