Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754015Ab3FRCth (ORCPT ); Mon, 17 Jun 2013 22:49:37 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:36380 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752993Ab3FRCtg (ORCPT ); Mon, 17 Jun 2013 22:49:36 -0400 Message-ID: <51BFCAB8.20008@hitachi.com> Date: Tue, 18 Jun 2013 11:49:28 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 5.2; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Oleg Nesterov Cc: Steven Rostedt , Frederic Weisbecker , Ingo Molnar , Srikar Dronamraju , "zhangwei(Jovi)" , linux-kernel@vger.kernel.org, "yrl.pp-manager.tt@hitachi.com" Subject: Re: [PATCH 2/3] tracing/kprobes: Kill probe_enable_lock References: <20130616172149.GA8540@redhat.com> <51BE97C0.1070203@hitachi.com> <20130617151841.GA32267@redhat.com> In-Reply-To: <20130617151841.GA32267@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2045 Lines: 71 (2013/06/18 0:18), Oleg Nesterov wrote: > On 06/17, Masami Hiramatsu wrote: >> >> (2013/06/17 2:21), Oleg Nesterov wrote: >>> enable_trace_probe() and disable_trace_probe() should not worry about >>> serialization, the caller (perf_trace_init or __ftrace_set_clr_event) >>> holds event_mutex. >>> >>> They are also called by kprobe_trace_self_tests_init(), but this __init >>> function can't race with itself or trace_events.c >> >> Right, >> For safety, we should comment this at the caller side, > > Which caller do you mean? I meant the caller was kprobe_test_self_tests_init(). Since that function calls enable/disable_trace_probe() without holding event_mutex, we need to notice that (this is safe because there is no race) at the calling places :) Thank you, > > The patch adds > > /* > * This and enable_trace_probe/disable_trace_probe rely on event_mutex > * held by the caller, __ftrace_set_clr_event(). > */ > > above trace_probe_nr_files() but the next patch removes this function > with the comment... > > Will you agree with this patch if I add something like > > /* > * called by perf_trace_init() or __ftrace_set_clr_event() under event_mutex > */ > > above kprobe_register() ? Perhaps it makes sense to add > lockdep_assert_held(&event_mutex) into the body? > > And: > >> because >> those calls are the reason why I have introduced this lock. > > Please do not hesitate to nack this patch if you think that we should > keep probe_enable_lock for safety even if it is not currently needed. > In this case I'd suggest to move lock/unlock into kprobe_register() > but this is minor. > > Oleg. > > -- Masami HIRAMATSU IT Management Research Dept. Linux Technology Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/