Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753478Ab3GHCg5 (ORCPT ); Sun, 7 Jul 2013 22:36:57 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:39267 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753375Ab3GHCgz (ORCPT ); Sun, 7 Jul 2013 22:36:55 -0400 Message-ID: <51DA25BF.6000701@hitachi.com> Date: Mon, 08 Jul 2013 11:36:47 +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 , linux-kernel@vger.kernel.org, "zhangwei(Jovi)" , Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , Srikar Dronamraju , Frederic Weisbecker , Ingo Molnar , Andrew Morton Subject: Re: [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probe event files are open References: <20130704033347.807661713@goodmis.org> <20130704034038.819592356@goodmis.org> <51D56E74.3090404@hitachi.com> <20130704184813.GA2695@redhat.com> <51D6351A.2000206@hitachi.com> <20130705172655.GA18576@redhat.com> In-Reply-To: <20130705172655.GA18576@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2240 Lines: 75 (2013/07/06 2:26), Oleg Nesterov wrote: > On 07/05, Masami Hiramatsu wrote: >> >> (2013/07/05 3:48), Oleg Nesterov wrote: >>> On 07/04, Masami Hiramatsu wrote: >>>> >>>> Actually disable_kprobe() doesn't ensure to finish the current running >>>> kprobe handlers. >>> >>> Yes. in fact disable_trace_probe(file != NULL) does, but perf doesn't. >> >> Ah, right. we did that. > > And thus we only need to synchronize kprobe_dispatcher()->kprobe_perf_func() > path. And afaics kprobe_perf_func() doesn't use anything which can be freed > by trace_remove_event_call? > >>>> OTOH, unregister_kprobe() waits for that. >>> >>> Yes. >>> >>> So I think we only need to move kfree(tp->call.print_fmt). > > OOPS. I was wrong. It seems that ->print_fmt is only for event/format ? > Then it is fine to kfree it right after trace_remove_event_call(). > >>> So the sequence should be: >>> >>> if (trace_remove_event_call(...)) >>> return; >>> >>> /* does synchronize_sched */ >>> unregister_kprobe(); >>> >>> kfree(everything); >>> >>> Agreed? >> >> If we can free everything after all, I'd like to do so. >> Hmm, but AFAICS, trace_remove_event_call() supposes that >> all event is disabled completely. > > Yes, but kprobe_trace_func() is really disabled? No, currently, doesn't. We need to fix that. (Perhaps, uprobes too.) >> A safe way is to wait rcu always right after disable_*probe >> in disable_trace_probe. If we have an unused link, we can >> free it after that. > > Aaaah... I am starting to understand... Even if kprobe_perf_func() > is fine, synchronize_sched() is calles _before_ disable_kprobe() > and thus it can't synchronize with the handlers which hit this probe > after we start synchronize_sched(). > > Did you mean this or I misssed something else? Right, thus perf path also need to be synchronized. Thank you, -- 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/