Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755923Ab3GQOti (ORCPT ); Wed, 17 Jul 2013 10:49:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:20734 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755695Ab3GQOtg (ORCPT ); Wed, 17 Jul 2013 10:49:36 -0400 Date: Wed, 17 Jul 2013 16:43:57 +0200 From: Oleg Nesterov To: Masami Hiramatsu Cc: Steven Rostedt , "zhangwei(Jovi)" , Jiri Olsa , Peter Zijlstra , Arnaldo Carvalho de Melo , Srikar Dronamraju , Frederic Weisbecker , Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/4] tracing: fix open/delete fixes Message-ID: <20130717144357.GA7358@redhat.com> References: <20130716185658.GA21167@redhat.com> <51E6032B.7070907@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51E6032B.7070907@hitachi.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1497 Lines: 40 On 07/17, Masami Hiramatsu wrote: > > At a glance, you're trying to change which operation will be > failed. Currently, user can not remove an event while someone > opens files which related to the event. And this approach > changes that the someone can remove the event even if the > files are opened (and read/write operation will be failed). > Am I understand correctly? Yes. Once again, I am still not sure and I am asking for your review. But to me this looks much better. To simplify the discussion, lets consider ftrace_enable_fops in particular. - Why should .open() block rmdir or unregister_uprobe_event? - Why do we need .open() at all? Whatever it can do to validate file/call/etc, .read/write can do the same. - If we kill .open/release, we do not need the nontrivial refcounting. Everything becomes simple, no need to keep the state "in between". We need event_mutex anyway (and note that other f_op's can also rely on other locks taken by trace_remove_event_call), the validation degrades to the trivial != NULL check. - This also simplifies trace_remove_event_call() paths, we know that once it takes event_mutex nobody can play with ftrace_event_file/ftrace_event_call we are going to free. Oleg. -- 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/