Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756290Ab3HAOwB (ORCPT ); Thu, 1 Aug 2013 10:52:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48570 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754889Ab3HAOwA (ORCPT ); Thu, 1 Aug 2013 10:52:00 -0400 Date: Thu, 1 Aug 2013 16:46:22 +0200 From: Oleg Nesterov To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Masami Hiramatsu , "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 Message-ID: <20130801144622.GA15180@redhat.com> References: <20130704034038.819592356@goodmis.org> <1375300192.5418.17.camel@gandalf.local.home> <20130731204003.GA30188@redhat.com> <1375310548.5418.21.camel@gandalf.local.home> <1375322866.5418.46.camel@gandalf.local.home> <1375325414.5418.50.camel@gandalf.local.home> <20130801133455.GB8703@redhat.com> <1375366669.1152.23.camel@gandalf.local.home> <20130801143307.GA12031@redhat.com> <1375368339.1152.28.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1375368339.1152.28.camel@gandalf.local.home> 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: 1298 Lines: 43 On 08/01, Steven Rostedt wrote: > > On Thu, 2013-08-01 at 16:33 +0200, Oleg Nesterov wrote: > > On 08/01, Steven Rostedt wrote: > > > > > > On Thu, 2013-08-01 at 15:34 +0200, Oleg Nesterov wrote: > > > > > > > > > > __unregister_trace_probe(tp); > > > > > list_del(&tp->list) > > > > > unregister_probe_event(tp) <-- fails! > > > > > free_trace_probe(tp) > > > > > > > > Yes. But again, this doesn't explain why unregister_probe_event()-> > > > > __trace_remove_event_call() can't simply proceed and > > > > do ftrace_event_enable_disable() + remove_event_from_tracers(). > > > > > > The problem is with the soft disable. > > > > Exactly! This is another (also unlikely) race we need to prevent. > > > > Is there a race even with these patches? Sorry for confusion, > I don't see one. Neither me, but only with these changes. I meant that this is another reason why trace_remove_event_call() should fail and the caller should obviously abort in this case. > Or are you just saying that these patches fix that case too? Yes, sorry. 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/