From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761489AbYD0Aox (ORCPT ); Sat, 26 Apr 2008 20:44:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753741AbYD0Aoq (ORCPT ); Sat, 26 Apr 2008 20:44:46 -0400 Received: from cantor2.suse.de ([195.135.220.15]:53090 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752800AbYD0Aop (ORCPT ); Sat, 26 Apr 2008 20:44:45 -0400 Date: Sat, 26 Apr 2008 17:36:45 -0700 From: Greg KH To: Mathieu Desnoyers Cc: Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: ftrace and debugfs weird interaction Message-ID: <20080427003645.GA19827@suse.de> References: <20080426185403.GA22522@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080426185403.GA22522@Krystal> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 26, 2008 at 02:54:03PM -0400, Mathieu Desnoyers wrote: > Hi, > > When trying to figure out what was going on with the sched tracer > "tracing_enabled" file (sched-devel.git tree), I fell on this strange > behavior : > > echo 1>tracing_enabled seems _not_ to send 1 to the tracing_ctrl_write > callback. However, sending garbage, e.g. echo s> tracing_enabled, > correctly sends the 's' character down the chain. echo 0>tracing_enabled > sometimes results in the callback not even being called. > > The debugfs file has been created with > > entry = debugfs_create_file("tracing_enabled", 0644, d_tracer, > &global_trace, &tracing_ctrl_fops); > if (!entry) > pr_warning("Could not create debugfs 'tracing_enabled' entry\n"); > > I wonder what kind of weird debugfs interaction we might have here ? I don't know. Are you sure your _fops is not getting called at all? How about using a "default" operation for such a simple file, like debugfs_create_bool() as that is all you care about for this kind of value? That should save you some code at the very least :) thanks, greg k-h