From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753584Ab1H2NVL (ORCPT ); Mon, 29 Aug 2011 09:21:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:65492 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752794Ab1H2NVA (ORCPT ); Mon, 29 Aug 2011 09:21:00 -0400 Date: Mon, 29 Aug 2011 10:20:37 -0300 From: Arnaldo Carvalho de Melo To: Jiri Olsa Cc: Eric Dumazet , a.p.zijlstra@chello.nl, mingo@elte.hu, paulus@samba.org, linux-kernel@vger.kernel.org, Neil Horman Subject: Re: [PATCH] perf, tool, record: Fix the header generation for pipe Message-ID: <20110829132037.GB27261@ghostprotocols.net> References: <1314022997-9217-1-git-send-email-jolsa@redhat.com> <1314023913.2307.63.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> <20110822145210.GA8694@jolsa.brq.redhat.com> <1314028266.2307.93.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC> <20110822160713.GA10134@jolsa.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20110822160713.GA10134@jolsa.brq.redhat.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Mon, Aug 22, 2011 at 06:07:13PM +0200, Jiri Olsa escreveu: > On Mon, Aug 22, 2011 at 05:51:06PM +0200, Eric Dumazet wrote: > > Le lundi 22 août 2011 à 16:52 +0200, Jiri Olsa a écrit : > > > - fd is always file.. the descriptor, which might be pipe, is in output_fd variable > > > but, maybe the die call is not necessary.. this should not fail > > > - the record_file function is called only on debugfs or procfs files: > > > events/header_page > > > events/header_event > > > events/**/format > > > printk_formats > > > /proc/kallsyms > > > so I think I need to read the whole file as in current code. > > You read the file twice. Is it the right fix ? > > Once to compute the length to be able to write the output header, once > > to process the content. > > Are you sure length cannot change between the two phases ? > > /proc/kallsyms can definitely change when a module is loaded. > Right, better to store it to a temp file as you suggest, so we have > consistent view.. I'll prepare new patch. Hi Jiri, any news here? I just stumbled in this bug while testing Neil's net_dropmonitor script :-\ - Arnaldo