From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754805Ab0ETNsu (ORCPT ); Thu, 20 May 2010 09:48:50 -0400 Received: from terminus.zytor.com ([198.137.202.10]:57096 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754721Ab0ETNsr (ORCPT ); Thu, 20 May 2010 09:48:47 -0400 Message-ID: <4BF53C1E.9040305@zytor.com> Date: Thu, 20 May 2010 06:41:50 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-2.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: Pekka Enberg CC: mingo@redhat.com, acme@redhat.com, paulus@samba.org, linux-kernel@vger.kernel.org, tzanussi@gmail.com, a.p.zijlstra@chello.nl, fweisbec@gmail.com, tglx@linutronix.de, mingo@elte.hu, linux-tip-commits@vger.kernel.org Subject: Re: [tip:perf/core] perf: Use read() instead of lseek() in trace_event_read.c:skip() References: <1273032130.6383.28.camel@tropicana> In-Reply-To: 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 On 05/20/2010 06:39 AM, Pekka Enberg wrote: > On Thu, May 20, 2010 at 3:54 PM, tip-bot for Tom Zanussi > wrote: >> Commit-ID: cbb5cf7ff6b298beacfe23db3386335b0b9c0a2d >> Gitweb: http://git.kernel.org/tip/cbb5cf7ff6b298beacfe23db3386335b0b9c0a2d >> Author: Tom Zanussi >> AuthorDate: Tue, 4 May 2010 23:02:10 -0500 >> Committer: Frederic Weisbecker >> CommitDate: Thu, 20 May 2010 08:37:17 +0200 >> >> perf: Use read() instead of lseek() in trace_event_read.c:skip() >> >> This is a small fix for a problem affecting live-mode, introduced >> recently: >> >> root@tropicana:~# perf trace rwtop >> perf trace started with Perl >> script /root/libexec/perf-core/scripts/perl/rwtop.pl >> >> Fatal: did not read header event >> >> commit d00a47cce569a3e660a8c9de5d57af28d6a9f0f7 added a skip() >> function to skip over e.g. header_page, but this doesn't work for >> live mode. This patch re-implements skip() to use read() instead of >> lseek() to fix that. > > Out of curiosity: why doesn't lseek() work and why can't we fix that? Presumably because we're reading from a nonseekable stream? -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.