From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753036AbbIPUzA (ORCPT ); Wed, 16 Sep 2015 16:55:00 -0400 Received: from mail.kernel.org ([198.145.29.136]:36655 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752696AbbIPUy7 (ORCPT ); Wed, 16 Sep 2015 16:54:59 -0400 Date: Wed, 16 Sep 2015 17:54:54 -0300 From: Arnaldo Carvalho de Melo To: Mark Rutland Cc: linux-kernel@vger.kernel.org, Adrian Hunter , Ingo Molnar , Jiri Olsa , Peter Zijlstra Subject: Re: [PATCH] perf tools: session: avoid infinite loop Message-ID: <20150916205454.GI11551@kernel.org> References: <1442423929-12253-1-git-send-email-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1442423929-12253-1-git-send-email-mark.rutland@arm.com> X-Url: http://acmel.wordpress.com User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Em Wed, Sep 16, 2015 at 06:18:49PM +0100, Mark Rutland escreveu: > This has been observed to result in an exit-time hang when counting > rare/unschedulable events with perf record, and can be triggered > artificially with the script below: > > ---- > #!/bin/sh > printf "REPRO: launching perf\n"; > ./perf record -e software/config=9/ sleep 1 & > PERF_PID=$!; > sleep 0.002; > kill -2 $PERF_PID; > printf "REPRO: waiting for perf (%d) to exit...\n" "$PERF_PID"; > wait $PERF_PID; > printf "REPRO: perf exited\n"; > ---- So, I run it here, without this patch, and get: [root@zoo ~]# time ./repro.sh REPRO: launching perf REPRO: waiting for perf (766) to exit... [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.015 MB perf.data ] REPRO: perf exited real 0m1.060s user 0m0.018s sys 0m0.037s [root@zoo ~]# perf report --stdio Error: The perf.data file has no samples! # To display the perf.data header info, please use # --header/--header-only options. # [root@zoo ~]# perf evlist -v software/config=9/: type: 1, size: 112, config: 0x9, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1 [root@zoo ~]# What am I doing wrong? Trying to reproduce this before even looking at the patch :-) - Arnaldo > To avoid this, have __perf_session__process_events bail out early when > the file has no data (i.e. it has no events). > > Signed-off-by: Mark Rutland > Cc: Adrian Hunter > Cc: Arnaldo Carvalho de Melo > Cc: Ingo Molnar > Cc: Jiri Olsa > Cc: Peter Zijlstra > --- > tools/perf/util/session.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c > index 8a4537e..fc3f7c9 100644 > --- a/tools/perf/util/session.c > +++ b/tools/perf/util/session.c > @@ -1580,7 +1580,10 @@ static int __perf_session__process_events(struct perf_session *session, > file_offset = page_offset; > head = data_offset - page_offset; > > - if (data_size && (data_offset + data_size < file_size)) > + if (data_size == 0) > + goto out; > + > + if (data_offset + data_size < file_size) > file_size = data_offset + data_size; > > ui_progress__init(&prog, file_size, "Processing events..."); > -- > 1.9.1