From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755161AbaGWGId (ORCPT ); Wed, 23 Jul 2014 02:08:33 -0400 Received: from mga01.intel.com ([192.55.52.88]:6094 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751143AbaGWGIc (ORCPT ); Wed, 23 Jul 2014 02:08:32 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,715,1400050800"; d="scan'208";a="565874332" Message-ID: <53CF5106.8080100@intel.com> Date: Wed, 23 Jul 2014 09:07:02 +0300 From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Arnaldo Carvalho de Melo CC: Peter Zijlstra , linux-kernel@vger.kernel.org, David Ahern , Frederic Weisbecker , Jiri Olsa , Namhyung Kim , Paul Mackerras , Stephane Eranian Subject: Re: [PATCH 01/52] perf tools: Fix jump label always changing during tracing References: <1406035081-14301-1-git-send-email-adrian.hunter@intel.com> <1406035081-14301-2-git-send-email-adrian.hunter@intel.com> <20140722140034.GE20303@kernel.org> In-Reply-To: <20140722140034.GE20303@kernel.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/22/2014 05:00 PM, Arnaldo Carvalho de Melo wrote: > Em Tue, Jul 22, 2014 at 04:17:10PM +0300, Adrian Hunter escreveu: >> Intel PT decoding walks the object code to reconstruct >> the trace. A jump label change during tracing causes >> decoding errors. >> >> The "Enable close-on-exec flag on perf file descriptor" >> patch caused there to be always a jump label change. >> >> It was found that using a per-cpu context instead of a >> per-thread context for the probe of the close-on-exec >> feature, made the problem go away. > > And it is ok for our purposes, as this code just needs to figure out if > PERF_FLAG_FD_CLOEXEC is present, but I wonder when this kind of thing > will hit again... Possibly > > Anyway, I'll take this patch. Thanks! > > - Arnaldo > >> Signed-off-by: Adrian Hunter >> --- >> tools/perf/util/cloexec.c | 9 +++++++-- >> 1 file changed, 7 insertions(+), 2 deletions(-) >> >> diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c >> index c5d05ec..6a37be5 100644 >> --- a/tools/perf/util/cloexec.c >> +++ b/tools/perf/util/cloexec.c >> @@ -1,3 +1,4 @@ >> +#include >> #include "util.h" >> #include "../perf.h" >> #include "cloexec.h" >> @@ -14,9 +15,13 @@ static int perf_flag_probe(void) >> }; >> int fd; >> int err; >> + int cpu = sched_getcpu(); >> + >> + if (cpu < 0) >> + cpu = 0; >> >> /* check cloexec flag */ >> - fd = sys_perf_event_open(&attr, 0, -1, -1, >> + fd = sys_perf_event_open(&attr, -1, cpu, -1, >> PERF_FLAG_FD_CLOEXEC); >> err = errno; >> >> @@ -30,7 +35,7 @@ static int perf_flag_probe(void) >> err, strerror(err)); >> >> /* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */ >> - fd = sys_perf_event_open(&attr, 0, -1, -1, 0); >> + fd = sys_perf_event_open(&attr, -1, cpu, -1, 0); >> err = errno; >> >> if (WARN_ONCE(fd < 0, >> -- >> 1.8.3.2 > >