From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E0DA7C43387 for ; Sun, 6 Jan 2019 14:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AA61A2085A for ; Sun, 6 Jan 2019 14:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726425AbfAFOCX (ORCPT ); Sun, 6 Jan 2019 09:02:23 -0500 Received: from mga05.intel.com ([192.55.52.43]:9169 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726336AbfAFOCX (ORCPT ); Sun, 6 Jan 2019 09:02:23 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 06 Jan 2019 06:02:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,447,1539673200"; d="scan'208";a="123702335" Received: from yjin15-mobl.ccr.corp.intel.com (HELO [10.254.215.129]) ([10.254.215.129]) by orsmga002.jf.intel.com with ESMTP; 06 Jan 2019 06:02:19 -0800 Subject: Re: [PATCH] perf stat: Poll for monitored tasks being alive in fork mode To: Jiri Olsa Cc: acme@kernel.org, jolsa@kernel.org, peterz@infradead.org, mingo@redhat.com, alexander.shishkin@linux.intel.com, Linux-kernel@vger.kernel.org, ak@linux.intel.com, kan.liang@intel.com, yao.jin@intel.com References: <1546568897-16123-1-git-send-email-yao.jin@linux.intel.com> <20190104125441.GF5481@krava> <20190106132509.GA31228@krava> From: "Jin, Yao" Message-ID: <3ccf2565-c271-1cba-e5dc-7c33302cf417@linux.intel.com> Date: Sun, 6 Jan 2019 22:02:18 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <20190106132509.GA31228@krava> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/6/2019 9:25 PM, Jiri Olsa wrote: > On Sat, Jan 05, 2019 at 11:16:40AM +0800, Jin, Yao wrote: >> >> >> On 1/4/2019 8:54 PM, Jiri Olsa wrote: >>> On Fri, Jan 04, 2019 at 10:28:17AM +0800, Jin Yao wrote: >>>> Following test shows the stat keeps running even if no longer >>>> task to monitor (mgen exits at ~5s). >>>> >>>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10 >>>> time counts unit events >>>> 1.000148916 1,308,365,864 cycles >>>> 2.000379171 1,297,269,875 cycles >>>> 3.000556719 1,297,187,078 cycles >>>> 4.000914241 761,261,827 cycles >>>> 5.001306091 cycles >>>> 6.001676881 cycles >>>> 7.002046336 cycles >>>> 8.002405651 cycles >>>> 9.002766625 cycles >>>> 10.001395827 cycles >>>> >>>> We'd better finish stat immediately if there's no longer task to >>>> monitor. >>>> >>>> After: >>>> >>>> perf stat -e cycles -p `pgrep mgen` -I1000 -- sleep 10 >>>> time counts unit events >>>> 1.000180062 1,236,592,661 cycles >>>> 2.000421539 1,223,733,572 cycles >>>> 3.000609910 1,297,047,663 cycles >>>> 4.000807545 1,297,215,816 cycles >>>> 5.001001578 1,297,208,032 cycles >>>> 6.001390345 582,343,659 cycles >>>> sleep: Terminated >>>> >>>> Now the stat exits immediately when the monitored tasks ends. >>>> >>>> Signed-off-by: Jin Yao >>>> --- >>>> tools/perf/builtin-stat.c | 7 +++++++ >>>> 1 file changed, 7 insertions(+) >>>> >>>> diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c >>>> index 63a3afc..71f3bc8 100644 >>>> --- a/tools/perf/builtin-stat.c >>>> +++ b/tools/perf/builtin-stat.c >>>> @@ -553,6 +553,13 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx) >>>> if (interval || timeout) { >>>> while (!waitpid(child_pid, &status, WNOHANG)) { >>>> + if (!is_target_alive(&target, >>>> + evsel_list->threads) && >>>> + (child_pid != -1)) { >>> >>> do we need that child_pid check? we just returned from waitpid >>> so we should be ok.. we just make the race window smaller >>> >>> could we just do: >>> >>> if (!is_target_alive(&target, evsel_list->threads)) { >>> kill(child_pid, SIGTERM); >>> break; >>> } >>> >> >> I think this code should be OK and I have tested yet. I have a question >> about the race condition, we really don't need a lock to protect the >> child_pid? >> >> skip_signal() >> { >> /* >> * render child_pid harmless >> * won't send SIGTERM to a random >> * process in case of race condition >> * and fast PID recycling >> */ >> child_pid = -1; >> } >> >> __run_perf_stat() >> { >> .... >> kill(child_pid, SIGTERM); >> } >> >> If child_pid is set by -1 in a small window between checking of child_pid >> and kill(), then kill(-1, SIGTERM) may happen. All processes except the kill >> process itself and init would receive SIGTERM. > > ah right, -1 is special.. however that can still happen also > in the orginal patch.. how about we do something like below > > jirka > > > --- > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index acfd48db52dd..c322cb271180 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -583,6 +583,14 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx) > > if (interval || timeout) { > while (!waitpid(child_pid, &status, WNOHANG)) { > + if (!is_target_alive(&target, evsel_list->threads)) { > + int pid = child_pid; > + > + if (pid != -1) > + kill(pid, SIGTERM); > + break; > + } > + > nanosleep(&ts, NULL); > if (timeout) > break; > Hi Jiri, I think your patch is good. At least, we can avoid the case of kill(-1, SIGTERM). BTW, you post this patch or I re-post it, both fine for me. :) Thanks Jin Yao