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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 5DAA6C43387 for ; Mon, 7 Jan 2019 09:05:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3663C2089F for ; Mon, 7 Jan 2019 09:05:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726835AbfAGJF0 (ORCPT ); Mon, 7 Jan 2019 04:05:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45200 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726601AbfAGJF0 (ORCPT ); Mon, 7 Jan 2019 04:05:26 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4300488E63; Mon, 7 Jan 2019 09:05:25 +0000 (UTC) Received: from krava (unknown [10.43.17.222]) by smtp.corp.redhat.com (Postfix) with SMTP id 08F5619743; Mon, 7 Jan 2019 09:05:22 +0000 (UTC) Date: Mon, 7 Jan 2019 10:05:22 +0100 From: Jiri Olsa To: Jin Yao 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 Subject: Re: [PATCH v2] Poll for monitored tasks being alive in fork mode Message-ID: <20190107090522.GA3383@krava> References: <1546822850-30649-1-git-send-email-yao.jin@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1546822850-30649-1-git-send-email-yao.jin@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Mon, 07 Jan 2019 09:05:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 07, 2019 at 09:00:50AM +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. > > v2: > --- > There is a potential race condition window, that is the > child_pid set with -1 and kill(-1, SIGTERM) may happen. > Jiri provides a simple method which stores the child_pid to > a local variable and check the local variable before kill(). > At least, we can avoid the kill(-1, SIGTERM) case. > > Signed-off-by: Jin Yao Reviewed-by: Jiri Olsa thanks, jirka > --- > tools/perf/builtin-stat.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c > index 63a3afc..bd5fb8e 100644 > --- a/tools/perf/builtin-stat.c > +++ b/tools/perf/builtin-stat.c > @@ -553,6 +553,15 @@ 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; > -- > 2.7.4 >