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=-15.4 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 18F93C433E6 for ; Sun, 7 Feb 2021 00:58:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DBC3664E8C for ; Sun, 7 Feb 2021 00:58:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229621AbhBGA5t (ORCPT ); Sat, 6 Feb 2021 19:57:49 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:12469 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229609AbhBGA5l (ORCPT ); Sat, 6 Feb 2021 19:57:41 -0500 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4DY9gY5Y9pzjKRb; Sun, 7 Feb 2021 08:55:37 +0800 (CST) Received: from [10.67.102.248] (10.67.102.248) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.498.0; Sun, 7 Feb 2021 08:56:51 +0800 Subject: Re: [PATCH] perf record: Fix continue profiling after draining the buffer To: Jiri Olsa , Namhyung Kim CC: , Alexey Budankov , Adrian Hunter , Alexander Shishkin , Mark Rutland , Arnaldo Carvalho de Melo , Ingo Molnar , Peter Zijlstra , linux-kernel , References: <20210205065001.23252-1-yangjihong1@huawei.com> From: Yang Jihong Message-ID: Date: Sun, 7 Feb 2021 08:56:41 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.248] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 2021/2/5 18:46, Jiri Olsa wrote: > On Fri, Feb 05, 2021 at 07:35:22PM +0900, Namhyung Kim wrote: >> Hello, >> >> On Fri, Feb 5, 2021 at 3:50 PM Yang Jihong wrote: >>> >>> commit da231338ec9c098707c8a1e4d8a50e2400e2fe17 uses eventfd to solve rare race >>> where the setting and checking of 'done' which add done_fd to pollfd. >>> When draining buffer, revents of done_fd is 0 and evlist__filter_pollfd >>> function returns a non-zero value. >>> As a result, perf record does not stop profiling. >>> >>> The following simple scenarios can trigger this condition: >>> >>> sleep 10 & >>> perf record -p $! >>> >>> After the sleep process exits, perf record should stop profiling and exit. >>> However, perf record keeps running. >>> >>> If pollfd revents contains only POLLERR or POLLHUP, >>> perf record indicates that buffer is draining and need to stop profiling. >>> Use fdarray_flag__nonfilterable to set done eventfd to nonfilterable objects, >>> so that evlist__filter_pollfd does not filter and check done eventfd. >>> >>> Fixes: da231338ec9c (perf record: Use an eventfd to wakeup when done) >>> Signed-off-by: Yang Jihong >>> --- >>> tools/perf/builtin-record.c | 2 +- >>> tools/perf/util/evlist.c | 8 ++++++++ >>> tools/perf/util/evlist.h | 4 ++++ >>> 3 files changed, 13 insertions(+), 1 deletion(-) >>> >>> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c >>> index fd3911650612..51e593e896ea 100644 >>> --- a/tools/perf/builtin-record.c >>> +++ b/tools/perf/builtin-record.c >>> @@ -1663,7 +1663,7 @@ static int __cmd_record(struct record *rec, int argc, const char **argv) >>> status = -1; >>> goto out_delete_session; >>> } >>> - err = evlist__add_pollfd(rec->evlist, done_fd); >>> + err = evlist__add_wakeup_eventfd(rec->evlist, done_fd); >>> if (err < 0) { >>> pr_err("Failed to add wakeup eventfd to poll list\n"); >>> status = err; >>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c >>> index 05363a7247c4..fea4c1e8010d 100644 >>> --- a/tools/perf/util/evlist.c >>> +++ b/tools/perf/util/evlist.c >>> @@ -572,6 +572,14 @@ int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask) >>> return perf_evlist__filter_pollfd(&evlist->core, revents_and_mask); >>> } >>> >>> +#ifdef HAVE_EVENTFD_SUPPORT >>> +int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd) >>> +{ >>> + return perf_evlist__add_pollfd(&evlist->core, fd, NULL, POLLIN, >>> + fdarray_flag__nonfilterable); >>> +} >>> +#endif >> >> Does it build when HAVE_EVENTFD_SUPPORT is not defined? > > yea, I was wondering the same.. but it's called only from > code within HAVE_EVENTFD_SUPPORT ifdef > > jirka > >> >> Thanks, >> Namhyung >> >> I have tested that if "eventfd" feature is removed from the FEATURE_TESTS_BASIC list in Makefile.feature, evlist__add_wakeup_eventfd will not be build. Modify as follows: diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature index 97cbfb31b762..d1603050764a 100644 --- a/tools/build/Makefile.feature +++ b/tools/build/Makefile.feature @@ -32,7 +32,6 @@ FEATURE_TESTS_BASIC := \ backtrace \ dwarf \ dwarf_getlocations \ - eventfd \ fortify-source \ sync-compare-and-swap \ get_current_dir_name \ Thanks, Yang >>> + >>> int evlist__poll(struct evlist *evlist, int timeout) >>> { >>> return perf_evlist__poll(&evlist->core, timeout); >>> diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h >>> index 1aae75895dea..6d4d62151bc8 100644 >>> --- a/tools/perf/util/evlist.h >>> +++ b/tools/perf/util/evlist.h >>> @@ -142,6 +142,10 @@ struct evsel *evlist__find_tracepoint_by_name(struct evlist *evlist, const char >>> int evlist__add_pollfd(struct evlist *evlist, int fd); >>> int evlist__filter_pollfd(struct evlist *evlist, short revents_and_mask); >>> >>> +#ifdef HAVE_EVENTFD_SUPPORT >>> +int evlist__add_wakeup_eventfd(struct evlist *evlist, int fd); >>> +#endif >>> + >>> int evlist__poll(struct evlist *evlist, int timeout); >>> >>> struct evsel *evlist__id2evsel(struct evlist *evlist, u64 id); >>> -- >>> 2.17.1 >>> >> > > . >