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=-15.3 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,URIBL_BLOCKED, 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 51BDEC4332D for ; Thu, 18 Feb 2021 12:12:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E07A64EAD for ; Thu, 18 Feb 2021 12:12:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232430AbhBRMJn (ORCPT ); Thu, 18 Feb 2021 07:09:43 -0500 Received: from szxga05-in.huawei.com ([45.249.212.191]:12977 "EHLO szxga05-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230113AbhBRKjz (ORCPT ); Thu, 18 Feb 2021 05:39:55 -0500 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga05-in.huawei.com (SkyGuard) with ESMTP id 4Dh9cq66QtzjP6f; Thu, 18 Feb 2021 18:17:31 +0800 (CST) Received: from [10.67.102.248] (10.67.102.248) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.498.0; Thu, 18 Feb 2021 18:18:52 +0800 Subject: Re: [PATCH] perf record: Fix continue profiling after draining the buffer From: Yang Jihong 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> Message-ID: Date: Thu, 18 Feb 2021 18:18:46 +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: 8bit 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 2021/2/7 8:56, Yang Jihong wrote: > 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 >>>> >>> >> >> . >> Do have any other questions about this patch? Look forward to your review. Thanks, Yang