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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8001EECAAD8 for ; Fri, 26 Aug 2022 19:36:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344469AbiHZTgR (ORCPT ); Fri, 26 Aug 2022 15:36:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42182 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230408AbiHZTgM (ORCPT ); Fri, 26 Aug 2022 15:36:12 -0400 Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA82DCE49A; Fri, 26 Aug 2022 12:36:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1661542571; x=1693078571; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=iSj/SuZhPON+rDmdOdwBzP5dOtaScuuVxlTIXwYMKPE=; b=DRt/p4S7CY0viVcYn0LywGrg+HrBcUCJhmQLo8HoqzUeYB+qRvxyVvW4 gWyjgvOcuAcIMJ/H1xXOgDwKthBmpEGvKcburnsLqDO6ysDPZ2UFszDkV w8EBCSGY0Bxh69TojQBDItbGWGzWO5GtEP/IIuRGesOdWli5ryVA94Mcj Yh5Df2M0RNiq6ZbL+DJe+ACClc+OMagH9q8VdfUUBzaNPYlBdUv5q2Txm W74U0MebEUWCxTQZZnZkzyzPCwtn700sJwwjcxqFZ06ybZhAYY17fktmn lXNr6sk/J9Fb0rKeMLP3vkCjjk89bpgYqqxtEzA1xqCRjFxi7zPbx2SRC g==; X-IronPort-AV: E=McAfee;i="6500,9779,10451"; a="274332374" X-IronPort-AV: E=Sophos;i="5.93,266,1654585200"; d="scan'208";a="274332374" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Aug 2022 12:36:11 -0700 X-IronPort-AV: E=Sophos;i="5.93,266,1654585200"; d="scan'208";a="671592528" Received: from ahunter6-mobl1.ger.corp.intel.com (HELO [10.0.2.15]) ([10.252.50.209]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Aug 2022 12:36:00 -0700 Message-ID: <5a0b4083-084a-56b3-a6a1-0fad1100a316@intel.com> Date: Fri, 26 Aug 2022 22:35:53 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.11.0 Subject: Re: [PATCH v3 16/18] perf sched: Fixes for thread safety analysis Content-Language: en-US To: Namhyung Kim , Ian Rogers Cc: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Thomas Gleixner , Darren Hart , Davidlohr Bueso , =?UTF-8?Q?Andr=c3=a9_Almeida?= , Nathan Chancellor , Nick Desaulniers , Tom Rix , Weiguo Li , Athira Rajeev , Thomas Richter , Ravi Bangoria , Dario Petrillo , Hewenliang , yaowenbin , Wenyu Liu , Song Liu , Andrii Nakryiko , Dave Marchevsky , Leo Yan , Kim Phillips , Pavithra Gurushankar , Alexandre Truong , Quentin Monnet , William Cohen , Andres Freund , =?UTF-8?Q?Martin_Li=c5=a1ka?= , Colin Ian King , James Clark , Fangrui Song , Stephane Eranian , Kajol Jain , Alexey Bayduraev , Riccardo Mancini , Andi Kleen , Masami Hiramatsu , Zechuan Chen , Jason Wang , Christophe JAILLET , Remi Bernon , linux-kernel , linux-perf-users , bpf , llvm@lists.linux.dev References: <20220824153901.488576-1-irogers@google.com> <20220824153901.488576-17-irogers@google.com> From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/08/22 21:26, Namhyung Kim wrote: > On Fri, Aug 26, 2022 at 10:48 AM Ian Rogers wrote: >> >> On Fri, Aug 26, 2022 at 10:41 AM Adrian Hunter wrote: >>> >>> On 26/08/22 19:06, Ian Rogers wrote: >>>> On Fri, Aug 26, 2022 at 5:12 AM Adrian Hunter wrote: >>>>> >>>>> On 24/08/22 18:38, Ian Rogers wrote: >>>>>> Add annotations to describe lock behavior. Add unlocks so that mutexes >>>>>> aren't conditionally held on exit from perf_sched__replay. Add an exit >>>>>> variable so that thread_func can terminate, rather than leaving the >>>>>> threads blocked on mutexes. >>>>>> >>>>>> Signed-off-by: Ian Rogers >>>>>> --- >>>>>> tools/perf/builtin-sched.c | 46 ++++++++++++++++++++++++-------------- >>>>>> 1 file changed, 29 insertions(+), 17 deletions(-) >>>>>> >>>>>> diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c >>>>>> index 7e4006d6b8bc..b483ff0d432e 100644 >>>>>> --- a/tools/perf/builtin-sched.c >>>>>> +++ b/tools/perf/builtin-sched.c >>>>>> @@ -246,6 +246,7 @@ struct perf_sched { >>>>>> const char *time_str; >>>>>> struct perf_time_interval ptime; >>>>>> struct perf_time_interval hist_time; >>>>>> + volatile bool thread_funcs_exit; >>>>>> }; >>>>>> >>>>>> /* per thread run time data */ >>>>>> @@ -633,31 +634,34 @@ static void *thread_func(void *ctx) >>>>>> prctl(PR_SET_NAME, comm2); >>>>>> if (fd < 0) >>>>>> return NULL; >>>>>> -again: >>>>>> - ret = sem_post(&this_task->ready_for_work); >>>>>> - BUG_ON(ret); >>>>>> - mutex_lock(&sched->start_work_mutex); >>>>>> - mutex_unlock(&sched->start_work_mutex); >>>>>> >>>>>> - cpu_usage_0 = get_cpu_usage_nsec_self(fd); >>>>>> + while (!sched->thread_funcs_exit) { >>>>>> + ret = sem_post(&this_task->ready_for_work); >>>>>> + BUG_ON(ret); >>>>>> + mutex_lock(&sched->start_work_mutex); >>>>>> + mutex_unlock(&sched->start_work_mutex); >>>>>> >>>>>> - for (i = 0; i < this_task->nr_events; i++) { >>>>>> - this_task->curr_event = i; >>>>>> - perf_sched__process_event(sched, this_task->atoms[i]); >>>>>> - } >>>>>> + cpu_usage_0 = get_cpu_usage_nsec_self(fd); >>>>>> >>>>>> - cpu_usage_1 = get_cpu_usage_nsec_self(fd); >>>>>> - this_task->cpu_usage = cpu_usage_1 - cpu_usage_0; >>>>>> - ret = sem_post(&this_task->work_done_sem); >>>>>> - BUG_ON(ret); >>>>>> + for (i = 0; i < this_task->nr_events; i++) { >>>>>> + this_task->curr_event = i; >>>>>> + perf_sched__process_event(sched, this_task->atoms[i]); >>>>>> + } >>>>>> >>>>>> - mutex_lock(&sched->work_done_wait_mutex); >>>>>> - mutex_unlock(&sched->work_done_wait_mutex); >>>>>> + cpu_usage_1 = get_cpu_usage_nsec_self(fd); >>>>>> + this_task->cpu_usage = cpu_usage_1 - cpu_usage_0; >>>>>> + ret = sem_post(&this_task->work_done_sem); >>>>>> + BUG_ON(ret); >>>>>> >>>>>> - goto again; >>>>>> + mutex_lock(&sched->work_done_wait_mutex); >>>>>> + mutex_unlock(&sched->work_done_wait_mutex); >>>>>> + } >>>>>> + return NULL; >>>>>> } >>>>>> >>>>>> static void create_tasks(struct perf_sched *sched) >>>>>> + EXCLUSIVE_LOCK_FUNCTION(sched->start_work_mutex) >>>>>> + EXCLUSIVE_LOCK_FUNCTION(sched->work_done_wait_mutex) >>>>>> { >>>>>> struct task_desc *task; >>>>>> pthread_attr_t attr; >>>>>> @@ -687,6 +691,8 @@ static void create_tasks(struct perf_sched *sched) >>>>>> } >>>>>> >>>>>> static void wait_for_tasks(struct perf_sched *sched) >>>>>> + EXCLUSIVE_LOCKS_REQUIRED(sched->work_done_wait_mutex) >>>>>> + EXCLUSIVE_LOCKS_REQUIRED(sched->start_work_mutex) >>>>>> { >>>>>> u64 cpu_usage_0, cpu_usage_1; >>>>>> struct task_desc *task; >>>>>> @@ -738,6 +744,8 @@ static void wait_for_tasks(struct perf_sched *sched) >>>>>> } >>>>>> >>>>>> static void run_one_test(struct perf_sched *sched) >>>>>> + EXCLUSIVE_LOCKS_REQUIRED(sched->work_done_wait_mutex) >>>>>> + EXCLUSIVE_LOCKS_REQUIRED(sched->start_work_mutex) >>>>>> { >>>>>> u64 T0, T1, delta, avg_delta, fluct; >>>>>> >>>>>> @@ -3309,11 +3317,15 @@ static int perf_sched__replay(struct perf_sched *sched) >>>>>> print_task_traces(sched); >>>>>> add_cross_task_wakeups(sched); >>>>>> >>>>>> + sched->thread_funcs_exit = false; >>>>>> create_tasks(sched); >>>>>> printf("------------------------------------------------------------\n"); >>>>>> for (i = 0; i < sched->replay_repeat; i++) >>>>>> run_one_test(sched); >>>>>> >>>>>> + sched->thread_funcs_exit = true; >>>>>> + mutex_unlock(&sched->start_work_mutex); >>>>>> + mutex_unlock(&sched->work_done_wait_mutex); >>>>> >>>>> I think you still need to wait for the threads to exit before >>>>> destroying the mutexes. >>>> >>>> This is a pre-existing issue and beyond the scope of this patch set. >>> >>> You added the mutex_destroy functions in patch 8, so it is still >>> fallout from that. >> >> In the previous code the threads were blocked on mutexes that were >> stack allocated and the stack memory went away. You are correct to say >> that to those locks I added an init and destroy call. The lifetime of >> the mutex was wrong previously and remains wrong in this change. > > I think you fixed the lifetime issue with sched->thread_funcs_exit here. > All you need to do is calling pthread_join() after the mutex_unlock, no? Like this maybe: diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c index b483ff0d432e..8090c1218855 100644 --- a/tools/perf/builtin-sched.c +++ b/tools/perf/builtin-sched.c @@ -3326,6 +3326,13 @@ static int perf_sched__replay(struct perf_sched *sched) sched->thread_funcs_exit = true; mutex_unlock(&sched->start_work_mutex); mutex_unlock(&sched->work_done_wait_mutex); + /* Get rid of threads so they won't be upset by mutex destruction */ + for (i = 0; i < sched->nr_tasks; i++) { + int err = pthread_join(sched->tasks[i]->thread, NULL); + + if (err) + pr_err("pthread_join() failed for task nr %lu, error %d\n", i, err); + } return 0; }