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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 3B4AEC433DF for ; Mon, 12 Oct 2020 16:16:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DC35020797 for ; Mon, 12 Oct 2020 16:16:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="hmJR1R1d" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403766AbgJLQQU (ORCPT ); Mon, 12 Oct 2020 12:16:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390043AbgJLQQU (ORCPT ); Mon, 12 Oct 2020 12:16:20 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2697CC0613D0 for ; Mon, 12 Oct 2020 09:16:20 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id c196so6885332ybf.0 for ; Mon, 12 Oct 2020 09:16:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:message-id:mime-version:subject:from:to:cc; bh=graV3pGKh1wSZY3RtXTrko5CERBJDFLNGxisxbtlJMw=; b=hmJR1R1dur4ua18it34enqX+n5x5y0EvwVfbAsgm7qP5x7BTZjWf5sof12NZA2T5RD hl+KP6bE7+CmAlsYlsaooToVv2MgT+Yg/hiqGkwd+CZEnqYF+FNw39yo8Q2OJSXnMtQH DdRW3eqRNy+SY3BTeZnrBznxMYMI1w8UNE/Xrig049cP/BzVV1XzK2LMlO5YJl4YBFZg Zq3bV+1UQ+3yZ+pBrMn0godTadJh5178YuNSE/omP0Ixg7XwNc3AjfyUeUH1tigKmxyu toWL9HRsbd7UJH0t+Y0XAvFuoFWgWEoFeZO2UZ825AOOgPOVcJ4isHhC3XDDXySppTm5 yQMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:message-id:mime-version:subject:from :to:cc; bh=graV3pGKh1wSZY3RtXTrko5CERBJDFLNGxisxbtlJMw=; b=hSGVuCsS9rwx5H0FdePAi2Ed6VT/8Su/IAhtSCKuGKQX95SRfoXfTgi25gvwbybF4+ lKdgdPaAz4Fal32QI9UsBsT78hQp3Rpcv0B/zqKyI9XV5PoZLxUpi9DiFoEbUbBnqKQc BalTCWLe4UYjJiH8FkfciLg9Oo8jPWqufa0K1bpCrXkfVdSMTVUPCZLrSJjpJSYpRpzD FLdMD184G33jDArlyJD/LU0qLHc0JrFj9+OvOYUV22amquoItcOycqSs9Lp2KqVEoIPO LAnXww6qgUnphbWxmCSgsINIO/Ut9iDfo4v+40uAAo6n4sTt5xJD/t3fvfz10LoWkoqh 8Ptg== X-Gm-Message-State: AOAM532PjeZey0Lde9fU9W3XtquH1Iq7sS2DuiOQGR0+SUlQJwH74d9C NodyUelmyqkK4mr9Rz0hgHhlJXlatloX X-Google-Smtp-Source: ABdhPJzEx7g8DCF4p6ZkuOEX6HEuWobfi3/dLtAPZ6S90xvqI15QiEGD9YiX1NqaGpXJRe3xSgw0GB+se8Pr Sender: "irogers via sendgmr" X-Received: from irogers.svl.corp.google.com ([2620:15c:2cd:2:f693:9fff:fef4:4583]) (user=irogers job=sendgmr) by 2002:a25:e649:: with SMTP id d70mr13241751ybh.127.1602519379310; Mon, 12 Oct 2020 09:16:19 -0700 (PDT) Date: Mon, 12 Oct 2020 09:16:11 -0700 Message-Id: <20201012161611.366482-1-irogers@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.1011.ga647a8990f-goog Subject: [PATCH v2] perf bench: Use condition variables in numa. From: Ian Rogers To: Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Alexander Gordeev , Srikar Dronamraju , Peng Fan , linux-kernel@vger.kernel.org Cc: Stephane Eranian , Ian Rogers Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The existing approach to synchronization between threads in the numa benchmark is unbalanced mutexes. This synchronization causes thread sanitizer to warn of locks being taken twice on a thread without an unlock, as well as unlocks with no corresponding locks. This change replaces the synchronization with more regular condition variables. While this fixes one class of thread sanitizer warnings, there still remain warnings of data races due to threads reading and writing shared memory without any atomics. Signed-off-by: Ian Rogers --- tools/perf/bench/numa.c | 67 ++++++++++++++++++++++++++++------------- 1 file changed, 46 insertions(+), 21 deletions(-) diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c index f85bceccc459..11726ec6285f 100644 --- a/tools/perf/bench/numa.c +++ b/tools/perf/bench/numa.c @@ -137,12 +137,13 @@ struct global_info { u8 *data; pthread_mutex_t startup_mutex; + pthread_cond_t startup_cond; int nr_tasks_started; - pthread_mutex_t startup_done_mutex; - pthread_mutex_t start_work_mutex; + pthread_cond_t start_work_cond; int nr_tasks_working; + bool start_work; pthread_mutex_t stop_work_mutex; u64 bytes_done; @@ -483,6 +484,18 @@ static void init_global_mutex(pthread_mutex_t *mutex) pthread_mutex_init(mutex, &attr); } +/* + * Return a process-shared (global) condition variable: + */ +static void init_global_cond(pthread_cond_t *cond) +{ + pthread_condattr_t attr; + + pthread_condattr_init(&attr); + pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); + pthread_cond_init(cond, &attr); +} + static int parse_cpu_list(const char *arg) { p0.cpu_list_str = strdup(arg); @@ -1136,15 +1149,18 @@ static void *worker_thread(void *__tdata) if (g->p.serialize_startup) { pthread_mutex_lock(&g->startup_mutex); g->nr_tasks_started++; + /* The last thread wakes the main process. */ + if (g->nr_tasks_started == g->p.nr_tasks) + pthread_cond_signal(&g->startup_cond); + pthread_mutex_unlock(&g->startup_mutex); /* Here we will wait for the main process to start us all at once: */ pthread_mutex_lock(&g->start_work_mutex); + g->start_work = false; g->nr_tasks_working++; - - /* Last one wake the main process: */ - if (g->nr_tasks_working == g->p.nr_tasks) - pthread_mutex_unlock(&g->startup_done_mutex); + while (!g->start_work) + pthread_cond_wait(&g->start_work_cond, &g->start_work_mutex); pthread_mutex_unlock(&g->start_work_mutex); } @@ -1441,8 +1457,9 @@ static int init(void) /* Startup serialization: */ init_global_mutex(&g->start_work_mutex); + init_global_cond(&g->start_work_cond); init_global_mutex(&g->startup_mutex); - init_global_mutex(&g->startup_done_mutex); + init_global_cond(&g->startup_cond); init_global_mutex(&g->stop_work_mutex); init_thread_data(); @@ -1502,9 +1519,6 @@ static int __bench_numa(const char *name) pids = zalloc(g->p.nr_proc * sizeof(*pids)); pid = -1; - /* All threads try to acquire it, this way we can wait for them to start up: */ - pthread_mutex_lock(&g->start_work_mutex); - if (g->p.serialize_startup) { tprintf(" #\n"); tprintf(" # Startup synchronization: ..."); fflush(stdout); @@ -1526,22 +1540,29 @@ static int __bench_numa(const char *name) pids[i] = pid; } - /* Wait for all the threads to start up: */ - while (g->nr_tasks_started != g->p.nr_tasks) - usleep(USEC_PER_MSEC); - - BUG_ON(g->nr_tasks_started != g->p.nr_tasks); if (g->p.serialize_startup) { + bool threads_ready = false; double startup_sec; - pthread_mutex_lock(&g->startup_done_mutex); + /* + * Wait for all the threads to start up. The last thread will + * signal this process. + */ + pthread_mutex_lock(&g->startup_mutex); + while (g->nr_tasks_started != g->p.nr_tasks) + pthread_cond_wait(&g->startup_cond, &g->startup_mutex); - /* This will start all threads: */ - pthread_mutex_unlock(&g->start_work_mutex); + pthread_mutex_unlock(&g->startup_mutex); - /* This mutex is locked - the last started thread will wake us: */ - pthread_mutex_lock(&g->startup_done_mutex); + /* Wait for all threads to be at the start_work_cond. */ + while (!threads_ready) { + pthread_mutex_lock(&g->start_work_mutex); + threads_ready = (g->nr_tasks_working == g->p.nr_tasks); + pthread_mutex_unlock(&g->start_work_mutex); + if (!threads_ready) + usleep(1); + } gettimeofday(&stop, NULL); @@ -1555,7 +1576,11 @@ static int __bench_numa(const char *name) tprintf(" #\n"); start = stop; - pthread_mutex_unlock(&g->startup_done_mutex); + /* Start all threads running. */ + pthread_mutex_lock(&g->start_work_mutex); + g->start_work = true; + pthread_mutex_unlock(&g->start_work_mutex); + pthread_cond_broadcast(&g->start_work_cond); } else { gettimeofday(&start, NULL); } -- 2.28.0.1011.ga647a8990f-goog