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=-8.9 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 7098EC04EB8 for ; Mon, 10 Dec 2018 21:20:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2214E2084E for ; Mon, 10 Dec 2018 21:20:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2214E2084E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arndb.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728191AbeLJVUV (ORCPT ); Mon, 10 Dec 2018 16:20:21 -0500 Received: from mout.kundenserver.de ([212.227.17.10]:42657 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726324AbeLJVUV (ORCPT ); Mon, 10 Dec 2018 16:20:21 -0500 Received: from wuerfel.lan ([109.192.41.194]) by mrelayeu.kundenserver.de (mreue107 [212.227.15.145]) with ESMTPA (Nemesis) id 1MmU1H-1hEdUW2RU1-00iULu; Mon, 10 Dec 2018 22:20:01 +0100 From: Arnd Bergmann To: Thomas Graf , Herbert Xu Cc: Arnd Bergmann , "David S. Miller" , NeilBrown , Tom Herbert , Kees Cook , Paul Blakey , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] test_rhashtable: remove semaphore usage Date: Mon, 10 Dec 2018 22:17:20 +0100 Message-Id: <20181210211957.210189-1-arnd@arndb.de> X-Mailer: git-send-email 2.20.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:ALCGaFg58WW3NSexPPpdxDr/NdIoNswdvn4CB7H4luNuXNDt0Sv VfX64FYnokCrVab+K8AT9C6ubv6/NZjomRTjWzZ7jwZl4YcUUesJ0DPUekui1OLOCwKvCco WXUYjZiS92yOvXhLGp7G0cVYHH2IXU5RfGIs/kqBYibZ3jmWQco7aSYb6ttcCwwRY7jU3zU hJMHNsBVPDezhgdQZ5T9A== X-UI-Out-Filterresults: notjunk:1;V03:K0:0Hmo5bsPMg4=:NABrAQ+hJlwADHEEFE9SEe VyVGxBvbw1zyk1UjNs92Amjr5hMiVBFTD2obpR70bzqT8PtmDFvBXs5FfOAwZ97ict8m+wQtV +S+jLwUhQKToy2Jq3sn5eJ2KXrSdeAsXJtB9y33RExIsXpUyShtUZY8F+Knx4Dz58S4uOvhrj 7LDbzT4wN/eAO5di7oIh7ha18CV8xYD7uxfRKLWdhGLt9KVfXVBrcSaby7FTscRRXTIiYnbJM 8vrOK11XqsSYa8n3Ts3QQDX45IBTYsLGTlzuZgJ8ylM28A7sm0swSXyA+Sp/eFNmhjLvByT1M j9SqZ48tiAIgmtNtGiEr64GBlbgDz8AWRmqrgsZtduQ+vxf1SypwXnzVCLoSKvRk5mZFznQo6 KVOO75AK6v8CEu6hAFK3YkZYVcCmKQclvOoSFkD3pUgIJsR3MWRyVT4uTew6QU8Cqaf95D5CJ J94Dbqy14QKP9e/HkV8+OQd+6FrhW1ck5BEZZ4NbQCJUcMrAissXw7eCivD+kxODDsXkX6IFL LfeZBuHNgJ7pqsePV6zxYHasIHjiY/vF6Kn25kIkFWTbvYV1OwMRaFIauQNjoZXf3feG3XPqN wvHZhPSGYZmFlcqVSK9G8VpBMhA6ci0Y+m7nZlAtmOgsLhdFjECe847DPGw08dvKFrVDeIvxO MTNmB1NYbNgJFxq0mRWUR4iVLZqRDbfX9z7yHtkSuDDLzEu3enWjnaclhoIrpm7jHv99gEiQF Kty4mvWFCyN8Wq5RnfiRoKJkoOub/wzoYnl9+g== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is one of only two files that initialize a semaphore to a negative value. We don't really need the two semaphores here at all, but can do the same thing in more conventional and more effient way, by using a single waitqueue and an atomic thread counter. This gets us a little bit closer to eliminating classic semaphores from the kernel. It also fixes a corner case where we fail to continue after one of the threads fails to start up. An alternative would be to use a split kthread_create()+wake_up_process() and completely eliminate the separate synchronization. Signed-off-by: Arnd Bergmann --- This is part of a longer, untested, series to remove semaphores from the kernel, please review as such before applying. --- lib/test_rhashtable.c | 28 ++++++++++++++++------------ 1 file changed, 16 insertions(+), 12 deletions(-) diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c index 18de5ff1255b..12bdea4f6c20 100644 --- a/lib/test_rhashtable.c +++ b/lib/test_rhashtable.c @@ -20,11 +20,11 @@ #include #include #include -#include #include #include #include #include +#include #define MAX_ENTRIES 1000000 #define TEST_INSERT_FAIL INT_MAX @@ -112,7 +112,8 @@ static struct rhashtable_params test_rht_params_dup = { .automatic_shrinking = false, }; -static struct semaphore prestart_sem, startup_sem; +static atomic_t startup_count; +static DECLARE_WAIT_QUEUE_HEAD(startup_wait); static int insert_retry(struct rhashtable *ht, struct test_obj *obj, const struct rhashtable_params params) @@ -635,8 +636,9 @@ static int threadfunc(void *data) int i, step, err = 0, insert_retries = 0; struct thread_data *tdata = data; - up(&prestart_sem); - if (down_interruptible(&startup_sem)) + if (atomic_dec_and_test(&startup_count)) + wake_up(&startup_wait); + if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == -1)) pr_err(" thread[%d]: down_interruptible failed\n", tdata->id); for (i = 0; i < tdata->entries; i++) { @@ -756,8 +758,7 @@ static int __init test_rht_init(void) pr_info("Testing concurrent rhashtable access from %d threads\n", tcount); - sema_init(&prestart_sem, 1 - tcount); - sema_init(&startup_sem, 0); + atomic_set(&startup_count, tcount); tdata = vzalloc(array_size(tcount, sizeof(struct thread_data))); if (!tdata) return -ENOMEM; @@ -783,15 +784,18 @@ static int __init test_rht_init(void) tdata[i].objs = objs + i * entries; tdata[i].task = kthread_run(threadfunc, &tdata[i], "rhashtable_thrad[%d]", i); - if (IS_ERR(tdata[i].task)) + if (IS_ERR(tdata[i].task)) { pr_err(" kthread_run failed for thread %d\n", i); - else + atomic_dec(&startup_count); + } else { started_threads++; + } } - if (down_interruptible(&prestart_sem)) - pr_err(" down interruptible failed\n"); - for (i = 0; i < tcount; i++) - up(&startup_sem); + if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == 0)) + pr_err(" wait_event interruptible failed\n"); + /* count is 0 now, set it to -1 and wake up all threads together */ + atomic_dec(&startup_count); + wake_up_all(&startup_wait); for (i = 0; i < tcount; i++) { if (IS_ERR(tdata[i].task)) continue; -- 2.20.0