From patchwork Mon Feb 21 09:56:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Denis V. Lunev\" via" X-Patchwork-Id: 12753363 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 27FF0C433EF for ; Mon, 21 Feb 2022 10:11:47 +0000 (UTC) Received: from localhost ([::1]:56560 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nM5fW-0007z5-0C for qemu-devel@archiver.kernel.org; Mon, 21 Feb 2022 05:11:46 -0500 Received: from eggs.gnu.org ([209.51.188.92]:49596) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nM5Qu-0008GC-9C for qemu-devel@nongnu.org; Mon, 21 Feb 2022 04:56:40 -0500 Received: from szxga02-in.huawei.com ([45.249.212.188]:5103) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nM5Qs-0005PO-2Q for qemu-devel@nongnu.org; Mon, 21 Feb 2022 04:56:39 -0500 Received: from dggpeml500020.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4K2Hhh2Cj9z9ss1; Mon, 21 Feb 2022 17:54:44 +0800 (CST) Received: from dggpeml100016.china.huawei.com (7.185.36.216) by dggpeml500020.china.huawei.com (7.185.36.88) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 21 Feb 2022 17:56:24 +0800 Received: from DESKTOP-27KDQMV.china.huawei.com (10.174.148.223) by dggpeml100016.china.huawei.com (7.185.36.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 21 Feb 2022 17:56:24 +0800 To: , , CC: , , "Longpeng(Mike)" Subject: [RFC 1/2] sem-posix: remove the posix semaphore support Date: Mon, 21 Feb 2022 17:56:16 +0800 Message-ID: <20220221095617.1974-2-longpeng2@huawei.com> X-Mailer: git-send-email 2.25.0.windows.1 In-Reply-To: <20220221095617.1974-1-longpeng2@huawei.com> References: <20220221095617.1974-1-longpeng2@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.148.223] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml100016.china.huawei.com (7.185.36.216) X-CFilter-Loop: Reflected Received-SPF: pass client-ip=45.249.212.188; envelope-from=longpeng2@huawei.com; helo=szxga02-in.huawei.com X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Reply-to: "Longpeng(Mike)" X-Patchwork-Original-From: "Longpeng(Mike)" via From: "Denis V. Lunev\" via" POSIX specifies an absolute time for sem_timedwait(), it would be affected if the system time is changing, but there is not a relative time or monotonic clock version of sem_timedwait, so we cannot gain from POSIX semaphore anymore. An alternative way is to use sem_trywait + usleep, maybe we can remove CONFIG_SEM_TIMEDWAIT in this way? No, because some systems (e.g. mac os) mark the sem_xxx API as deprecated. So maybe remove the usage of POSIX semaphore and turn to use the pthread variant for all systems looks better. Signed-off-by: Longpeng(Mike) --- include/qemu/thread-posix.h | 4 ---- meson.build | 1 - util/qemu-thread-posix.c | 54 --------------------------------------------- 3 files changed, 59 deletions(-) diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h index b792e6e..5466608 100644 --- a/include/qemu/thread-posix.h +++ b/include/qemu/thread-posix.h @@ -27,13 +27,9 @@ struct QemuCond { }; struct QemuSemaphore { -#ifndef CONFIG_SEM_TIMEDWAIT pthread_mutex_t lock; pthread_cond_t cond; unsigned int count; -#else - sem_t sem; -#endif bool initialized; }; diff --git a/meson.build b/meson.build index 762d7ce..3ccb110 100644 --- a/meson.build +++ b/meson.build @@ -1557,7 +1557,6 @@ config_host_data.set('CONFIG_POSIX_FALLOCATE', cc.has_function('posix_fallocate' config_host_data.set('CONFIG_POSIX_MEMALIGN', cc.has_function('posix_memalign')) config_host_data.set('CONFIG_PPOLL', cc.has_function('ppoll')) config_host_data.set('CONFIG_PREADV', cc.has_function('preadv', prefix: '#include ')) -config_host_data.set('CONFIG_SEM_TIMEDWAIT', cc.has_function('sem_timedwait', dependencies: threads)) config_host_data.set('CONFIG_SENDFILE', cc.has_function('sendfile')) config_host_data.set('CONFIG_SETNS', cc.has_function('setns') and cc.has_function('unshare')) config_host_data.set('CONFIG_SYNCFS', cc.has_function('syncfs')) diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c index e1225b6..1ad2503 100644 --- a/util/qemu-thread-posix.c +++ b/util/qemu-thread-posix.c @@ -219,7 +219,6 @@ void qemu_sem_init(QemuSemaphore *sem, int init) { int rc; -#ifndef CONFIG_SEM_TIMEDWAIT rc = pthread_mutex_init(&sem->lock, NULL); if (rc != 0) { error_exit(rc, __func__); @@ -232,12 +231,6 @@ void qemu_sem_init(QemuSemaphore *sem, int init) error_exit(EINVAL, __func__); } sem->count = init; -#else - rc = sem_init(&sem->sem, 0, init); - if (rc < 0) { - error_exit(errno, __func__); - } -#endif sem->initialized = true; } @@ -247,7 +240,6 @@ void qemu_sem_destroy(QemuSemaphore *sem) assert(sem->initialized); sem->initialized = false; -#ifndef CONFIG_SEM_TIMEDWAIT rc = pthread_cond_destroy(&sem->cond); if (rc < 0) { error_exit(rc, __func__); @@ -256,12 +248,6 @@ void qemu_sem_destroy(QemuSemaphore *sem) if (rc < 0) { error_exit(rc, __func__); } -#else - rc = sem_destroy(&sem->sem); - if (rc < 0) { - error_exit(errno, __func__); - } -#endif } void qemu_sem_post(QemuSemaphore *sem) @@ -269,7 +255,6 @@ void qemu_sem_post(QemuSemaphore *sem) int rc; assert(sem->initialized); -#ifndef CONFIG_SEM_TIMEDWAIT pthread_mutex_lock(&sem->lock); if (sem->count == UINT_MAX) { rc = EINVAL; @@ -281,12 +266,6 @@ void qemu_sem_post(QemuSemaphore *sem) if (rc != 0) { error_exit(rc, __func__); } -#else - rc = sem_post(&sem->sem); - if (rc < 0) { - error_exit(errno, __func__); - } -#endif } int qemu_sem_timedwait(QemuSemaphore *sem, int ms) @@ -295,7 +274,6 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms) struct timespec ts; assert(sem->initialized); -#ifndef CONFIG_SEM_TIMEDWAIT rc = 0; compute_abs_deadline(&ts, ms); pthread_mutex_lock(&sem->lock); @@ -313,29 +291,6 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms) } pthread_mutex_unlock(&sem->lock); return (rc == ETIMEDOUT ? -1 : 0); -#else - if (ms <= 0) { - /* This is cheaper than sem_timedwait. */ - do { - rc = sem_trywait(&sem->sem); - } while (rc == -1 && errno == EINTR); - if (rc == -1 && errno == EAGAIN) { - return -1; - } - } else { - compute_abs_deadline(&ts, ms); - do { - rc = sem_timedwait(&sem->sem, &ts); - } while (rc == -1 && errno == EINTR); - if (rc == -1 && errno == ETIMEDOUT) { - return -1; - } - } - if (rc < 0) { - error_exit(errno, __func__); - } - return 0; -#endif } void qemu_sem_wait(QemuSemaphore *sem) @@ -343,7 +298,6 @@ void qemu_sem_wait(QemuSemaphore *sem) int rc; assert(sem->initialized); -#ifndef CONFIG_SEM_TIMEDWAIT pthread_mutex_lock(&sem->lock); while (sem->count == 0) { rc = pthread_cond_wait(&sem->cond, &sem->lock); @@ -353,14 +307,6 @@ void qemu_sem_wait(QemuSemaphore *sem) } --sem->count; pthread_mutex_unlock(&sem->lock); -#else - do { - rc = sem_wait(&sem->sem); - } while (rc == -1 && errno == EINTR); - if (rc < 0) { - error_exit(errno, __func__); - } -#endif } #ifdef __linux__