From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760196AbaGZDE1 (ORCPT ); Fri, 25 Jul 2014 23:04:27 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:16072 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751853AbaGZDEF (ORCPT ); Fri, 25 Jul 2014 23:04:05 -0400 X-IronPort-AV: E=Sophos;i="5.00,965,1396972800"; d="scan'208";a="33802426" From: Lai Jiangshan To: CC: Tejun Heo , Lai Jiangshan Subject: [PATCH 1/3] workqueue: migrate the new worker before add it to idle_list Date: Sat, 26 Jul 2014 11:04:49 +0800 Message-ID: <1406343900-32423-2-git-send-email-laijs@cn.fujitsu.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1406343900-32423-1-git-send-email-laijs@cn.fujitsu.com> References: <1406343900-32423-1-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.167.226.103] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is an undocumented requirement for create_worker() that it can only be called from existing worker (aka. manager) except the first call. The reason is that the current create_worker() queues the new worker to idle_list at first and then wake up it. But the new worker is not guaranteed to be migrated until it is waken up. Thus the wq_worker_sleeping() may see the new non-local worker from the idle_list if this block of code is not executed on the local CPU to disable wq_worker_sleeping(). Existing worker can guarantee to run on local CPU when !DISASSOCIATED, so create_worker() is required to be called from existing worker/manager only currently. But we are planning to allow create_worker() to be called out side from its workers and the requirement should be alleviated. So we exchange the order of the code, the new worker is woken up before queued to idle_list. Signed-off-by: Lai Jiangshan --- kernel/workqueue.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 370f947..1d44d8d 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1708,8 +1708,13 @@ static struct worker *create_worker(struct worker_pool *pool) /* start the newly created worker */ spin_lock_irq(&pool->lock); worker->pool->nr_workers++; - worker_enter_idle(worker); + /* + * Wake up the worker at first and then queue it to the idle_list, + * so that it is ensued that the wq_worker_sleeping() sees the worker + * had been migrated properly when sees this worker in the idle_list. + */ wake_up_process(worker->task); + worker_enter_idle(worker); spin_unlock_irq(&pool->lock); return worker; -- 1.7.4.4