From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753179AbaGNIMj (ORCPT ); Mon, 14 Jul 2014 04:12:39 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:43077 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751025AbaGNIMT (ORCPT ); Mon, 14 Jul 2014 04:12:19 -0400 X-IronPort-AV: E=Sophos;i="5.00,887,1396972800"; d="scan'208";a="33229592" From: Lai Jiangshan To: CC: Tejun Heo , Lai Jiangshan Subject: [PATCH 1/1 V2] workqueue: remove the del_timer_sync()s in maybe_create_worker() Date: Mon, 14 Jul 2014 16:13:21 +0800 Message-ID: <1405325601-12437-2-git-send-email-laijs@cn.fujitsu.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1405325601-12437-1-git-send-email-laijs@cn.fujitsu.com> References: <1405265479-827-1-git-send-email-laijs@cn.fujitsu.com> <1405325601-12437-1-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 It is said in the document that the timer which is being deleted by del_timer_sync() should not be restarted: Synchronization rules: Callers must prevent restarting of the timer, otherwise this function is meaningless. Repeating timer may cause the del_timer_sync() spin longer, or even spin forever in very very very very extreme condition. It is not considered a bug for me, but it disobeys the document. To fix it, we need: 1) don't requeue the mayday timer unless the manager is working it is a preparation/cleanup step for the fix. Otherwise the timer will repeat forever if we only do the 2). 2) remove the del_timer_sync()s in maybe_create_worker() the timer is still repeating, we should not use del_timer_sync(), let the timer dismiss itself. Change from V1: V1 incorrectly stops the timer when !need_to_create_worker(), but no one can restart it when needed. In V2, we stops the timer only when manager is not working. Signed-off-by: Lai Jiangshan --- kernel/workqueue.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 338d418..9c86a64 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1864,10 +1864,11 @@ static void pool_mayday_timeout(unsigned long __pool) send_mayday(work); } + if (mutex_is_locked(&pool->manager_arb)) + mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); + spin_unlock(&pool->lock); spin_unlock_irq(&wq_mayday_lock); - - mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); } /** @@ -1909,7 +1910,6 @@ restart: worker = create_worker(pool); if (worker) { - del_timer_sync(&pool->mayday_timer); spin_lock_irq(&pool->lock); start_worker(worker); if (WARN_ON_ONCE(need_to_create_worker(pool))) @@ -1926,7 +1926,6 @@ restart: break; } - del_timer_sync(&pool->mayday_timer); spin_lock_irq(&pool->lock); if (need_to_create_worker(pool)) goto restart; -- 1.7.4.4