From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754693Ab0JRJoT (ORCPT ); Mon, 18 Oct 2010 05:44:19 -0400 Received: from gir.skynet.ie ([193.1.99.77]:53573 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753234Ab0JRJoR (ORCPT ); Mon, 18 Oct 2010 05:44:17 -0400 Date: Mon, 18 Oct 2010 10:44:04 +0100 From: Mel Gorman To: Tejun Heo Cc: lkml , KAMEZAWA Hiroyuki , Andrew Morton , Wu Fengguang , Michal Hocko Subject: Re: [PATCH v2.6.36-rc7] memory_hotplug: drop spurious calls to flush_scheduled_work() Message-ID: <20101018094403.GW30667@csn.ul.ie> References: <4CB8725B.9010200@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <4CB8725B.9010200@kernel.org> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 15, 2010 at 05:25:15PM +0200, Tejun Heo wrote: > lru_add_drain_all() uses schedule_on_each_cpu() which is synchronous. > There is no reason to call flush_scheduled_work() after > lru_add_drain_all(). Drop the spurious calls. > This looks correct. Acked-by: Mel Gorman I suspect this call to flush_scheduled_work() existed because it is easy to interpret the documentation of schedule_on_each_cpu to mean it is an asynchronous call. Maybe something like the following? ==== CUT HERE ==== workqueue: Clarify that schedule_on_each_cpu is synchronous The documentation for schedule_on_each_cpu() states that it calls a function on each online CPU from keventd. This can easily be interpreted as an asyncronous call because the description does not mention that flush_work is called. Clarify that it is synchronous. Signed-off-by: Mel Gorman --- kernel/workqueue.c | 8 +++++--- 1 files changed, 5 insertions(+), 3 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index f77afd9..07cba1e 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2592,13 +2592,15 @@ int schedule_delayed_work_on(int cpu, EXPORT_SYMBOL(schedule_delayed_work_on); /** - * schedule_on_each_cpu - call a function on each online CPU from keventd + * schedule_on_each_cpu - Call a function on each online CPU via keventd and wait for completion * @func: the function to call * + * schedule_on_each_cpu executes a given callback function on each CPU via keventd + * and blocks until each callback has completed. schedule_on_each_cpu() is very + * slow. + * * Returns zero on success. * Returns -ve errno on failure. - * - * schedule_on_each_cpu() is very slow. */ int schedule_on_each_cpu(work_func_t func) {