From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Torokhov Subject: Re: [PATCH] atkbd: cancel delayed work before freeing its structure Date: Tue, 11 Nov 2008 09:51:56 -0500 Message-ID: <20081111145155.GA24881@anvil.corenet.prv> References: <20081105153140.25132ca1@psychotron.englab.brq.redhat.com> <20081107154325.GD9368@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from yx-out-2324.google.com ([74.125.44.29]:32294 "EHLO yx-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755479AbYKKOwB (ORCPT ); Tue, 11 Nov 2008 09:52:01 -0500 Received: by yx-out-2324.google.com with SMTP id 8so1176476yxm.1 for ; Tue, 11 Nov 2008 06:52:00 -0800 (PST) Content-Disposition: inline In-Reply-To: <20081107154325.GD9368@redhat.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Oleg Nesterov Cc: Jiri Pirko , linux-kernel@vger.kernel.org, linux-input@vger.kernel.org On Fri, Nov 07, 2008 at 04:43:25PM +0100, Oleg Nesterov wrote: > On 11/05, Jiri Pirko wrote: > > > > diff --git a/drivers/input/keyboard/atkbd.c b/drivers/input/keyboard/atkbd.c > > index 22016ca..f3bbf49 100644 > > --- a/drivers/input/keyboard/atkbd.c > > +++ b/drivers/input/keyboard/atkbd.c > > @@ -824,7 +824,7 @@ static void atkbd_disconnect(struct serio *serio) > > atkbd_disable(atkbd); > > > > /* make sure we don't have a command in flight */ > > - flush_scheduled_work(); > > + cancel_delayed_work_sync(&atkbd->event_work); > > Ping. Dmitry, could you take a look? > Applied, thank you. > > While we are here, what is the reason for atkbd_schedule_event_work()->wmb() ? > It looks absolutely bogus. Is it for atkbd_event_work() ? In that case it > is not needed, it must see all previous STOREs because both queue_work() and > run_workqueue() take cwq->lock. And in any case, > test_and_set_bit(WORK_STRUCT_PENDING) implies mb(). I wanted to be sure that event_mask is set before we schedule event_work and I don't want to rely on details of queue_delayed_work implementation. If the fact that queue_delayed_work acts as a barrier would be listed part of its published spec I would gladly remove wmb() from atkbd. > If schedule_delayed_work() > fails we can race with the soon-to-be-executed atkbd_event_work(), in that > case that test_and_set_bit() + test_and_clear_bit(->event_mask) save us, > but wmb() can't help again. > > Another question is why do we need ->event_mutex? OK, it can serialize > multiple instances of atkbd_event_work() running on the different CPUs, > but in that case atkbd_reconnect() needs this lock too? It also calls > atkbd_set_repeat_rate/atkbd_set_leds. Probably, I will need to thiknk about it a bit more. -- Dmitry