From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH] atkbd: cancel delayed work before freeing its structure Date: Fri, 7 Nov 2008 16:43:25 +0100 Message-ID: <20081107154325.GD9368@redhat.com> References: <20081105153140.25132ca1@psychotron.englab.brq.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx2.redhat.com ([66.187.237.31]:51433 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750787AbYKGOmh (ORCPT ); Fri, 7 Nov 2008 09:42:37 -0500 Content-Disposition: inline In-Reply-To: <20081105153140.25132ca1@psychotron.englab.brq.redhat.com> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: dmitry.torokhov@gmail.com, Jiri Pirko Cc: linux-kernel@vger.kernel.org, linux-input@vger.kernel.org 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? 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(). 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. I don't understand this code, don't take my words too seriously, just curious. Oleg.