Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:45182 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754869AbZJGTQp (ORCPT ); Wed, 7 Oct 2009 15:16:45 -0400 Date: Wed, 7 Oct 2009 15:01:06 -0400 From: "John W. Linville" To: Larry Finger Cc: linux-wireless@vger.kernel.org Subject: Re: [PATCH] b43: Fix locking problem when stopping rfkill polling Message-ID: <20091007190106.GB22394@tuxdriver.com> References: <4accae5d.BgSJpcmlvg+W5PGM%Larry.Finger@lwfinger.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <4accae5d.BgSJpcmlvg+W5PGM%Larry.Finger@lwfinger.net> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, Oct 07, 2009 at 10:06:05AM -0500, Larry Finger wrote: > In commit 26e5ab35b4c7b1d4cb487a11084520aed9a8d05e entitled "b43: Fix PPC > crash in rfkill polling on unload", the call to stop polling should not have > been placed inside the wl->mutex. The result was incorrect locking messages. > > Signed-off-by: Larry Finger > --- > > John, > > I had not intended for the previous patch to be applied as I was waiting for > the Bugzilla OP to test. He promised to do that today. In any case, that patch > introduced a locking problem that needs to be fixed. > > Why do the one-liners cause so many problems? > > Larry > --- > > Index: wireless-testing/drivers/net/wireless/b43/main.c > =================================================================== > --- wireless-testing.orig/drivers/net/wireless/b43/main.c > +++ wireless-testing/drivers/net/wireless/b43/main.c > @@ -4501,8 +4501,8 @@ static void b43_op_stop(struct ieee80211 > > cancel_work_sync(&(wl->beacon_update_trigger)); > > - mutex_lock(&wl->mutex); > wiphy_rfkill_stop_polling(hw->wiphy); > + mutex_lock(&wl->mutex); > if (b43_status(dev) >= B43_STAT_STARTED) { > dev = b43_wireless_core_stop(dev); > if (!dev) OK, but why do we start polling under the lock but stop polling without the lock? Should we start polling without holding the lock too? John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.