From mboxrd@z Thu Jan 1 00:00:00 1970 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Subject: Re: [PATCH] net: dsa: mv88e6xxx: fix races between lock and irq freeing Date: Sun, 22 Jul 2018 21:00:35 +0200 Message-ID: <20180722190035.ehav25wwwtz3fxfm@pengutronix.de> References: <20180720095315.21055-1-u.kleine-koenig@pengutronix.de> <20180721.224409.437815752648454744.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Cc: andrew@lunn.ch, vivien.didelot@savoirfairelinux.com, f.fainelli@gmail.com, netdev@vger.kernel.org, kernel@pengutronix.de To: David Miller Return-path: Received: from metis.ext.pengutronix.de ([85.220.165.71]:47993 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730699AbeGVT6U (ORCPT ); Sun, 22 Jul 2018 15:58:20 -0400 Content-Disposition: inline In-Reply-To: <20180721.224409.437815752648454744.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: Hello, On Sat, Jul 21, 2018 at 10:44:09PM -0700, David Miller wrote: > From: Uwe Kleine-König > Date: Fri, 20 Jul 2018 11:53:15 +0200 > > > free_irq() waits until all handlers for this IRQ have completed. As the > > relevant handler (mv88e6xxx_g1_irq_thread_fn()) takes the chip's reg_lock > > it might never return if the thread calling free_irq() holds this lock. > > > > For the same reason kthread_cancel_delayed_work_sync() in the polling case > > must not hold this lock. > > > > Also first free the irq (or stop the worker respectively) such that > > mv88e6xxx_g1_irq_thread_work() isn't called any more before the irq > > mappings are dropped in mv88e6xxx_g1_irq_free_common() to prevent the > > worker thread to call handle_nested_irq(0) which results in a NULL-pointer > > exception. > > > > Signed-off-by: Uwe Kleine-König > > Looks good. > > Note than the IRQ domain unmapping will do a synchronize_irq() which > should cause the same deadlock as free_irq() will with the reg_lock > held. Do you think that there is still a problem? When free_irq() for the external visible irq returns the muxed irqs should be all gone, too, so this should not trigger, should it? > Note also that g2 IRQ freeing gets the ordering right, and doesn't need > a lock because it doesn't program any registers when tearing down it's > IRQ. Yes. > Applied and queued up for -stable, thanks. Fine, thanks Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ |