From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752272AbaJSTlt (ORCPT ); Sun, 19 Oct 2014 15:41:49 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:46689 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751980AbaJSTls (ORCPT ); Sun, 19 Oct 2014 15:41:48 -0400 Date: Sun, 19 Oct 2014 20:40:55 +0100 From: Mark Rutland To: Mark Salter Cc: Daniel Lezcano , Sudeep Holla , Thomas Gleixner , Stephen Boyd , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] clocksource: arm_arch_timer: fix system hang Message-ID: <20141019194055.GA24830@leverpostej> References: <1413732164-19545-1-git-send-email-msalter@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1413732164-19545-1-git-send-email-msalter@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, On Sun, Oct 19, 2014 at 04:22:44PM +0100, Mark Salter wrote: > Arm allows for two possible architectural clock sources. One memory mapped > and the other coprocessor based. If both timers exist, then the driver waits > for both to be probed before registering a clocksource. > > Commit c387f07e6205 ("clocksource: arm_arch_timer: Discard unavailable timers > correctly") attempted to fix a hang occurring when one of the two possible > timers had a device node, but was disabled. In that case, the second probe > would never occur and the system would hang without a clocksource being > registered. > > Unfortunately, incorrect logic in that commit made things worse such that > a hang would occur unless both timers had a device node and were enabled. > This patch fixes the logic so that we don't wait to probe a second timer > unless it exists and is enabled. > > Signed-off-by: Mark Salter Marc Zyngier had a similar fix for this issue a few days ago [1]. > --- > drivers/clocksource/arm_arch_timer.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index d1a5e35..b73392b 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -666,13 +666,14 @@ static bool __init > arch_timer_probed(int type, const struct of_device_id *matches) > { > struct device_node *dn; > - bool probed = false; > + bool probed = true; > > dn = of_find_matching_node(NULL, matches); > - if (dn && of_device_is_available(dn) && (arch_timers_present & type)) > - probed = true; > - of_node_put(dn); > - > + if (dn) { > + if (of_device_is_available(dn) && !(arch_timers_present & type)) > + probed = false; > + of_node_put(dn); > + } Other than the addition of the NULL check, this looks identical to Marc's fix. There's already a NULL check in of_device_is_available, so I don't think it's necessary to add one here. Are you seeing some failure with a NULL np? Thanks, Mark. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2014-October/294744.html