From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932174AbbA2Xv0 (ORCPT ); Thu, 29 Jan 2015 18:51:26 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:52857 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754525AbbA2XvY (ORCPT ); Thu, 29 Jan 2015 18:51:24 -0500 From: "Rafael J. Wysocki" To: Viresh Kumar Cc: Doug Anderson , Heiko Stuebner , Dmitry Torokhov , Chris Zhong , "linux-arm-kernel@lists.infradead.org" , Sonny Rao , Dylan Reid , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List Subject: Re: [PATCH v2] cpufreq: suspend cpufreq governors on shutdown Date: Fri, 30 Jan 2015 01:14:12 +0100 Message-ID: <1548953.lJ1trAVWhn@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.16.0-rc5+; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1419401388-20171-1-git-send-email-dianders@chromium.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Monday, December 29, 2014 09:45:42 AM Viresh Kumar wrote: > On 24 December 2014 at 11:39, Doug Anderson wrote: > > We should stop cpufreq governors when we shut down the system. If we > > don't do this, we can end up with this deadlock: > > > > 1. cpufreq governor may be running on a CPU other than CPU0. > > 2. In machine_restart() we call smp_send_stop() which stops CPUs. > > If one of these CPUs was actively running a cpufreq governor > > then it may have the mutex / spinlock needed to access the main > > PMIC in the system (perhaps over I2C) > > 3. If a machine needs access to the main PMIC in order to shutdown > > then it will never get it since the mutex was lost when the other > > CPU stopped. > > 4. We'll hang (possibly eventually hitting the hard lockup detector). > > > > Let's avoid the problem by stopping the cpufreq governor at shutdown, > > which is a sensible thing to do anyway. > > > > Signed-off-by: Doug Anderson > > --- > > Changes in v2: > > - Add a comment about why we register > > - Don't create cpufreq_shutdown() wrapper function > > > > drivers/cpufreq/cpufreq.c | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > > index a09a29c..33f3d65 100644 > > --- a/drivers/cpufreq/cpufreq.c > > +++ b/drivers/cpufreq/cpufreq.c > > @@ -27,6 +27,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > > > @@ -2550,6 +2551,14 @@ int cpufreq_unregister_driver(struct cpufreq_driver *driver) > > } > > EXPORT_SYMBOL_GPL(cpufreq_unregister_driver); > > > > +/* > > + * Stop cpufreq at shutdown to make sure it isn't holding any locks > > + * or mutexes when secondary CPUs are halted. > > + */ > > +static struct syscore_ops cpufreq_syscore_ops = { > > + .shutdown = cpufreq_suspend, > > +}; > > + > > static int __init cpufreq_core_init(void) > > { > > if (cpufreq_disabled()) > > @@ -2558,6 +2567,8 @@ static int __init cpufreq_core_init(void) > > cpufreq_global_kobject = kobject_create(); > > BUG_ON(!cpufreq_global_kobject); > > > > + register_syscore_ops(&cpufreq_syscore_ops); > > + > > return 0; > > } > > core_initcall(cpufreq_core_init); > > Acked-by: Viresh Kumar Queued up for 3.20, thanks! -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.