Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v2] cpufreq: suspend cpufreq governors on shutdown | Date | Fri, 30 Jan 2015 01:14:12 +0100 |
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On Monday, December 29, 2014 09:45:42 AM Viresh Kumar wrote: > On 24 December 2014 at 11:39, Doug Anderson <dianders@chromium.org> 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 <dianders@chromium.org> > > --- > > 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 <linux/mutex.h> > > #include <linux/slab.h> > > #include <linux/suspend.h> > > +#include <linux/syscore_ops.h> > > #include <linux/tick.h> > > #include <trace/events/power.h> > > > > @@ -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 <viresh.kumar@linaro.org>
Queued up for 3.20, thanks!
-- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center.
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