Re: [PATCH v2] PM / sleep: prohibit devices probing during suspend/hibernation

[Grygorii Strashko]

On 11/06/2015 02:13 AM, Rafael J. Wysocki wrote:
> On Thursday, November 05, 2015 11:19:03 PM Pavel Machek wrote:
> > On Mon 2015-10-19 23:54:24, Grygorii Strashko wrote:
> > > It is unsafe [1] if probing of devices will happen during suspend or
> > > hibernation and system behavior will be unpredictable in this case
> > > (for example: after successful probe the device potentially has a different
> > >   set of PM callbacks than before [2]).
> > > So, let's prohibit device's probing in dpm_prepare() and defer their
> > > probes instead. The normal behavior will be restored in dpm_complete().
> > >
> > > This patch introduces new DD core APIs:
> > >   device_defer_all_probes_enable()
> > >     It will disable probing of devices and defer their probes.
> > >   device_defer_all_probes_disable()
> > >     It will restore normal behavior and trigger re-probing of deferred
> > >     devices.
> > >
> > > [1] https://lkml.org/lkml/2015/9/11/554
> > > [2] https://lkml.org/lkml/2015/9/15/1039
> > > Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> > > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
> > > Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
> > > Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > > ---
> > > Changes in v2:
> > > - DD core API device_defer_all_probes(bool enable) split on two
> > >    void device_defer_all_probes_enable(void);
> > >    void device_defer_all_probes_disable(void);
> > > - more comments added
> > >
> > > Link on v1:
> > > - https://lkml.org/lkml/2015/10/8/681
> > >
> > >   drivers/base/base.h       |  2 ++
> > >   drivers/base/dd.c         | 48 ++++++++++++++++++++++++++++++++++++++++++++++-
> > >   drivers/base/power/main.c | 17 +++++++++++++++++
> > >   3 files changed, 66 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/base/base.h b/drivers/base/base.h
> > > index 1782f3a..c332b68 100644
> > > --- a/drivers/base/base.h
> > > +++ b/drivers/base/base.h
> > > @@ -131,6 +131,8 @@ extern void device_remove_groups(struct device *dev,
> > >   extern char *make_class_name(const char *name, struct kobject *kobj);
> > >
> > >   extern int devres_release_all(struct device *dev);
> > > +extern void device_defer_all_probes_enable(void);
> > > +extern void device_defer_all_probes_disable(void);
> > >
> > >   /* /sys/devices directory */
> > >   extern struct kset *devices_kset;
> > > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > > index be0eb46..b8d9e70 100644
> > > --- a/drivers/base/dd.c
> > > +++ b/drivers/base/dd.c
> > > @@ -55,6 +55,13 @@ static struct workqueue_struct *deferred_wq;
> > >   static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
> > >
> > >   /*
> > > + * In some cases, like suspend to RAM or hibernation, It might be reasonable
> > > + * to prohibit probing of devices as it could be unsafe.
> > > + * Once defer_all_probes is true all drivers probes will be forcibly deferred.
> > > + */
> > > +static bool defer_all_probes;
> > > +
> > > +/*
> > >    * deferred_probe_work_func() - Retry probing devices in the active list.
> > >    */
> > >   static void deferred_probe_work_func(struct work_struct *work)
> > > @@ -172,6 +179,30 @@ static void driver_deferred_probe_trigger(void)
> > >   }
> > >
> > >   /**
> > > + * device_defer_all_probes_enable() - Enable deferring of device's probes
> > > + *
> > > + *	It will disable probing of devices and defer their probes.
> > > + */
> > > +void device_defer_all_probes_enable(void)
> > > +{
> > > +	defer_all_probes = true;
> > > +	/* sync with probes to avoid races. */
> > > +	wait_for_device_probe();
> > > +}
> >
> > device_pause_probing()?

device_stop_probing(). Right?

> > > +/**
> > > + * device_defer_all_probes_disable() - Disable deferring of device's probes
> > > + *
> > > + *	It will restore normal behavior and trigger re-probing of deferred
> > > + * devices.
> > > + */

device_start_probing(). Right?

> > Hmm. This is not quite a double negative... but it sounds like one.
> >
> > device_restart_probing()?
>
> I _start/_stop would be fine by me too.

Ok. So do I need rename/resend it again?
Probably, I'll need to wait for -rc1 before resending.

--
regards,
-grygorii
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