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    SubjectRe: [PATCH v2] PM / sleep: prohibit devices probing during suspend/hibernation
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    On Friday, November 06, 2015 11:58:40 AM Grygorii Strashko wrote:
    > 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@rowland.harvard.edu>
    > >>> Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
    > >>> Cc: Thierry Reding <thierry.reding@gmail.com>
    > >>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
    > >>> ---
    > >>> 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?

    Or device_block_probing()

    > >>
    > >>> +/**
    > >>> + * 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?

    and device_unblock_probing()

    >
    > >>
    > >> 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?

    Yes, please.

    > Probably, I'll need to wait for -rc1 before resending.

    No, you don't. Please resend when you're ready.

    Thanks,
    Rafael



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