On Monday, October 19, 2015 11:54:24 PM 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 <[email protected]> > Cc: Rafael J. Wysocki <[email protected]> > Cc: Thierry Reding <[email protected]> > Signed-off-by: Grygorii Strashko <[email protected]>
Greg, any objections against this one? > --- > 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_defer_all_probes_disable() - Disable deferring of device's probes > + * > + * It will restore normal behavior and trigger re-probing of deferred > + * devices. > + */ > +void device_defer_all_probes_disable(void) > +{ > + defer_all_probes = false; > + driver_deferred_probe_trigger(); > +} > + > +/** > * deferred_probe_initcall() - Enable probing of deferred devices > * > * We don't want to get in the way when the bulk of drivers are getting > probed. > @@ -277,9 +308,20 @@ static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue); > > static int really_probe(struct device *dev, struct device_driver *drv) > { > - int ret = 0; > + int ret = -EPROBE_DEFER; > int local_trigger_count = atomic_read(&deferred_trigger_count); > > + if (defer_all_probes) { > + /* > + * Value of defer_all_probes can be set only by > + * device_defer_all_probes_enable() which, in turn, will call > + * wait_for_device_probe() right after that to avoid any races. > + */ > + dev_dbg(dev, "Driver %s force probe deferral\n", drv->name); > + driver_deferred_probe_add(dev); > + return ret; > + } > + > atomic_inc(&probe_count); > pr_debug("bus: '%s': %s: probing driver %s with device %s\n", > drv->bus->name, __func__, drv->name, dev_name(dev)); > @@ -391,6 +433,10 @@ int driver_probe_done(void) > */ > void wait_for_device_probe(void) > { > + /* wait for the deferred probe workqueue to finish */ > + if (driver_deferred_probe_enable) > + flush_workqueue(deferred_wq); > + > /* wait for the known devices to complete their probing */ > wait_event(probe_waitqueue, atomic_read(&probe_count) == 0); > async_synchronize_full(); > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index 1710c26..eeb2bb7 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -963,6 +963,9 @@ void dpm_complete(pm_message_t state) > } > list_splice(&list, &dpm_list); > mutex_unlock(&dpm_list_mtx); > + > + /* Allow device probing and trigger re-probing of deferred devices */ > + device_defer_all_probes_disable(); > trace_suspend_resume(TPS("dpm_complete"), state.event, false); > } > > @@ -1624,6 +1627,20 @@ int dpm_prepare(pm_message_t state) > trace_suspend_resume(TPS("dpm_prepare"), state.event, true); > might_sleep(); > > + /* > + * Give a chance for the known devices to complete their probes, before > + * disable probing of devices. This sync point is important at least > + * at boot time + hibernation restore. > + */ > + wait_for_device_probe(); > + /* > + * It is unsafe if probing of devices will happen during suspend or > + * hibernation and system behavior will be unpredictable in this case. > + * So, let's prohibit device's probing here and defer their probes > + * instead. The normal behavior will be restored in dpm_complete(). > + */ > + device_defer_all_probes_enable(); > + > mutex_lock(&dpm_list_mtx); > while (!list_empty(&dpm_list)) { > struct device *dev = to_device(dpm_list.next); > Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
