PM / sleep: prohibit devices probing during suspend/hibernation
It is unsafe [1] 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 in dpm_prepare() and defer their probing instead. The normal behavior will be restored in dpm_complete(). This patch introduces new DD core APIs: device_block_probing() It will disable probing of devices and defer their probes instead. device_unblock_probing() It will restore normal behavior and trigger re-probing of deferred devices. [1] https://lkml.org/lkml/2015/9/11/554 Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com> Acked-by: Pavel Machek <pavel@ucw.cz> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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@ -131,6 +131,8 @@ extern void device_remove_groups(struct device *dev,
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extern char *make_class_name(const char *name, struct kobject *kobj);
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extern int devres_release_all(struct device *dev);
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extern void device_block_probing(void);
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extern void device_unblock_probing(void);
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/* /sys/devices directory */
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extern struct kset *devices_kset;
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@ -54,6 +54,13 @@ static LIST_HEAD(deferred_probe_active_list);
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static struct workqueue_struct *deferred_wq;
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static atomic_t deferred_trigger_count = ATOMIC_INIT(0);
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/*
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* In some cases, like suspend to RAM or hibernation, It might be reasonable
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* to prohibit probing of devices as it could be unsafe.
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* Once defer_all_probes is true all drivers probes will be forcibly deferred.
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*/
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static bool defer_all_probes;
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/*
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* deferred_probe_work_func() - Retry probing devices in the active list.
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*/
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@ -171,6 +178,30 @@ static void driver_deferred_probe_trigger(void)
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queue_work(deferred_wq, &deferred_probe_work);
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}
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/**
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* device_block_probing() - Block/defere device's probes
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*
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* It will disable probing of devices and defer their probes instead.
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*/
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void device_block_probing(void)
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{
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defer_all_probes = true;
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/* sync with probes to avoid races. */
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wait_for_device_probe();
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}
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/**
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* device_unblock_probing() - Unblock/enable device's probes
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*
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* It will restore normal behavior and trigger re-probing of deferred
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* devices.
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*/
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void device_unblock_probing(void)
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{
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defer_all_probes = false;
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driver_deferred_probe_trigger();
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}
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/**
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* deferred_probe_initcall() - Enable probing of deferred devices
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*
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@ -277,9 +308,20 @@ static DECLARE_WAIT_QUEUE_HEAD(probe_waitqueue);
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static int really_probe(struct device *dev, struct device_driver *drv)
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{
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int ret = 0;
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int ret = -EPROBE_DEFER;
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int local_trigger_count = atomic_read(&deferred_trigger_count);
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if (defer_all_probes) {
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/*
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* Value of defer_all_probes can be set only by
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* device_defer_all_probes_enable() which, in turn, will call
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* wait_for_device_probe() right after that to avoid any races.
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*/
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dev_dbg(dev, "Driver %s force probe deferral\n", drv->name);
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driver_deferred_probe_add(dev);
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return ret;
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}
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atomic_inc(&probe_count);
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pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
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drv->bus->name, __func__, drv->name, dev_name(dev));
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@ -393,6 +435,10 @@ int driver_probe_done(void)
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*/
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void wait_for_device_probe(void)
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{
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/* wait for the deferred probe workqueue to finish */
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if (driver_deferred_probe_enable)
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flush_workqueue(deferred_wq);
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/* wait for the known devices to complete their probing */
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wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
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async_synchronize_full();
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@ -963,6 +963,9 @@ void dpm_complete(pm_message_t state)
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}
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list_splice(&list, &dpm_list);
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mutex_unlock(&dpm_list_mtx);
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/* Allow device probing and trigger re-probing of deferred devices */
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device_unblock_probing();
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trace_suspend_resume(TPS("dpm_complete"), state.event, false);
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}
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@ -1624,6 +1627,20 @@ int dpm_prepare(pm_message_t state)
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trace_suspend_resume(TPS("dpm_prepare"), state.event, true);
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might_sleep();
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/*
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* Give a chance for the known devices to complete their probes, before
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* disable probing of devices. This sync point is important at least
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* at boot time + hibernation restore.
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*/
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wait_for_device_probe();
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/*
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* It is unsafe if probing of devices will happen during suspend or
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* hibernation and system behavior will be unpredictable in this case.
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* So, let's prohibit device's probing here and defer their probes
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* instead. The normal behavior will be restored in dpm_complete().
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*/
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device_block_probing();
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mutex_lock(&dpm_list_mtx);
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while (!list_empty(&dpm_list)) {
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struct device *dev = to_device(dpm_list.next);
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