From: "Strashko, Grygorii" grygorii.strashko@ti.com

[ Upstream commit 013c074f8642d8e815ad670601f8e27155a74b57 ]

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 Signed-off-by: Chunyan Zhang zhang.chunyan@linaro.org --- 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..e05db38 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_block_probing(void); +extern void device_unblock_probing(void);

/* /sys/devices directory */ extern struct kset *devices_kset; diff --git a/drivers/base/dd.c b/drivers/base/dd.c index d888741..ddee3456 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_block_probing() - Block/defere device's probes + * + * It will disable probing of devices and defer their probes instead. + */ +void device_block_probing(void) +{ + defer_all_probes = true; + /* sync with probes to avoid races. */ + wait_for_device_probe(); +} + +/** + * device_unblock_probing() - Unblock/enable device's probes + * + * It will restore normal behavior and trigger re-probing of deferred + * devices. + */ +void device_unblock_probing(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. @@ -279,9 +310,20 @@ 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)); @@ -387,6 +429,10 @@ 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 6c5bc3f..cf4384d 100644 --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -966,6 +966,9 @@ 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_unblock_probing(); trace_suspend_resume(TPS("dpm_complete"), state.event, false); }

@@ -1638,6 +1641,20 @@ 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_block_probing(); + mutex_lock(&dpm_list_mtx); while (!list_empty(&dpm_list)) { struct device *dev = to_device(dpm_list.next);