It is unsafe [1] if probing of devices will happen during suspend or hibernation and system behavior will be unpredictable in this case. So, lets 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 API device_defer_all_probes(bool enable) to enable/disable probing of devices: if @enable = true It will disable probing of devices and defer their probes. otherwise It will restore normal behavior and trigger re-probing of deferred devices. [1] https://lkml.org/lkml/2015/9/11/554 Cc: Alan Stern <[email protected]> Cc: Rafael J. Wysocki <[email protected]> Cc: Thierry Reding <[email protected]> Signed-off-by: Grygorii Strashko <[email protected]> --- drivers/base/base.h | 1 + drivers/base/dd.c | 35 ++++++++++++++++++++++++++++++++++- drivers/base/power/main.c | 13 +++++++++++++ 3 files changed, 48 insertions(+), 1 deletion(-) diff --git a/drivers/base/base.h b/drivers/base/base.h index 1782f3a..6c9684b 100644 --- a/drivers/base/base.h +++ b/drivers/base/base.h @@ -131,6 +131,7 @@ 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(bool enable); /* /sys/devices directory */ extern struct kset *devices_kset; diff --git a/drivers/base/dd.c b/drivers/base/dd.c index 98de1a5..d600c14 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 +179,26 @@ static void driver_deferred_probe_trigger(void) } /** + * device_defer_all_probes() - Enable/disable probing of devices + * @enable: Enable/disable probing of devices + * + * if @enable = true + * It will disable probing of devices and defer their probes. + * otherwise + * It will restore normal behavior and trigger re-probing of deferred + * devices. + */ +void device_defer_all_probes(bool enable) +{ + defer_all_probes = enable; + if (enable) + /* sync with probes to avoid any races. */ + wait_for_device_probe(); + else + 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 +304,15 @@ 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) { + 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)); diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c index 1710c26..98c1da36 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(false); trace_suspend_resume(TPS("dpm_complete"), state.event, false); } @@ -1624,6 +1627,16 @@ 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 probing. */ + 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, lets prohibit device's probing here and defer their probes + * instead. The normal behavior will be restored in dpm_complete(). + */ + device_defer_all_probes(true); + mutex_lock(&dpm_list_mtx); while (!list_empty(&dpm_list)) { struct device *dev = to_device(dpm_list.next); -- 2.5.1 -- 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/
