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>
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 1710c26..9d626ac 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -963,6 +963,9 @@
}
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);
}
@@ -1624,6 +1627,20 @@
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);