PM: Handle device registrations during suspend/resume
Modify the PM core to protect its data structures, specifically the
dpm_active list, from being corrupted if a child of the currently
suspending device is registered concurrently with its ->suspend()
callback. In that case, since the new device (the child) is added
to dpm_active after its parent, the PM core will attempt to
suspend it after the parent, which is wrong.
Introduce a new member of struct dev_pm_info, called 'sleeping',
and use it to check if the parent of the device being added to
dpm_active has been suspended, in which case the device registration
fails. Also, use 'sleeping' for checking if the ordering of devices
on dpm_active is correct.
Introduce variable 'all_sleeping' that will be set to 'true' once all
devices have been suspended and make new device registrations fail
until 'all_sleeping' is reset to 'false', in order to avoid having
unsuspended devices around while the system is going into a sleep state.
Remove pm_sleep_rwsem which is not necessary any more.
Special thanks to Alan Stern for discussions and suggestions that
lead to the creation of this patch.
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c
index 26de2c0..0e3991a 100644
--- a/drivers/base/power/main.c
+++ b/drivers/base/power/main.c
@@ -54,7 +54,8 @@
static DEFINE_MUTEX(dpm_list_mtx);
-static DECLARE_RWSEM(pm_sleep_rwsem);
+/* 'true' if all devices have been suspended, protected by dpm_list_mtx */
+static bool all_sleeping;
int (*platform_enable_wakeup)(struct device *dev, int is_on);
@@ -62,14 +63,28 @@
* device_pm_add - add a device to the list of active devices
* @dev: Device to be added to the list
*/
-void device_pm_add(struct device *dev)
+int device_pm_add(struct device *dev)
{
+ int error = 0;
+
pr_debug("PM: Adding info for %s:%s\n",
dev->bus ? dev->bus->name : "No Bus",
kobject_name(&dev->kobj));
mutex_lock(&dpm_list_mtx);
- list_add_tail(&dev->power.entry, &dpm_active);
+ if ((dev->parent && dev->parent->power.sleeping) || all_sleeping) {
+ if (dev->parent->power.sleeping)
+ dev_warn(dev,
+ "parent %s is sleeping, will not add\n",
+ dev->parent->bus_id);
+ else
+ dev_warn(dev, "devices are sleeping, will not add\n");
+ WARN_ON(true);
+ error = -EBUSY;
+ } else {
+ list_add_tail(&dev->power.entry, &dpm_active);
+ }
mutex_unlock(&dpm_list_mtx);
+ return error;
}
/**
@@ -107,32 +122,6 @@
}
EXPORT_SYMBOL_GPL(device_pm_schedule_removal);
-/**
- * pm_sleep_lock - mutual exclusion for registration and suspend
- *
- * Returns 0 if no suspend is underway and device registration
- * may proceed, otherwise -EBUSY.
- */
-int pm_sleep_lock(void)
-{
- if (down_read_trylock(&pm_sleep_rwsem))
- return 0;
-
- return -EBUSY;
-}
-
-/**
- * pm_sleep_unlock - mutual exclusion for registration and suspend
- *
- * This routine undoes the effect of device_pm_add_lock
- * when a device's registration is complete.
- */
-void pm_sleep_unlock(void)
-{
- up_read(&pm_sleep_rwsem);
-}
-
-
/*------------------------- Resume routines -------------------------*/
/**
@@ -242,11 +231,13 @@
static void dpm_resume(void)
{
mutex_lock(&dpm_list_mtx);
+ all_sleeping = false;
while(!list_empty(&dpm_off)) {
struct list_head *entry = dpm_off.next;
struct device *dev = to_device(entry);
list_move_tail(entry, &dpm_active);
+ dev->power.sleeping = false;
mutex_unlock(&dpm_list_mtx);
resume_device(dev);
mutex_lock(&dpm_list_mtx);
@@ -285,7 +276,6 @@
might_sleep();
dpm_resume();
unregister_dropped_devices();
- up_write(&pm_sleep_rwsem);
}
EXPORT_SYMBOL_GPL(device_resume);
@@ -421,6 +411,9 @@
struct list_head *entry = dpm_active.prev;
struct device *dev = to_device(entry);
+ WARN_ON(dev->parent && dev->parent->power.sleeping);
+
+ dev->power.sleeping = true;
mutex_unlock(&dpm_list_mtx);
error = suspend_device(dev, state);
mutex_lock(&dpm_list_mtx);
@@ -432,11 +425,14 @@
(error == -EAGAIN ?
" (please convert to suspend_late)" :
""));
+ dev->power.sleeping = false;
break;
}
if (!list_empty(&dev->power.entry))
list_move(&dev->power.entry, &dpm_off);
}
+ if (!error)
+ all_sleeping = true;
mutex_unlock(&dpm_list_mtx);
return error;
@@ -454,7 +450,6 @@
int error;
might_sleep();
- down_write(&pm_sleep_rwsem);
error = dpm_suspend(state);
if (error)
device_resume();