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PM: Handle device registrations during suspend/resume

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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>
This commit is contained in:
Rafael J. Wysocki
2008-03-12 00:57:22 +01:00
committed by Greg Kroah-Hartman
parent 6bcf19d02a
commit 58aca23226
5 changed files with 40 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

57
drivers/base/power/main.c
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@@ -54,7 +54,8 @@ static LIST_HEAD(dpm_destroy);
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 @@ int (*platform_enable_wakeup)(struct device *dev, int is_on);
* 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 @@ void device_pm_schedule_removal(struct device *dev)
}
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 int resume_device(struct device *dev)
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 @@ void device_resume(void)
might_sleep();
dpm_resume();
unregister_dropped_devices();
up_write(&pm_sleep_rwsem);
}
EXPORT_SYMBOL_GPL(device_resume);
@@ -421,6 +411,9 @@ static int dpm_suspend(pm_message_t state)
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 @@ static int dpm_suspend(pm_message_t state)
(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 device_suspend(pm_message_t state)
int error;
might_sleep();
down_write(&pm_sleep_rwsem);
error = dpm_suspend(state);
if (error)
device_resume();