From rjw@sisk.pl Thu Mar 13 13:44:50 2008 From: "Rafael J. Wysocki" Date: Wed, 12 Mar 2008 00:57:22 +0100 Subject: PM: Handle device registrations during suspend/resume To: Greg KH Cc: Alan Stern , Andrew Morton , David Brownell , LKML , Pavel Machek , pm list Message-ID: <200803120057.23101.rjw@sisk.pl> Content-Disposition: inline From: Rafael J. Wysocki 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 Acked-by: Pavel Machek Signed-off-by: Greg Kroah-Hartman --- Documentation/power/devices.txt | 5 +++ drivers/base/core.c | 6 +++- drivers/base/power/main.c | 57 ++++++++++++++++++---------------------- drivers/base/power/power.h | 23 ++-------------- include/linux/pm.h | 1 5 files changed, 40 insertions(+), 52 deletions(-) --- a/Documentation/power/devices.txt +++ b/Documentation/power/devices.txt @@ -196,6 +196,11 @@ its parent; and can't be removed or susp The policy is that the device tree should match hardware bus topology. (Or at least the control bus, for devices which use multiple busses.) +In particular, this means that a device registration may fail if the parent of +the device is suspending (ie. has been chosen by the PM core as the next +device to suspend) or has already suspended, as well as after all of the other +devices have been suspended. Device drivers must be prepared to cope with such +situations. Suspending Devices --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -820,7 +820,11 @@ int device_add(struct device *dev) error = dpm_sysfs_add(dev); if (error) goto PMError; - device_pm_add(dev); + error = device_pm_add(dev); + if (error) { + dpm_sysfs_remove(dev); + goto PMError; + } error = bus_add_device(dev); if (error) goto BusError; --- a/drivers/base/power/main.c +++ b/drivers/base/power/main.c @@ -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 dev * 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 d } 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 * 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 stat 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 stat (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(); --- a/drivers/base/power/power.h +++ b/drivers/base/power/power.h @@ -11,30 +11,13 @@ static inline struct device *to_device(s return container_of(entry, struct device, power.entry); } -extern void device_pm_add(struct device *); +extern int device_pm_add(struct device *); extern void device_pm_remove(struct device *); -extern int pm_sleep_lock(void); -extern void pm_sleep_unlock(void); #else /* CONFIG_PM_SLEEP */ - -static inline void device_pm_add(struct device *dev) -{ -} - -static inline void device_pm_remove(struct device *dev) -{ -} - -static inline int pm_sleep_lock(void) -{ - return 0; -} - -static inline void pm_sleep_unlock(void) -{ -} +static inline int device_pm_add(struct device *dev) { return 0; } +static inline void device_pm_remove(struct device *dev) {} #endif --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -183,6 +183,7 @@ typedef struct pm_message { struct dev_pm_info { pm_message_t power_state; unsigned can_wakeup:1; + bool sleeping:1; /* Owned by the PM core */ #ifdef CONFIG_PM_SLEEP unsigned should_wakeup:1; struct list_head entry;