dpm_list currently relies on the fact that child devices will be registered after their parents to get a correct suspend order. However, using device_move() destroys this assumption, as an already registered device may be moved under a newly registered one. This problem was discussed in the thread starting at https://lists.linux-foundation.org/pipermail/linux-pm/2007-July/014428.html The consensus seemed to be that it would be best if drivers were offered a set of function for manipulating dpm_list. This patch does the following: - Export device_pm_{lock,unlock} so that drivers may lock the dpm_list in order to avoid races. - Introduce device_pm_move_*() functions that manipulate dpm_list. Those function must be called with the dpm_list mutex held. Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx> --- drivers/base/core.c | 4 ++ drivers/base/power/main.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++ include/linux/pm.h | 19 ++++++++++++ 3 files changed, 91 insertions(+) --- linux-2.6.orig/drivers/base/power/main.c +++ linux-2.6/drivers/base/power/main.c @@ -32,6 +32,9 @@ * because children are guaranteed to be discovered after parents, and * are inserted at the back of the list on discovery. * + * However, since device_move() destroys this assumption, callers + * need to fix up the dpm_list if they use device_move(). + * * Since device_pm_add() may be called with a device semaphore held, * we must never try to acquire a device semaphore while holding * dpm_list_mutex. @@ -54,6 +57,7 @@ void device_pm_lock(void) { mutex_lock(&dpm_list_mtx); } +EXPORT_SYMBOL_GPL(device_pm_lock); /** * device_pm_unlock - unlock the list of active devices used by the PM core @@ -62,6 +66,7 @@ void device_pm_unlock(void) { mutex_unlock(&dpm_list_mtx); } +EXPORT_SYMBOL_GPL(device_pm_unlock); /** * device_pm_add - add a device to the list of active devices @@ -107,6 +112,69 @@ void device_pm_remove(struct device *dev } /** + * device_pm_move_before - move device in dpm_list + * @deva: Device to move in dpm_list + * @devb: Device @deva should come before + * + * The purpose of this function is to allow reordering of + * dpm_list after calling device_move(). + * Callers need to hold the dpm_list mutex. + */ +void device_pm_move_before(struct device *deva, struct device *devb) +{ + BUG_ON(!mutex_is_locked(&dpm_list_mtx)); + pr_debug("PM: Moving %s:%s before %s:%s\n", + deva->bus ? deva->bus->name : "No Bus", + kobject_name(&deva->kobj), + devb->bus ? devb->bus->name : "No Bus", + kobject_name(&devb->kobj)); + /* Delete deva from dpm_list and reinsert before devb. */ + list_move_tail(&deva->power.entry, &devb->power.entry); +} +EXPORT_SYMBOL_GPL(device_pm_move_before); + +/** + * device_pm_move_after - move device in dpm_list + * @deva: Device to move in dpm_list + * @devb: Device @deva should come after + * + * The purpose of this function is to allow reordering of + * dpm_list after calling device_move(). + * Callers need to hold the dpm_list mutex. + */ +void device_pm_move_after(struct device *deva, struct device *devb) +{ + BUG_ON(!mutex_is_locked(&dpm_list_mtx)); + pr_debug("PM: Moving %s:%s after %s:%s\n", + deva->bus ? deva->bus->name : "No Bus", + kobject_name(&deva->kobj), + devb->bus ? devb->bus->name : "No Bus", + kobject_name(&devb->kobj)); + /* Delete deva from dpm_list and reinsert after devb. */ + list_move(&deva->power.entry, &devb->power.entry); +} +EXPORT_SYMBOL_GPL(device_pm_move_after); + +/** + * device_pm_move_last - move device to end of dpm_list + * @dev: Device to move in dpm_list + * + * The purpose of this function is to allow reordering of + * dpm_list after calling device_move(). + * Callers need to hold the dpm_list mutex. + * @dev must not have any children. + */ +void device_pm_move_last(struct device *dev) +{ + BUG_ON(!mutex_is_locked(&dpm_list_mtx)); + pr_debug("PM: Moving %s:%s to end of list\n", + dev->bus ? dev->bus->name : "No Bus", + kobject_name(&dev->kobj)); + list_move(&dev->power.entry, &dpm_list); +} +EXPORT_SYMBOL_GPL(device_pm_move_last); + +/** * pm_op - execute the PM operation appropiate for given PM event * @dev: Device. * @ops: PM operations to choose from. --- linux-2.6.orig/include/linux/pm.h +++ linux-2.6/include/linux/pm.h @@ -398,15 +398,34 @@ extern void __suspend_report_result(cons __suspend_report_result(__func__, fn, ret); \ } while (0) +extern void device_pm_move_before(struct device *deva, struct device *devb); +extern void device_pm_move_after(struct device *deva, struct device *devb); +extern void device_pm_move_last(struct device *dev); #else /* !CONFIG_PM_SLEEP */ +#define device_pm_lock() do {} while (0) static inline int device_suspend(pm_message_t state) { return 0; } +#define device_pm_unlock() do {} while (0) + #define suspend_report_result(fn, ret) do {} while (0) +static inline void device_pm_move_before(struct device *deva, + struct device *devb) +{ +} + +static inline void device_pm_move_after(struct device *deva, + struct device *devb) +{ +} + +static inline void device_pm_move_last(struct device *dev) +{ +} #endif /* !CONFIG_PM_SLEEP */ /* --- linux-2.6.orig/drivers/base/core.c +++ linux-2.6/drivers/base/core.c @@ -1563,6 +1563,10 @@ out: * device_move - moves a device to a new parent * @dev: the pointer to the struct device to be moved * @new_parent: the new parent of the device (can by NULL) + * + * Note: device_move() does not change the ancestral order as reflected + * in dpm_list; you will need to do it yourself using the device_pm_move_* + * functions. */ int device_move(struct device *dev, struct device *new_parent) { _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
