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Commit e823407f authored by Ming Lei's avatar Ming Lei Committed by Linus Torvalds
Browse files

pm / runtime: introduce pm_runtime_set_memalloc_noio() 



Introduce the flag memalloc_noio in 'struct dev_pm_info' to help PM core
to teach mm not allocating memory with GFP_KERNEL flag for avoiding
probable deadlock.

As explained in the comment, any GFP_KERNEL allocation inside
runtime_resume() or runtime_suspend() on any one of device in the path
from one block or network device to the root device in the device tree
may cause deadlock, the introduced pm_runtime_set_memalloc_noio() sets
or clears the flag on device in the path recursively.

Signed-off-by: default avatarMing Lei <ming.lei@canonical.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Oliver Neukum <oneukum@suse.de>
Cc: Jiri Kosina <jiri.kosina@suse.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Greg KH <greg@kroah.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Decotigny <david.decotigny@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21caf2fc

drivers/base/power/runtime.c

+70 −0
Original line number Diff line number Diff line
@@ -124,6 +124,76 @@ unsigned long pm_runtime_autosuspend_expiration(struct device *dev) 
}

EXPORT_SYMBOL_GPL(pm_runtime_autosuspend_expiration);



static int dev_memalloc_noio(struct device *dev, void *data)

{

	return dev->power.memalloc_noio;

}



/*

 * pm_runtime_set_memalloc_noio - Set a device's memalloc_noio flag.

 * @dev: Device to handle.

 * @enable: True for setting the flag and False for clearing the flag.

 *

 * Set the flag for all devices in the path from the device to the

 * root device in the device tree if @enable is true, otherwise clear

 * the flag for devices in the path whose siblings don't set the flag.

 *

 * The function should only be called by block device, or network

 * device driver for solving the deadlock problem during runtime

 * resume/suspend:

 *

 *     If memory allocation with GFP_KERNEL is called inside runtime

 *     resume/suspend callback of any one of its ancestors(or the

 *     block device itself), the deadlock may be triggered inside the

 *     memory allocation since it might not complete until the block

 *     device becomes active and the involed page I/O finishes. The

 *     situation is pointed out first by Alan Stern. Network device

 *     are involved in iSCSI kind of situation.

 *

 * The lock of dev_hotplug_mutex is held in the function for handling

 * hotplug race because pm_runtime_set_memalloc_noio() may be called

 * in async probe().

 *

 * The function should be called between device_add() and device_del()

 * on the affected device(block/network device).

 */

void pm_runtime_set_memalloc_noio(struct device *dev, bool enable)

{

	static DEFINE_MUTEX(dev_hotplug_mutex);



	mutex_lock(&dev_hotplug_mutex);

	for (;;) {

		bool enabled;



		/* hold power lock since bitfield is not SMP-safe. */

		spin_lock_irq(&dev->power.lock);

		enabled = dev->power.memalloc_noio;

		dev->power.memalloc_noio = enable;

		spin_unlock_irq(&dev->power.lock);



		/*

		 * not need to enable ancestors any more if the device

		 * has been enabled.

		 */

		if (enabled && enable)

			break;



		dev = dev->parent;



		/*

		 * clear flag of the parent device only if all the

		 * children don't set the flag because ancestor's

		 * flag was set by any one of the descendants.

		 */

		if (!dev || (!enable &&

			     device_for_each_child(dev, NULL,

						   dev_memalloc_noio)))

			break;

	}

	mutex_unlock(&dev_hotplug_mutex);

}

EXPORT_SYMBOL_GPL(pm_runtime_set_memalloc_noio);



/**

 * rpm_check_suspend_allowed - Test whether a device may be suspended.

 * @dev: Device to test.

include/linux/pm.h

+1 −0
Original line number Diff line number Diff line
@@ -537,6 +537,7 @@ struct dev_pm_info { 
	unsigned int		irq_safe:1;

	unsigned int		use_autosuspend:1;

	unsigned int		timer_autosuspends:1;

	unsigned int		memalloc_noio:1;

	enum rpm_request	request;

	enum rpm_status		runtime_status;

	int			runtime_error;

include/linux/pm_runtime.h

+3 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ extern void pm_runtime_set_autosuspend_delay(struct device *dev, int delay); 
extern unsigned long pm_runtime_autosuspend_expiration(struct device *dev);

extern void pm_runtime_update_max_time_suspended(struct device *dev,

						 s64 delta_ns);

extern void pm_runtime_set_memalloc_noio(struct device *dev, bool enable);



static inline bool pm_children_suspended(struct device *dev)

{
@@ -156,6 +157,8 @@ static inline void pm_runtime_set_autosuspend_delay(struct device *dev, 
						int delay) {}

static inline unsigned long pm_runtime_autosuspend_expiration(

				struct device *dev) { return 0; }

static inline void pm_runtime_set_memalloc_noio(struct device *dev,

						bool enable){}



#endif /* !CONFIG_PM_RUNTIME */