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Commit a994a9ee authored by Saravana Kannan's avatar Saravana Kannan
Browse files

FROMGIT: driver core: Allow device link operations inside sync_state() 



Some sync_state() implementations might need to call APIs that in turn
make calls to device link APIs. So, do the sync_state() callbacks
without holding the device link lock.

Signed-off-by: default avatarSaravana Kannan <saravanak@google.com>
Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20191114225646.251277-1-saravanak@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry-pick from commit 26e77708fdc20ec6c24759602640ac42b8e4e88a
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git driver-core-next)
Change-Id: I0787645c410137f9f91fb808675ccf7dd1b5a7c0
parent 1e77e130

drivers/base/core.c

+71 −8
Original line number Diff line number Diff line
@@ -553,7 +553,26 @@ int device_links_check_suppliers(struct device *dev) 
	return ret;

}



static void __device_links_supplier_sync_state(struct device *dev)

/**

 * __device_links_queue_sync_state - Queue a device for sync_state() callback

 * @dev: Device to call sync_state() on

 * @list: List head to queue the @dev on

 *

 * Queues a device for a sync_state() callback when the device links write lock

 * isn't held. This allows the sync_state() execution flow to use device links

 * APIs.  The caller must ensure this function is called with

 * device_links_write_lock() held.

 *

 * This function does a get_device() to make sure the device is not freed while

 * on this list.

 *

 * So the caller must also ensure that device_links_flush_sync_list() is called

 * as soon as the caller releases device_links_write_lock().  This is necessary

 * to make sure the sync_state() is called in a timely fashion and the

 * put_device() is called on this device.

 */

static void __device_links_queue_sync_state(struct device *dev,

					    struct list_head *list)

{

	struct device_link *link;
@@ -567,12 +586,45 @@ static void __device_links_supplier_sync_state(struct device *dev) 
			return;

	}



	/*

	 * Set the flag here to avoid adding the same device to a list more

	 * than once. This can happen if new consumers get added to the device

	 * and probed before the list is flushed.

	 */

	dev->state_synced = true;



	if (WARN_ON(!list_empty(&dev->links.defer_sync)))

		return;



	get_device(dev);

	list_add_tail(&dev->links.defer_sync, list);

}



/**

 * device_links_flush_sync_list - Call sync_state() on a list of devices

 * @list: List of devices to call sync_state() on

 *

 * Calls sync_state() on all the devices that have been queued for it. This

 * function is used in conjunction with __device_links_queue_sync_state().

 */

static void device_links_flush_sync_list(struct list_head *list)

{

	struct device *dev, *tmp;



	list_for_each_entry_safe(dev, tmp, list, links.defer_sync) {

		list_del_init(&dev->links.defer_sync);



		device_lock(dev);



		if (dev->bus->sync_state)

			dev->bus->sync_state(dev);

		else if (dev->driver && dev->driver->sync_state)

			dev->driver->sync_state(dev);



	dev->state_synced = true;

		device_unlock(dev);



		put_device(dev);

	}

}



void device_links_supplier_sync_state_pause(void)
@@ -585,6 +637,7 @@ void device_links_supplier_sync_state_pause(void) 
void device_links_supplier_sync_state_resume(void)

{

	struct device *dev, *tmp;

	LIST_HEAD(sync_list);



	device_links_write_lock();

	if (!defer_sync_state_count) {
@@ -596,11 +649,17 @@ void device_links_supplier_sync_state_resume(void) 
		goto out;



	list_for_each_entry_safe(dev, tmp, &deferred_sync, links.defer_sync) {

		__device_links_supplier_sync_state(dev);

		/*

		 * Delete from deferred_sync list before queuing it to

		 * sync_list because defer_sync is used for both lists.

		 */

		list_del_init(&dev->links.defer_sync);

		__device_links_queue_sync_state(dev, &sync_list);

	}

out:

	device_links_write_unlock();



	device_links_flush_sync_list(&sync_list);

}



static int sync_state_resume_initcall(void)
@@ -630,6 +689,7 @@ static void __device_links_supplier_defer_sync(struct device *sup) 
void device_links_driver_bound(struct device *dev)

{

	struct device_link *link;

	LIST_HEAD(sync_list);



	/*

	 * If a device probes successfully, it's expected to have created all
@@ -660,12 +720,15 @@ void device_links_driver_bound(struct device *dev) 
		if (defer_sync_state_count)

			__device_links_supplier_defer_sync(link->supplier);

		else

			__device_links_supplier_sync_state(link->supplier);

			__device_links_queue_sync_state(link->supplier,

							&sync_list);

	}



	dev->links.status = DL_DEV_DRIVER_BOUND;



	device_links_write_unlock();



	device_links_flush_sync_list(&sync_list);

}



/**