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Commit f16bfc1c authored by Johannes Berg's avatar Johannes Berg Committed by David S. Miller
Browse files

[WIRELESS] cfg80211: Clarify locking comment. 



This patch clarifies the comment about locking in wiphy_unregister.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a4d73ee1

net/wireless/core.c

+15 −4
Original line number Diff line number Diff line
@@ -91,7 +91,6 @@ int wiphy_register(struct wiphy *wiphy) 


	mutex_lock(&cfg80211_drv_mutex);





	res = device_add(&drv->wiphy.dev);

	if (res)

		goto out_unlock;
@@ -114,14 +113,26 @@ void wiphy_unregister(struct wiphy *wiphy) 
{

	struct cfg80211_registered_device *drv = wiphy_to_dev(wiphy);



	/* protect the device list */

	mutex_lock(&cfg80211_drv_mutex);



	/* hold registered driver mutex during list removal as well

	 * to make sure no commands are in progress at the moment */

	BUG_ON(!list_empty(&drv->netdev_list));



	/*

	 * Try to grab drv->mtx. If a command is still in progress,

	 * hopefully the driver will refuse it since it's tearing

	 * down the device already. We wait for this command to complete

	 * before unlinking the item from the list.

	 * Note: as codified by the BUG_ON above we cannot get here if

	 * a virtual interface is still associated. Hence, we can only

	 * get to lock contention here if userspace issues a command

	 * that identified the hardware by wiphy index.

	 */

	mutex_lock(&drv->mtx);

	list_del(&drv->list);

	/* unlock again before freeing */

	mutex_unlock(&drv->mtx);



	list_del(&drv->list);

	device_del(&drv->wiphy.dev);

	debugfs_remove(drv->wiphy.debugfsdir);