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[WIRELESS] cfg80211: Clarify locking comment.

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This patch clarifies the comment about locking in wiphy_unregister.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Johannes Berg 2007-04-26 20:51:12 -07:00 committed by David S. Miller
parent a4d73ee168
commit f16bfc1c09
1 changed files with 15 additions and 4 deletions
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19
net/wireless/core.c
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@ -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);