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Commit 63044e9f authored by Johannes Berg's avatar Johannes Berg Committed by John W. Linville
Browse files

mac80211: fix debugfs lockup 



When debugfs_create_dir fails, sta_info_debugfs_add_work will not
terminate because it will find the same station again and again.
This is possible whenever debugfs fails for whatever reason; one
reason is a race condition in mac80211, unfortunately we cannot
do much about it, so just document it, it just means some station
may be missing from debugfs.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 45527c2c

net/mac80211/debugfs_sta.c

+11 −0
Original line number Diff line number Diff line
@@ -249,11 +249,22 @@ void ieee80211_sta_debugfs_add(struct sta_info *sta) 
	DECLARE_MAC_BUF(mbuf);

	u8 *mac;



	sta->debugfs.add_has_run = true;



	if (!stations_dir)

		return;



	mac = print_mac(mbuf, sta->sta.addr);



	/*

	 * This might fail due to a race condition:

	 * When mac80211 unlinks a station, the debugfs entries

	 * remain, but it is already possible to link a new

	 * station with the same address which triggers adding

	 * it to debugfs; therefore, if the old station isn't

	 * destroyed quickly enough the old station's debugfs

	 * dir might still be around.

	 */

	sta->debugfs.dir = debugfs_create_dir(mac, stations_dir);

	if (!sta->debugfs.dir)

		return;

net/mac80211/sta_info.c

+6 −1
Original line number Diff line number Diff line
@@ -635,7 +635,12 @@ static void sta_info_debugfs_add_work(struct work_struct *work) 


		spin_lock_irqsave(&local->sta_lock, flags);

		list_for_each_entry(tmp, &local->sta_list, list) {

			if (!tmp->debugfs.dir) {

			/*

			 * debugfs.add_has_run will be set by

			 * ieee80211_sta_debugfs_add regardless

			 * of what else it does.

			 */

			if (!tmp->debugfs.add_has_run) {

				sta = tmp;

				__sta_info_pin(sta);

				break;

net/mac80211/sta_info.h

+1 −0
Original line number Diff line number Diff line
@@ -300,6 +300,7 @@ struct sta_info { 
		struct dentry *inactive_ms;

		struct dentry *last_seq_ctrl;

		struct dentry *agg_status;

		bool add_has_run;

	} debugfs;

#endif