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mac80211: fix debugfs lockup

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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: Johannes Berg <johannes@sipsolutions.net>
Cc: Robin Holt <holt@sgi.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Johannes Berg 2008-10-07 12:04:29 +02:00 committed by John W. Linville
parent 45527c2c4f
commit 63044e9f54
3 changed files with 18 additions and 1 deletions
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11
net/mac80211/debugfs_sta.c
View File

@ -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;

7
net/mac80211/sta_info.c
View File

@ -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;

1
net/mac80211/sta_info.h
View File

@ -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