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authorJohannes Berg <johannes@sipsolutions.net>2008-10-07 12:04:29 +0200
committerJohn W. Linville <linville@tuxdriver.com>2008-10-14 20:46:41 -0400
commit63044e9f54b6bac50d2380bf4d14f63e9e7de72b (patch)
tree9ceddf721c869fb9450429fd4932d8c40b765486
parent45527c2c4f698f8927239cfdec9f515cafed5f10 (diff)
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: Johannes Berg <johannes@sipsolutions.net> Cc: Robin Holt <holt@sgi.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
-rw-r--r--net/mac80211/debugfs_sta.c11
-rw-r--r--net/mac80211/sta_info.c7
-rw-r--r--net/mac80211/sta_info.h1
3 files changed, 18 insertions, 1 deletions
diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c
index b9902e425f0..189d0bafa91 100644
--- a/net/mac80211/debugfs_sta.c
+++ b/net/mac80211/debugfs_sta.c
@@ -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;
diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 9b72d15bc8d..7fef8ea1f5e 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -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;
diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index a6b51862a89..168a39a298b 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -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