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Subject: 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>
---
net/mac80211/debugfs_sta.c | 11 +++++++++++
net/mac80211/sta_info.c | 7 ++++++-
net/mac80211/sta_info.h | 1 +
3 files changed, 18 insertions(+), 1 deletion(-)
--- everything.orig/net/mac80211/debugfs_sta.c 2008-10-07 20:05:29.000000000 +0200
+++ everything/net/mac80211/debugfs_sta.c 2008-10-07 20:06:39.000000000 +0200
@@ -249,11 +249,22 @@ void ieee80211_sta_debugfs_add(struct st
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;
--- everything.orig/net/mac80211/sta_info.c 2008-10-07 20:05:29.000000000 +0200
+++ everything/net/mac80211/sta_info.c 2008-10-07 20:06:39.000000000 +0200
@@ -635,7 +635,12 @@ static void sta_info_debugfs_add_work(st
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;
--- everything.orig/net/mac80211/sta_info.h 2008-10-07 20:05:29.000000000 +0200
+++ everything/net/mac80211/sta_info.h 2008-10-07 20:06:39.000000000 +0200
@@ -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
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