From 63044e9f54b6bac50d2380bf4d14f63e9e7de72b Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Tue, 7 Oct 2008 12:04:29 +0200 Subject: [PATCH] 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 Cc: Robin Holt Signed-off-by: John W. Linville --- 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(-) diff --git a/net/mac80211/debugfs_sta.c b/net/mac80211/debugfs_sta.c index b9902e425f09..189d0bafa91a 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 9b72d15bc8dc..7fef8ea1f5ec 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 a6b51862a89d..168a39a298bd 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 -- 2.20.1