From beffd138d358b69bf15f5a46cb18b31a9b37befb Mon Sep 17 00:00:00 2001 From: Simon Wunderlich Date: Thu, 21 Nov 2013 18:19:52 +0100 Subject: [PATCH] mac80211: don't cancel csa finalize work within stop_ap The current channel switch code has a potential deadlock: 1) * cfg80211_stop_ap acquires wdev-lock * ieee80211_stop_ap calls cancel_work_sync for the csa_finalize_work, which acquires the associated worker-lock 2) * ieee80211_csa_finalize_work holds the worker-lock when run * it calls cfg80211_ch_switch_notify which will claim the wdev-lock, and also needs to claim the sdata-lock (which is the same as the wdev-lock) to modify the beacons. It is sufficient to just set the channel switch active to false. If the worker is running later, it will find the channel switch to not be active anymore and returns immediately without changing anything. Canceling the worker is done anyway when the interface goes down (ieee80211_do_stop). Reported-by: Johannes Berg Signed-off-by: Simon Wunderlich Signed-off-by: Johannes Berg --- net/mac80211/cfg.c | 1 - 1 file changed, 1 deletion(-) diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c index 1d446ac9..a66f4f1 100644 --- a/net/mac80211/cfg.c +++ b/net/mac80211/cfg.c @@ -1080,7 +1080,6 @@ static int ieee80211_stop_ap(struct wiphy *wiphy, struct net_device *dev) /* abort any running channel switch */ sdata->vif.csa_active = false; - cancel_work_sync(&sdata->csa_finalize_work); cancel_work_sync(&sdata->u.ap.request_smps_work); /* turn off carrier for this interface and dependent VLANs */ -- 2.7.4