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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 <johannes@sipsolutions.net>
Signed-off-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Simon Wunderlich 2013-11-21 18:19:52 +01:00 committed by Johannes Berg
parent e487eaeb07
commit beffd138d3
1 changed files with 0 additions and 1 deletions
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1
net/mac80211/cfg.c
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@ -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 */