mac80211: handle sched_scan_stopped vs. hw restart race

On hw restart, mac80211 might try to reconfigure already
stopped sched scan, if ieee80211_sched_scan_stopped_work()
wasn't scheduled yet.

This in turn will keep the device driver with scheduled scan
configured, while both mac80211 and cfg80211 will clear
their sched scan state once the work is scheduled.

Fix it by ignoring ieee80211_sched_scan_stopped() calls
while in hw restart, and flush the work before starting
the reconfiguration.

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -248,6 +248,7 @@ static void ieee80211_restart_work(struct work_struct *work)
 
 	/* wait for scan work complete */
 	flush_workqueue(local->workqueue);
+	flush_work(&local->sched_scan_stopped_work);
 
 	WARN(test_bit(SCAN_HW_SCANNING, &local->scanning),
 	     "%s called with hardware scan in progress\n", __func__);

net/mac80211/scan.c

@@ -1213,6 +1213,14 @@ void ieee80211_sched_scan_stopped(struct ieee80211_hw *hw)
 
 	trace_api_sched_scan_stopped(local);
 
+	/*
+	 * this shouldn't really happen, so for simplicity
+	 * simply ignore it, and let mac80211 reconfigure
+	 * the sched scan later on.
+	 */
+	if (local->in_reconfig)
+		return;
+
 	schedule_work(&local->sched_scan_stopped_work);
 }
 EXPORT_SYMBOL(ieee80211_sched_scan_stopped);