mac80211: assure we also cancel deferred scan request

This is partial revert and fix for commit
85f72bc839 "mac80211: only cancel
software-based scans on suspend"

When cfg80211 request the scan and mac80211 perform some management work,
we defer the scan request. We do not canceling such requests when calling
ieee80211_scan_cancel(), because of SCAN_SW_SCANNING bit check just
before the call. So fix that problem.

Another problem, which commit 85f72bc839
tries to solve, is we can not cancel HW scan. Hence patch make
ieee80211_scan_cancel() ignore HW scan (see code comments). Keeping
local->mtx lock assures that the deferred scan will not become
"working" HW scan.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/main.c

@@ -307,8 +307,7 @@ static void ieee80211_restart_work(struct work_struct *work)
 	mutex_unlock(&local->mtx);
 
 	rtnl_lock();
-	if (unlikely(test_bit(SCAN_SW_SCANNING, &local->scanning)))
-		ieee80211_scan_cancel(local);
+	ieee80211_scan_cancel(local);
 	ieee80211_reconfig(local);
 	rtnl_unlock();
 }

net/mac80211/pm.c

@@ -12,8 +12,7 @@ int __ieee80211_suspend(struct ieee80211_hw *hw)
 	struct ieee80211_sub_if_data *sdata;
 	struct sta_info *sta;
 
-	if (unlikely(test_bit(SCAN_SW_SCANNING, &local->scanning)))
-		ieee80211_scan_cancel(local);
+	ieee80211_scan_cancel(local);
 
 	ieee80211_stop_queues_by_reason(hw,
 			IEEE80211_QUEUE_STOP_REASON_SUSPEND);

net/mac80211/scan.c

@@ -793,24 +793,39 @@ int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
 	return ret;
 }
 
+/*
+ * Only call this function when a scan can't be queued -- under RTNL.
+ */
 void ieee80211_scan_cancel(struct ieee80211_local *local)
 {
-	bool abortscan;
-	bool finish = false;
-
-	cancel_delayed_work_sync(&local->scan_work);
+	bool abortscan, finish;
 
 	/*
-	 * Only call this function when a scan can't be
-	 * queued -- mostly at suspend under RTNL.
+	 * We are only canceling software scan, or deferred scan that was not
+	 * yet really started (see __ieee80211_start_scan ).
+	 *
+	 * Regarding hardware scan:
+	 * - we can not call  __ieee80211_scan_completed() as when
+	 *   SCAN_HW_SCANNING bit is set this function change
+	 *   local->hw_scan_req to operate on 5G band, what race with
+	 *   driver which can use local->hw_scan_req
+	 *
+	 * - we can not cancel scan_work since driver can schedule it
+	 *   by ieee80211_scan_completed(..., true) to finish scan
+	 *
+	 * Hence low lever driver is responsible for canceling HW scan.
 	 */
+
 	mutex_lock(&local->mtx);
-	abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) ||
-		    (!local->scanning && local->scan_req);
+	abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning);
 	if (abortscan)
 		finish = __ieee80211_scan_completed(&local->hw, true, false);
 	mutex_unlock(&local->mtx);
 
-	if (finish)
-		__ieee80211_scan_completed_finish(&local->hw, false);
+	if (abortscan) {
+		/* The scan is canceled, but stop work from being pending */
+		cancel_delayed_work_sync(&local->scan_work);
+		if (finish)
+			__ieee80211_scan_completed_finish(&local->hw, false);
+	}
 }