mac80211: redefine usage of the mac80211 workqueue

The mac80211 workqueue exists to enable mac80211 and drivers
to queue their own work on a single threaded workqueue. mac80211
takes care to flush the workqueue during suspend but we never
really had requirements on drivers for how they should use
the workqueue in consideration for suspend.

We extend mac80211 to document how the mac80211 workqueue should
be used, how it should not be used and finally move raw access to
the workqueue to mac80211 only. Drivers and mac80211 use helpers
to queue work onto the mac80211 workqueue:

  * ieee80211_queue_work()
  * ieee80211_queue_delayed_work()

These helpers will now warn if mac80211 already completed its
suspend cycle and someone is trying to queue work. mac80211
flushes the mac80211 workqueue prior to suspend a few times,
but we haven't taken the care to ensure drivers won't add more
work after suspend. To help with this we add a warning when
someone tries to add work and mac80211 already completed the
suspend cycle.

Drivers should ensure they cancel any work or delayed work
in the mac80211 stop() callback.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 41 insertions, 0 deletions

diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 8502936..e55d57f 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -511,6 +511,46 @@ void ieee80211_iterate_active_interfaces_atomic(
 }
 EXPORT_SYMBOL_GPL(ieee80211_iterate_active_interfaces_atomic);
 
+/*
+ * Nothing should have been stuffed into the workqueue during
+ * the suspend->resume cycle. If this WARN is seen then there
+ * is a bug with either the driver suspend or something in
+ * mac80211 stuffing into the workqueue which we haven't yet
+ * cleared during mac80211's suspend cycle.
+ */
+static bool ieee80211_can_queue_work(struct ieee80211_local *local)
+{
+        if (WARN(local->suspended, "queueing ieee80211 work while "
+		 "going to suspend\n"))
+                return false;
+
+	return true;
+}
+
+void ieee80211_queue_work(struct ieee80211_hw *hw, struct work_struct *work)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	if (!ieee80211_can_queue_work(local))
+		return;
+
+	queue_work(local->workqueue, work);
+}
+EXPORT_SYMBOL(ieee80211_queue_work);
+
+void ieee80211_queue_delayed_work(struct ieee80211_hw *hw,
+				  struct delayed_work *dwork,
+				  unsigned long delay)
+{
+	struct ieee80211_local *local = hw_to_local(hw);
+
+	if (!ieee80211_can_queue_work(local))
+		return;
+
+	queue_delayed_work(local->workqueue, dwork, delay);
+}
+EXPORT_SYMBOL(ieee80211_queue_delayed_work);
+
 void ieee802_11_parse_elems(u8 *start, size_t len,
 			    struct ieee802_11_elems *elems)
 {
@@ -1114,3 +1154,4 @@ int ieee80211_reconfig(struct ieee80211_local *local)
 #endif
 	return 0;
 }
+