mac80211: remove tasklet enable/disable

Due to the way the tasklets work in mac80211 there's
no need to ever disable them.

However, we need to clear the pending packets when
taking down the last interface because otherwise
the tx_pending_tasklet might be queued if the
driver mucks with the queues (which it shouldn't).

I've had a situation occasionally with ar9170 in
which ksoftirq was using 100% CPU time because
a disabled tasklet was scheduled, and I think that
was due to ar9170 receiving a packet while the
tasklet was disabled. That's strange and it really
should not do that for other reasons, but there's
no need to waste that much CPU time over it, it
should just warn instead.

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

1 files changed, 13 insertions, 1 deletions

diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index d231c9323ad1..020a94a31106 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -12,7 +12,11 @@ static inline int drv_tx(struct ieee80211_local *local, struct sk_buff *skb)
 
 static inline int drv_start(struct ieee80211_local *local)
 {
-        int ret = local->ops->start(&local->hw);
+        int ret;
+
+        local->started = true;
+        smp_mb();
+        ret = local->ops->start(&local->hw);
         trace_drv_start(local, ret);
         return ret;
 }
@@ -21,6 +25,14 @@ static inline void drv_stop(struct ieee80211_local *local)
 {
         local->ops->stop(&local->hw);
         trace_drv_stop(local);
+
+        /* sync away all work on the tasklet before clearing started */
+        tasklet_disable(&local->tasklet);
+        tasklet_enable(&local->tasklet);
+
+        barrier();
+
+        local->started = false;
 }
 
 static inline int drv_add_interface(struct ieee80211_local *local,