mac80211: fix station entry leak/warning while suspending

commit b20d34c458bc2bbd0a4624f2933581e01e72d875 upstream.

Since Stanislaw's patches, when suspending while connected,
cfg80211 will disconnect. This causes the AP station to be
removed, which uses call_rcu() to clean up. Due to needing
process context, this queues a work struct on the mac80211
workqueue. This will warn and fail when already suspended,
which can happen if the rcu call doesn't happen quickly.

To fix this, replace the synchronize_net() which is really
just synchronize_rcu_expedited() with rcu_barrier(), which
unlike synchronize_rcu() waits until RCU callback have run
and thus avoids this issue.

In theory, this can even happen without Stanislaw's change
to disconnect on suspend since userspace might disconnect
just before suspending, though then it's unlikely that the
call_rcu() will be delayed long enough.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/mac80211/pm.c b/net/mac80211/pm.c
index 79a48f37d4092b27a88b8fa136f15a51812365f2..64619f418fd8c881eebee0a5059bce6065f1e01b 100644 (file)
--- a/net/mac80211/pm.c
+++ b/net/mac80211/pm.c
@@ -52,8 +52,8 @@ int __ieee80211_suspend(struct ieee80211_hw *hw, struct cfg80211_wowlan *wowlan)
        ieee80211_stop_queues_by_reason(hw,
                        IEEE80211_QUEUE_STOP_REASON_SUSPEND);
 
-       /* flush out all packets */
-       synchronize_net();
+       /* flush out all packets and station cleanup call_rcu()s */
+       rcu_barrier();
 
        drv_flush(local, false);