rtlwifi: Fix scheduling while atomic bug

Kernel commits 41affd52 and 6539306b changed the locking in rtl_lps_leave()
from a spinlock to a mutex by doing the calls indirectly from a work queue
to reduce the time that interrupts were disabled. This change was fine for
most systems; however a scheduling while atomic bug was reported in
https://bugzilla.redhat.com/show_bug.cgi?id=903881. The backtrace indicates
that routine rtl_is_special(), which calls rtl_lps_leave() in three places
was entered in atomic context. These direct calls are replaced by putting a
request on the appropriate work queue.
Signed-off-by: NLarry Finger <Larry.Finger@lwfinger.net>
Reported-and-tested-by: NNathaniel Doherty <ntdoherty@gmail.com>
Cc: Nathaniel Doherty <ntdoherty@gmail.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rtlwifi/base.c

@@ -1004,7 +1004,8 @@ u8 rtl_is_special_data(struct ieee80211_hw *hw, struct sk_buff *skb, u8 is_tx)
 					 is_tx ? "Tx" : "Rx");
 
 				if (is_tx) {
-					rtl_lps_leave(hw);
+					schedule_work(&rtlpriv->
+						      works.lps_leave_work);
 					ppsc->last_delaylps_stamp_jiffies =
 					    jiffies;
 				}
@@ -1014,7 +1015,7 @@ u8 rtl_is_special_data(struct ieee80211_hw *hw, struct sk_buff *skb, u8 is_tx)
 		}
 	} else if (ETH_P_ARP == ether_type) {
 		if (is_tx) {
-			rtl_lps_leave(hw);
+			schedule_work(&rtlpriv->works.lps_leave_work);
 			ppsc->last_delaylps_stamp_jiffies = jiffies;
 		}
 
@@ -1024,7 +1025,7 @@ u8 rtl_is_special_data(struct ieee80211_hw *hw, struct sk_buff *skb, u8 is_tx)
 			 "802.1X %s EAPOL pkt!!\n", is_tx ? "Tx" : "Rx");
 
 		if (is_tx) {
-			rtl_lps_leave(hw);
+			schedule_work(&rtlpriv->works.lps_leave_work);
 			ppsc->last_delaylps_stamp_jiffies = jiffies;
 		}