ath9k: fix race with IEEE80211_CONF_PS checks

There is a small window where the mac80211 changes the IEEE80211_CONF_PS
flag, and then informs the driver about the change. We have a race
condition if we are checking the flag in the same time. Avoid it by
introducing a local variable, and using that instead of checking the
IEEE80211_CONF_PS flag directly.

This fix the problem reported by Luis:
http://article.gmane.org/gmane.linux.kernel.wireless.general/34363

Changes-licensed-under: ISC
Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

4 files changed, 12 insertions, 15 deletions

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index e2ebf1a56c0..3a978bfa246 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -573,6 +573,7 @@ struct ath_softc {
         u32 keymax;
         DECLARE_BITMAP(keymap, ATH_KEYMAX);
         u8 splitmic;
+        bool ps_enabled;
         unsigned long ps_usecount;
         enum ath9k_int imask;
         enum ath9k_ht_extprotspacing ht_extprotspacing;
diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index da3226994de..e6e52f48e71 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -2863,10 +2863,8 @@ void ath9k_ps_wakeup(struct ath_softc *sc)
         if (++sc->ps_usecount != 1)
                 goto unlock;
 
-        if (sc->sc_ah->power_mode != ATH9K_PM_AWAKE) {
-                sc->sc_ah->restore_mode = sc->sc_ah->power_mode;
+        if (sc->sc_ah->power_mode != ATH9K_PM_AWAKE)
                 ath9k_hw_setpower_nolock(sc->sc_ah, ATH9K_PM_AWAKE);
-        }
 
  unlock:
         spin_unlock_irqrestore(&sc->sc_pm_lock, flags);
@@ -2880,13 +2878,12 @@ void ath9k_ps_restore(struct ath_softc *sc)
         if (--sc->ps_usecount != 0)
                 goto unlock;
 
-        if ((sc->hw->conf.flags & IEEE80211_CONF_PS) &&
-                !(sc->sc_flags & (SC_OP_WAIT_FOR_BEACON |
-                                SC_OP_WAIT_FOR_CAB |
-                                SC_OP_WAIT_FOR_PSPOLL_DATA |
-                                SC_OP_WAIT_FOR_TX_ACK)))
-                ath9k_hw_setpower_nolock(sc->sc_ah,
-                                      sc->sc_ah->restore_mode);
+        if (sc->ps_enabled &&
+            !(sc->sc_flags & (SC_OP_WAIT_FOR_BEACON |
+                              SC_OP_WAIT_FOR_CAB |
+                              SC_OP_WAIT_FOR_PSPOLL_DATA |
+                              SC_OP_WAIT_FOR_TX_ACK)))
+                ath9k_hw_setpower_nolock(sc->sc_ah, ATH9K_PM_NETWORK_SLEEP);
 
  unlock:
         spin_unlock_irqrestore(&sc->sc_pm_lock, flags);
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index 37f7d3defb8..2e196df1089 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -421,7 +421,6 @@ struct ath_hw {
 
         enum nl80211_iftype opmode;
         enum ath9k_power_mode power_mode;
-        enum ath9k_power_mode restore_mode;
 
         struct ath9k_nfcal_hist nfCalHist[NUM_NF_READINGS];
         struct ar5416Stats stats;
diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 1c648db1092..87f99718393 100644
--- a/drivers/net/wireless/ath/ath9k/main.c
+++ b/drivers/net/wireless/ath/ath9k/main.c
@@ -499,8 +499,7 @@ static void ath9k_tasklet(unsigned long data)
         if (status & ATH9K_INT_TX)
                 ath_tx_tasklet(sc);
 
-        if ((status & ATH9K_INT_TSFOOR) &&
-            (sc->hw->conf.flags & IEEE80211_CONF_PS)) {
+        if ((status & ATH9K_INT_TSFOOR) && sc->ps_enabled) {
                 /*
                  * TSF sync does not look correct; remain awake to sync with
                  * the next Beacon.
@@ -2001,7 +2000,7 @@ static int ath9k_tx(struct ieee80211_hw *hw,
                 goto exit;
         }
 
-        if (sc->hw->conf.flags & IEEE80211_CONF_PS) {
+        if (sc->ps_enabled) {
                 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
                 /*
                  * mac80211 does not set PM field for normal data frames, so we
@@ -2289,8 +2288,9 @@ static int ath9k_config(struct ieee80211_hw *hw, u32 changed)
                                 }
                                 ath9k_hw_setrxabort(sc->sc_ah, 1);
                         }
-                        ath9k_hw_setpower(sc->sc_ah, ATH9K_PM_NETWORK_SLEEP);
+                        sc->ps_enabled = true;
                 } else {
+                        sc->ps_enabled = false;
                         ath9k_hw_setpower(sc->sc_ah, ATH9K_PM_AWAKE);
                         if (!(ah->caps.hw_caps &
                               ATH9K_HW_CAP_AUTOSLEEP)) {