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>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/wireless/ath/ath9k/main.c b/drivers/net/wireless/ath/ath9k/main.c
index 1c648db10920..87f997183936 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)) {