mac80211: Fix incorrect num_sta_ps decrement in ap_sta_ps_end

If the driver blocked this specific STA with the help of
ieee80211_sta_block_awake we won't clear WLAN_STA_PS_STA later but
still decrement num_sta_ps. Hence, the next data frame from this
STA will trigger ap_sta_ps_end again and also decrement num_sta_ps
again leading to an incorrect num_sta_ps counter.

This can result in problems with powersaving clients not waking up
from PS because the TIM calculation might be skipped due to the
incorrect num_sta_ps counter.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c
index 0c79593b1bbf..1fb4770a7d13 100644
--- a/net/mac80211/sta_info.c
+++ b/net/mac80211/sta_info.c
@@ -997,9 +997,11 @@ EXPORT_SYMBOL(ieee80211_find_sta);
 static void clear_sta_ps_flags(void *_sta)
 {
         struct sta_info *sta = _sta;
+        struct ieee80211_sub_if_data *sdata = sta->sdata;
 
         clear_sta_flag(sta, WLAN_STA_PS_DRIVER);
-        clear_sta_flag(sta, WLAN_STA_PS_STA);
+        if (test_and_clear_sta_flag(sta, WLAN_STA_PS_STA))
+                atomic_dec(&sdata->bss->num_sta_ps);
 }
 
 /* powersave support code */