mac80211: proper STA info locking

As discussed earlier, we can unify locking in struct sta_info
and use just a single spinlock protecting all members of the
structure that need protection. Many don't, but one of the
especially bad ones is the 'flags' member that can currently
be clobbered when RX and TX is being processed on different
CPUs at the same time.

Because having four spinlocks for different, mostly exclusive
parts of a single structure is overkill, this patch also kills
the ampdu and mesh plink spinlocks and uses just a single one
for everything. Because none of the spinlocks are nested, this
is safe.

It remains to be seen whether or not we should make the sta
flags use atomic bit operations instead, for now though this
is a safe thing and using atomic operations instead will be
very simple using the new static inline functions this patch
introduces for accessing sta->flags.

Since spin_lock_bh() is used with this lock, there shouldn't
be any contention even if aggregation is enabled at around the
same time as both requires frame transmission/reception which
is in a bh context.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: Tomas Winkler <tomasw@gmail.com>
Cc: Ron Rindjunsky <ron.rindjunsky@intel.com>
Cc: Luis Carlos Cobo <luisca@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 11 insertions, 10 deletions

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 3a03d78..5f31a62 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -256,7 +256,7 @@ ieee80211_tx_h_check_assoc(struct ieee80211_tx_data *tx)
 	if (tx->flags & IEEE80211_TX_PS_BUFFERED)
 		return TX_CONTINUE;
 
-	sta_flags = tx->sta ? tx->sta->flags : 0;
+	sta_flags = tx->sta ? get_sta_flags(tx->sta) : 0;
 
 	if (likely(tx->flags & IEEE80211_TX_UNICAST)) {
 		if (unlikely(!(sta_flags & WLAN_STA_ASSOC) &&
@@ -391,6 +391,7 @@ static ieee80211_tx_result
 ieee80211_tx_h_unicast_ps_buf(struct ieee80211_tx_data *tx)
 {
 	struct sta_info *sta = tx->sta;
+	u32 staflags;
 	DECLARE_MAC_BUF(mac);
 
 	if (unlikely(!sta ||
@@ -398,8 +399,10 @@ ieee80211_tx_h_unicast_ps_buf(struct ieee80211_tx_data *tx)
 		      (tx->fc & IEEE80211_FCTL_STYPE) == IEEE80211_STYPE_PROBE_RESP)))
 		return TX_CONTINUE;
 
-	if (unlikely((sta->flags & WLAN_STA_PS) &&
-		     !(sta->flags & WLAN_STA_PSPOLL))) {
+	staflags = get_sta_flags(sta);
+
+	if (unlikely((staflags & WLAN_STA_PS) &&
+		     !(staflags & WLAN_STA_PSPOLL))) {
 		struct ieee80211_tx_packet_data *pkt_data;
 #ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
 		printk(KERN_DEBUG "STA %s aid %d: PS buffer (entries "
@@ -430,13 +433,13 @@ ieee80211_tx_h_unicast_ps_buf(struct ieee80211_tx_data *tx)
 		return TX_QUEUED;
 	}
 #ifdef CONFIG_MAC80211_VERBOSE_PS_DEBUG
-	else if (unlikely(sta->flags & WLAN_STA_PS)) {
+	else if (unlikely(test_sta_flags(sta, WLAN_STA_PS))) {
 		printk(KERN_DEBUG "%s: STA %s in PS mode, but pspoll "
 		       "set -> send frame\n", tx->dev->name,
 		       print_mac(mac, sta->addr));
 	}
 #endif /* CONFIG_MAC80211_VERBOSE_PS_DEBUG */
-	sta->flags &= ~WLAN_STA_PSPOLL;
+	clear_sta_flags(sta, WLAN_STA_PSPOLL);
 
 	return TX_CONTINUE;
 }
@@ -697,7 +700,7 @@ ieee80211_tx_h_misc(struct ieee80211_tx_data *tx)
 	if (((fc & IEEE80211_FCTL_FTYPE) == IEEE80211_FTYPE_DATA) &&
 	    (tx->rate->flags & IEEE80211_RATE_SHORT_PREAMBLE) &&
 	    tx->sdata->bss_conf.use_short_preamble &&
-	    (!tx->sta || (tx->sta->flags & WLAN_STA_SHORT_PREAMBLE))) {
+	    (!tx->sta || test_sta_flags(tx->sta, WLAN_STA_SHORT_PREAMBLE))) {
 		tx->control->flags |= IEEE80211_TXCTL_SHORT_PREAMBLE;
 	}
 
@@ -1025,10 +1028,8 @@ __ieee80211_tx_prepare(struct ieee80211_tx_data *tx,
 
 	if (!tx->sta)
 		control->flags |= IEEE80211_TXCTL_CLEAR_PS_FILT;
-	else if (tx->sta->flags & WLAN_STA_CLEAR_PS_FILT) {
+	else if (test_and_clear_sta_flags(tx->sta, WLAN_STA_CLEAR_PS_FILT))
 		control->flags |= IEEE80211_TXCTL_CLEAR_PS_FILT;
-		tx->sta->flags &= ~WLAN_STA_CLEAR_PS_FILT;
-	}
 
 	hdrlen = ieee80211_get_hdrlen(tx->fc);
 	if (skb->len > hdrlen + sizeof(rfc1042_header) + 2) {
@@ -1486,7 +1487,7 @@ int ieee80211_subif_start_xmit(struct sk_buff *skb,
 		rcu_read_lock();
 		sta = sta_info_get(local, hdr.addr1);
 		if (sta)
-			sta_flags = sta->flags;
+			sta_flags = get_sta_flags(sta);
 		rcu_read_unlock();
 	}