mac80211: introduce plink lock for plink fields

The mesh plink code uses sta->lock to serialize access to the
plink state fields between the peer link state machine and the
peer link timer.  Some paths (e.g. those involving
mps_qos_null_tx()) unfortunately hold this spinlock across
frame tx, which is soon to be disallowed.  Add a new spinlock
just for plink access.
Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh_plink.c

@@ -72,10 +72,11 @@ static bool rssi_threshold_check(struct ieee80211_sub_if_data *sdata,
  *
  * @sta: mesh peer link to restart
  *
- * Locking: this function must be called holding sta->lock
+ * Locking: this function must be called holding sta->plink_lock
  */
 static inline void mesh_plink_fsm_restart(struct sta_info *sta)
 {
+	lockdep_assert_held(&sta->plink_lock);
 	sta->plink_state = NL80211_PLINK_LISTEN;
 	sta->llid = sta->plid = sta->reason = 0;
 	sta->plink_retries = 0;
@@ -213,13 +214,15 @@ static u32 mesh_set_ht_prot_mode(struct ieee80211_sub_if_data *sdata)
  * All mesh paths with this peer as next hop will be flushed
  * Returns beacon changed flag if the beacon content changed.
  *
- * Locking: the caller must hold sta->lock
+ * Locking: the caller must hold sta->plink_lock
  */
 static u32 __mesh_plink_deactivate(struct sta_info *sta)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	u32 changed = 0;
 
+	lockdep_assert_held(&sta->plink_lock);
+
 	if (sta->plink_state == NL80211_PLINK_ESTAB)
 		changed = mesh_plink_dec_estab_count(sdata);
 	sta->plink_state = NL80211_PLINK_BLOCKED;
@@ -244,13 +247,13 @@ u32 mesh_plink_deactivate(struct sta_info *sta)
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
 	u32 changed;
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 	changed = __mesh_plink_deactivate(sta);
 	sta->reason = WLAN_REASON_MESH_PEER_CANCELED;
 	mesh_plink_frame_tx(sdata, WLAN_SP_MESH_PEERING_CLOSE,
 			    sta->sta.addr, sta->llid, sta->plid,
 			    sta->reason);
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 
 	return changed;
 }
@@ -387,7 +390,7 @@ static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
 	sband = local->hw.wiphy->bands[band];
 	rates = ieee80211_sta_get_rates(sdata, elems, band, &basic_rates);
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 	sta->last_rx = jiffies;
 
 	/* rates and capabilities don't change during peering */
@@ -419,7 +422,7 @@ static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
 	else
 		rate_control_rate_update(local, sband, sta, changed);
 out:
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 }
 
 static struct sta_info *
@@ -552,7 +555,7 @@ static void mesh_plink_timer(unsigned long data)
 	if (sta->sdata->local->quiescing)
 		return;
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 
 	/* If a timer fires just before a state transition on another CPU,
 	 * we may have already extended the timeout and changed state by the
@@ -563,7 +566,7 @@ static void mesh_plink_timer(unsigned long data)
 		mpl_dbg(sta->sdata,
 			"Ignoring timer for %pM in state %s (timer adjusted)",
 			sta->sta.addr, mplstates[sta->plink_state]);
-		spin_unlock_bh(&sta->lock);
+		spin_unlock_bh(&sta->plink_lock);
 		return;
 	}
 
@@ -573,7 +576,7 @@ static void mesh_plink_timer(unsigned long data)
 		mpl_dbg(sta->sdata,
 			"Ignoring timer for %pM in state %s (timer deleted)",
 			sta->sta.addr, mplstates[sta->plink_state]);
-		spin_unlock_bh(&sta->lock);
+		spin_unlock_bh(&sta->plink_lock);
 		return;
 	}
 
@@ -619,7 +622,7 @@ static void mesh_plink_timer(unsigned long data)
 	default:
 		break;
 	}
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 	if (action)
 		mesh_plink_frame_tx(sdata, action, sta->sta.addr,
 				    sta->llid, sta->plid, reason);
@@ -674,16 +677,16 @@ u32 mesh_plink_open(struct sta_info *sta)
 	if (!test_sta_flag(sta, WLAN_STA_AUTH))
 		return 0;
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 	sta->llid = mesh_get_new_llid(sdata);
 	if (sta->plink_state != NL80211_PLINK_LISTEN &&
 	    sta->plink_state != NL80211_PLINK_BLOCKED) {
-		spin_unlock_bh(&sta->lock);
+		spin_unlock_bh(&sta->plink_lock);
 		return 0;
 	}
 	sta->plink_state = NL80211_PLINK_OPN_SNT;
 	mesh_plink_timer_set(sta, sdata->u.mesh.mshcfg.dot11MeshRetryTimeout);
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 	mpl_dbg(sdata,
 		"Mesh plink: starting establishment with %pM\n",
 		sta->sta.addr);
@@ -700,10 +703,10 @@ u32 mesh_plink_block(struct sta_info *sta)
 {
 	u32 changed;
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 	changed = __mesh_plink_deactivate(sta);
 	sta->plink_state = NL80211_PLINK_BLOCKED;
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 
 	return changed;
 }
@@ -758,7 +761,7 @@ static u32 mesh_plink_fsm(struct ieee80211_sub_if_data *sdata,
 	mpl_dbg(sdata, "peer %pM in state %s got event %s\n", sta->sta.addr,
 		mplstates[sta->plink_state], mplevents[event]);
 
-	spin_lock_bh(&sta->lock);
+	spin_lock_bh(&sta->plink_lock);
 	switch (sta->plink_state) {
 	case NL80211_PLINK_LISTEN:
 		switch (event) {
@@ -872,7 +875,7 @@ static u32 mesh_plink_fsm(struct ieee80211_sub_if_data *sdata,
 		 */
 		break;
 	}
-	spin_unlock_bh(&sta->lock);
+	spin_unlock_bh(&sta->plink_lock);
 	if (action) {
 		mesh_plink_frame_tx(sdata, action, sta->sta.addr,
 				    sta->llid, sta->plid, sta->reason);

net/mac80211/sta_info.c

@@ -295,6 +295,7 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata,
 	INIT_WORK(&sta->ampdu_mlme.work, ieee80211_ba_session_work);
 	mutex_init(&sta->ampdu_mlme.mtx);
 #ifdef CONFIG_MAC80211_MESH
+	spin_lock_init(&sta->plink_lock);
 	if (ieee80211_vif_is_mesh(&sdata->vif) &&
 	    !sdata->u.mesh.user_mpm)
 		init_timer(&sta->plink_timer);

net/mac80211/sta_info.h

@@ -299,6 +299,7 @@ struct sta_ampdu_mlme {
  * @tid_seq: per-TID sequence numbers for sending to this STA
  * @ampdu_mlme: A-MPDU state machine state
  * @timer_to_tid: identity mapping to ID timers
+ * @plink_lock: serialize access to plink fields
  * @llid: Local link ID
  * @plid: Peer link ID
  * @reason: Cancel reason on PLINK_HOLDING state
@@ -422,9 +423,10 @@ struct sta_info {
 
 #ifdef CONFIG_MAC80211_MESH
 	/*
-	 * Mesh peer link attributes
+	 * Mesh peer link attributes, protected by plink_lock.
 	 * TODO: move to a sub-structure that is referenced with pointer?
 	 */
+	spinlock_t plink_lock;
 	u16 llid;
 	u16 plid;
 	u16 reason;
@@ -432,6 +434,7 @@ struct sta_info {
 	enum nl80211_plink_state plink_state;
 	u32 plink_timeout;
 	struct timer_list plink_timer;
+
 	s64 t_offset;
 	s64 t_offset_setpoint;
 	/* mesh power save */