iwlwifi: mvm: replace RS mutex with a spin_lock

The solution with the worker still had a bug, as in order
to get sta, rcu_read_lock should be used and thus no mutex
can be used inside iwl_mvm_rs_rate_init.

Also, spin_lock is a simpler solution, no need to spawn a
dedicated worker.
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/rs.h

@@ -376,9 +376,6 @@ struct iwl_lq_sta {
 	/* tx power reduce for this sta */
 	int tpc_reduce;
 
-	/* avoid races of reinit and update table from rx_tx */
-	struct mutex mutex;
-
 	/* persistent fields - initialized only once - keep last! */
 	struct lq_sta_pers {
 #ifdef CONFIG_MAC80211_DEBUGFS
@@ -393,6 +390,7 @@ struct iwl_lq_sta {
 		s8 last_rssi;
 		struct rs_rate_stats tx_stats[RS_COLUMN_COUNT][IWL_RATE_COUNT];
 		struct iwl_mvm *drv;
+		spinlock_t lock; /* for races in reinit/update table */
 	} pers;
 };
 
@@ -443,8 +441,6 @@ struct iwl_mvm_sta;
 int iwl_mvm_tx_protection(struct iwl_mvm *mvm, struct iwl_mvm_sta *mvmsta,
 			  bool enable);
 
-void iwl_mvm_rs_init_wk(struct work_struct *wk);
-
 #ifdef CONFIG_IWLWIFI_DEBUGFS
 void iwl_mvm_reset_frame_stats(struct iwl_mvm *mvm);
 #endif

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -1685,9 +1685,7 @@ int iwl_mvm_add_sta(struct iwl_mvm *mvm,
 	if (iwl_mvm_has_tlc_offload(mvm))
 		iwl_mvm_rs_add_sta(mvm, mvm_sta);
 	else
-		mutex_init(&mvm_sta->lq_sta.rs_drv.mutex);
-
-	INIT_WORK(&mvm_sta->rs_init_wk, iwl_mvm_rs_init_wk);
+		spin_lock_init(&mvm_sta->lq_sta.rs_drv.pers.lock);
 
 	iwl_mvm_toggle_tx_ant(mvm, &mvm_sta->tx_ant);
 
@@ -1850,8 +1848,6 @@ int iwl_mvm_rm_sta(struct iwl_mvm *mvm,
 	if (ret)
 		return ret;
 
-	cancel_work_sync(&mvm_sta->rs_init_wk);
-
 	/* flush its queues here since we are freeing mvm_sta */
 	ret = iwl_mvm_flush_sta(mvm, mvm_sta, false, 0);
 	if (ret)

drivers/net/wireless/intel/iwlwifi/mvm/sta.h

@@ -432,7 +432,6 @@ struct iwl_mvm_sta {
 		struct iwl_lq_sta_rs_fw rs_fw;
 		struct iwl_lq_sta rs_drv;
 	} lq_sta;
-	struct work_struct rs_init_wk;
 	struct ieee80211_vif *vif;
 	struct iwl_mvm_key_pn __rcu *ptk_pn[4];
 	struct iwl_mvm_rxq_dup_data *dup_data;