iwlagn: fix channel switch locking

We use priv->mutex to avoid race conditions between iwl_chswitch_done()
and iwlagn_mac_channel_switch(), when marking channel switch in
progress. But iwl_chswitch_done() can be called in atomic context
from iwl_rx_csa() or with mutex already taken from iwlagn_commit_rxon().

These bugs were introduced by:

commit 79d07325
Author: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Date:   Thu May 6 08:54:11 2010 -0700

    iwlwifi: support channel switch offload in driver

To fix remove mutex from iwl_chswitch_done() and use atomic bitops for
marking channel switch pending.

Also remove iwl2030_hw_channel_switch() since 2000 series adapters are
2.4GHz only devices.

Cc: stable@kernel.org # 2.6.36+
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-2000.c

@@ -177,79 +177,6 @@ static int iwl2000_hw_set_hw_params(struct iwl_priv *priv)
 	return 0;
 }
 
-static int iwl2030_hw_channel_switch(struct iwl_priv *priv,
-                                    struct ieee80211_channel_switch *ch_switch)
-{
-	/*
-	 * MULTI-FIXME
-	 * See iwl_mac_channel_switch.
-	 */
-	struct iwl_rxon_context *ctx = &priv->contexts[IWL_RXON_CTX_BSS];
-	struct iwl6000_channel_switch_cmd cmd;
-	const struct iwl_channel_info *ch_info;
-	u32 switch_time_in_usec, ucode_switch_time;
-	u16 ch;
-	u32 tsf_low;
-	u8 switch_count;
-	u16 beacon_interval = le16_to_cpu(ctx->timing.beacon_interval);
-	struct ieee80211_vif *vif = ctx->vif;
-	struct iwl_host_cmd hcmd = {
-		.id = REPLY_CHANNEL_SWITCH,
-		.len = { sizeof(cmd), },
-		.flags = CMD_SYNC,
-		.data = { &cmd, },
-	};
-
-	cmd.band = priv->band == IEEE80211_BAND_2GHZ;
-	ch = ch_switch->channel->hw_value;
-	IWL_DEBUG_11H(priv, "channel switch from %u to %u\n",
-		ctx->active.channel, ch);
-	cmd.channel = cpu_to_le16(ch);
-	cmd.rxon_flags = ctx->staging.flags;
-	cmd.rxon_filter_flags = ctx->staging.filter_flags;
-	switch_count = ch_switch->count;
-	tsf_low = ch_switch->timestamp & 0x0ffffffff;
-	/*
-	 * calculate the ucode channel switch time
-	 * adding TSF as one of the factor for when to switch
-	 */
-	if ((priv->ucode_beacon_time > tsf_low) && beacon_interval) {
-		if (switch_count > ((priv->ucode_beacon_time - tsf_low) /
-		    beacon_interval)) {
-			switch_count -= (priv->ucode_beacon_time -
-				tsf_low) / beacon_interval;
-		} else
-			switch_count = 0;
-	}
-	if (switch_count <= 1)
-		cmd.switch_time = cpu_to_le32(priv->ucode_beacon_time);
-	else {
-		switch_time_in_usec =
-			vif->bss_conf.beacon_int * switch_count * TIME_UNIT;
-		ucode_switch_time = iwl_usecs_to_beacons(priv,
-						switch_time_in_usec,
-						beacon_interval);
-		cmd.switch_time = iwl_add_beacon_time(priv,
-						priv->ucode_beacon_time,
-						ucode_switch_time,
-						beacon_interval);
-	}
-	IWL_DEBUG_11H(priv, "uCode time for the switch is 0x%x\n",
-		      cmd.switch_time);
-	ch_info = iwl_get_channel_info(priv, priv->band, ch);
-	if (ch_info)
-		cmd.expect_beacon = is_channel_radar(ch_info);
-	else {
-		IWL_ERR(priv, "invalid channel switch from %u to %u\n",
-			ctx->active.channel, ch);
-		return -EFAULT;
-	}
-	priv->switch_rxon.channel = cmd.channel;
-	priv->switch_rxon.switch_in_progress = true;
-
-	return iwl_send_cmd_sync(priv, &hcmd);
-}
-
 static struct iwl_lib_ops iwl2000_lib = {
 	.set_hw_params = iwl2000_hw_set_hw_params,
 	.rx_handler_setup = iwlagn_rx_handler_setup,
@@ -258,7 +185,6 @@ static struct iwl_lib_ops iwl2000_lib = {
 	.is_valid_rtc_data_addr = iwlagn_hw_valid_rtc_data_addr,
 	.send_tx_power = iwlagn_send_tx_power,
 	.update_chain_flags = iwl_update_chain_flags,
-	.set_channel_switch = iwl2030_hw_channel_switch,
 	.apm_ops = {
 		.init = iwl_apm_init,
 		.config = iwl2000_nic_config,

drivers/net/wireless/iwlwifi/iwl-5000.c

@@ -331,8 +331,6 @@ static int iwl5000_hw_channel_switch(struct iwl_priv *priv,
 			ctx->active.channel, ch);
 		return -EFAULT;
 	}
-	priv->switch_rxon.channel = cmd.channel;
-	priv->switch_rxon.switch_in_progress = true;
 
 	return iwl_send_cmd_sync(priv, &hcmd);
 }

drivers/net/wireless/iwlwifi/iwl-6000.c

@@ -270,8 +270,6 @@ static int iwl6000_hw_channel_switch(struct iwl_priv *priv,
 			ctx->active.channel, ch);
 		return -EFAULT;
 	}
-	priv->switch_rxon.channel = cmd.channel;
-	priv->switch_rxon.switch_in_progress = true;
 
 	return iwl_send_cmd_sync(priv, &hcmd);
 }

drivers/net/wireless/iwlwifi/iwl-agn-rxon.c

@@ -342,10 +342,10 @@ int iwlagn_commit_rxon(struct iwl_priv *priv, struct iwl_rxon_context *ctx)
 	 * receive commit_rxon request
 	 * abort any previous channel switch if still in process
 	 */
-	if (priv->switch_rxon.switch_in_progress &&
-	    (priv->switch_rxon.channel != ctx->staging.channel)) {
+	if (test_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status) &&
+	    (priv->switch_channel != ctx->staging.channel)) {
 		IWL_DEBUG_11H(priv, "abort channel switch on %d\n",
-		      le16_to_cpu(priv->switch_rxon.channel));
+			      le16_to_cpu(priv->switch_channel));
 		iwl_chswitch_done(priv, false);
 	}
 

drivers/net/wireless/iwlwifi/iwl-agn.c

@@ -2843,16 +2843,13 @@ static void iwlagn_mac_channel_switch(struct ieee80211_hw *hw,
 		goto out;
 
 	if (test_bit(STATUS_EXIT_PENDING, &priv->status) ||
-	    test_bit(STATUS_SCANNING, &priv->status))
+	    test_bit(STATUS_SCANNING, &priv->status) ||
+	    test_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status))
 		goto out;
 
 	if (!iwl_is_associated_ctx(ctx))
 		goto out;
 
-	/* channel switch in progress */
-	if (priv->switch_rxon.switch_in_progress == true)
-		goto out;
-
 	if (priv->cfg->ops->lib->set_channel_switch) {
 
 		ch = channel->hw_value;
@@ -2901,15 +2898,19 @@ static void iwlagn_mac_channel_switch(struct ieee80211_hw *hw,
 			 * at this point, staging_rxon has the
 			 * configuration for channel switch
 			 */
+			set_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status);
+			priv->switch_channel = cpu_to_le16(ch);
 			if (priv->cfg->ops->lib->set_channel_switch(priv,
-								    ch_switch))
-				priv->switch_rxon.switch_in_progress = false;
+								    ch_switch)) {
+				clear_bit(STATUS_CHANNEL_SWITCH_PENDING,
+					  &priv->status);
+				priv->switch_channel = 0;
+				ieee80211_chswitch_done(ctx->vif, false);
+			}
 		}
 	}
 out:
 	mutex_unlock(&priv->mutex);
-	if (!priv->switch_rxon.switch_in_progress)
-		ieee80211_chswitch_done(ctx->vif, false);
 	IWL_DEBUG_MAC80211(priv, "leave\n");
 }
 

drivers/net/wireless/iwlwifi/iwl-core.c

@@ -843,12 +843,8 @@ void iwl_chswitch_done(struct iwl_priv *priv, bool is_success)
 	if (test_bit(STATUS_EXIT_PENDING, &priv->status))
 		return;
 
-	if (priv->switch_rxon.switch_in_progress) {
+	if (test_and_clear_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status))
 		ieee80211_chswitch_done(ctx->vif, is_success);
-		mutex_lock(&priv->mutex);
-		priv->switch_rxon.switch_in_progress = false;
-		mutex_unlock(&priv->mutex);
-	}
 }
 
 #ifdef CONFIG_IWLWIFI_DEBUG

drivers/net/wireless/iwlwifi/iwl-core.h

@@ -560,6 +560,7 @@ void iwlcore_free_geos(struct iwl_priv *priv);
 #define STATUS_POWER_PMI	16
 #define STATUS_FW_ERROR		17
 #define STATUS_DEVICE_ENABLED	18
+#define STATUS_CHANNEL_SWITCH_PENDING 19
 
 
 static inline int iwl_is_ready(struct iwl_priv *priv)

drivers/net/wireless/iwlwifi/iwl-dev.h

@@ -981,17 +981,6 @@ struct traffic_stats {
 #endif
 };
 
-/*
- * iwl_switch_rxon: "channel switch" structure
- *
- * @ switch_in_progress: channel switch in progress
- * @ channel: new channel
- */
-struct iwl_switch_rxon {
-	bool switch_in_progress;
-	__le16 channel;
-};
-
 /*
  * schedule the timer to wake up every UCODE_TRACE_PERIOD milliseconds
  * to perform continuous uCode event logging operation if enabled
@@ -1287,7 +1276,7 @@ struct iwl_priv {
 
 	struct iwl_rxon_context contexts[NUM_IWL_RXON_CTX];
 
-	struct iwl_switch_rxon switch_rxon;
+	__le16 switch_channel;
 
 	struct {
 		u32 error_event_table;

drivers/net/wireless/iwlwifi/iwl-rx.c

@@ -250,9 +250,10 @@ static void iwl_rx_csa(struct iwl_priv *priv, struct iwl_rx_mem_buffer *rxb)
 	struct iwl_rxon_context *ctx = &priv->contexts[IWL_RXON_CTX_BSS];
 	struct iwl_rxon_cmd *rxon = (void *)&ctx->active;
 
-	if (priv->switch_rxon.switch_in_progress) {
-		if (!le32_to_cpu(csa->status) &&
-		    (csa->channel == priv->switch_rxon.channel)) {
+	if (!test_bit(STATUS_CHANNEL_SWITCH_PENDING, &priv->status))
+		return;
+
+	if (!le32_to_cpu(csa->status) && csa->channel == priv->switch_channel) {
 		rxon->channel = csa->channel;
 		ctx->staging.channel = csa->channel;
 		IWL_DEBUG_11H(priv, "CSA notif: channel %d\n",
@@ -263,7 +264,6 @@ static void iwl_rx_csa(struct iwl_priv *priv, struct iwl_rx_mem_buffer *rxb)
 			le16_to_cpu(csa->channel));
 		iwl_chswitch_done(priv, false);
 	}
-	}
 }