iwlegacy: fix channel switch locking

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

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

Cc: stable@kernel.org # 2.6.39+
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

5 files changed, 28 insertions, 46 deletions

diff --git a/drivers/net/wireless/iwlegacy/iwl-4965.c b/drivers/net/wireless/iwlegacy/iwl-4965.c
index e1b89220c18..facc94e74b0 100644
--- a/drivers/net/wireless/iwlegacy/iwl-4965.c
+++ b/drivers/net/wireless/iwlegacy/iwl-4965.c
@@ -1218,10 +1218,10 @@ static int iwl4965_commit_rxon(struct iwl_priv *priv, struct iwl_rxon_context *c
          * 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_legacy_chswitch_done(priv, false);
         }
 
@@ -1404,9 +1404,6 @@ static int iwl4965_hw_channel_switch(struct iwl_priv *priv,
                 return rc;
         }
 
-        priv->switch_rxon.channel = cmd.channel;
-        priv->switch_rxon.switch_in_progress = true;
-
         return iwl_legacy_send_cmd_pdu(priv,
                          REPLY_CHANNEL_SWITCH, sizeof(cmd), &cmd);
 }
diff --git a/drivers/net/wireless/iwlegacy/iwl-core.c b/drivers/net/wireless/iwlegacy/iwl-core.c
index 42df8321dae..3be76bd5499 100644
--- a/drivers/net/wireless/iwlegacy/iwl-core.c
+++ b/drivers/net/wireless/iwlegacy/iwl-core.c
@@ -859,12 +859,8 @@ void iwl_legacy_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);
-        }
 }
 EXPORT_SYMBOL(iwl_legacy_chswitch_done);
 
@@ -876,19 +872,19 @@ void iwl_legacy_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_legacy_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)) {
-                        rxon->channel = csa->channel;
-                        ctx->staging.channel = csa->channel;
-                        IWL_DEBUG_11H(priv, "CSA notif: channel %d\n",
-                              le16_to_cpu(csa->channel));
-                        iwl_legacy_chswitch_done(priv, true);
-                } else {
-                        IWL_ERR(priv, "CSA notif (fail) : channel %d\n",
+        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",
                               le16_to_cpu(csa->channel));
-                        iwl_legacy_chswitch_done(priv, false);
-                }
+                iwl_legacy_chswitch_done(priv, true);
+        } else {
+                IWL_ERR(priv, "CSA notif (fail) : channel %d\n",
+                        le16_to_cpu(csa->channel));
+                iwl_legacy_chswitch_done(priv, false);
         }
 }
 EXPORT_SYMBOL(iwl_legacy_rx_csa);
diff --git a/drivers/net/wireless/iwlegacy/iwl-core.h b/drivers/net/wireless/iwlegacy/iwl-core.h
index bc66c604106..c5fbda0760d 100644
--- a/drivers/net/wireless/iwlegacy/iwl-core.h
+++ b/drivers/net/wireless/iwlegacy/iwl-core.h
@@ -560,7 +560,7 @@ void iwl_legacy_free_geos(struct iwl_priv *priv);
 #define STATUS_SCAN_HW          15
 #define STATUS_POWER_PMI        16
 #define STATUS_FW_ERROR         17
-
+#define STATUS_CHANNEL_SWITCH_PENDING 18
 
 static inline int iwl_legacy_is_ready(struct iwl_priv *priv)
 {
diff --git a/drivers/net/wireless/iwlegacy/iwl-dev.h b/drivers/net/wireless/iwlegacy/iwl-dev.h
index be0106c6a2d..ea30122669e 100644
--- a/drivers/net/wireless/iwlegacy/iwl-dev.h
+++ b/drivers/net/wireless/iwlegacy/iwl-dev.h
@@ -855,17 +855,6 @@ struct traffic_stats {
 };
 
 /*
- * 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
  */
@@ -1115,7 +1104,7 @@ struct iwl_priv {
 
         struct iwl_rxon_context contexts[NUM_IWL_RXON_CTX];
 
-        struct iwl_switch_rxon switch_rxon;
+        __le16 switch_channel;
 
         /* 1st responses from initialize and runtime uCode images.
          * _4965's initialize alive response contains some calibration data. */
diff --git a/drivers/net/wireless/iwlegacy/iwl4965-base.c b/drivers/net/wireless/iwlegacy/iwl4965-base.c
index af2ae22fcfd..7157ba52968 100644
--- a/drivers/net/wireless/iwlegacy/iwl4965-base.c
+++ b/drivers/net/wireless/iwlegacy/iwl4965-base.c
@@ -2861,16 +2861,13 @@ void iwl4965_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_legacy_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;
@@ -2919,15 +2916,18 @@ void iwl4965_mac_channel_switch(struct ieee80211_hw *hw,
                          * at this point, staging_rxon has the
                          * configuration for channel switch
                          */
-                        if (priv->cfg->ops->lib->set_channel_switch(priv,
-                                                                    ch_switch))
-                                priv->switch_rxon.switch_in_progress = false;
+                        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)) {
+                                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");
 }