qcacld-3.0: Fix to avoid acquiring mutex in atomic context

Propagation from qcacld-2.0 to qcacld-3.0

When a radar is indicated from WMA to HDD,  it happens in a soft
irq context and the dfs_radar_found flag is set by acquiring
a mutex which leads to apps crash.  The crash happens if the mutex for
dfs_radar_found flag is being held by the main thread and as a result
the soft irq thread seeking the same mutex will be put in the kernel
sleep queue leading to apps crash as sleeping is not allowed in soft irq
context.

Fix the issue by using spinlock instead of mutexes.  An exception
has been made to use the spinlock in the main thread context to
work around the complications involving for radar indication
callback to happen in worker thread context instead of soft
irq context.

Change-Id: I4bc01ac8991c593ffcaf6ee532f4594cb8beba16
CRs-Fixed: 928394

core/hdd/inc/wlan_hdd_main.h

@@ -1420,7 +1420,7 @@ struct hdd_context_s {
 	 * radar found indication and application triggered channel
 	 * switch.
 	 */
-	struct mutex dfs_lock;
+	qdf_spinlock_t dfs_lock;
 	/*
 	 * place to store FTM capab of target. This allows changing of FTM capab
 	 * at runtime and intersecting it with target capab before updating.

core/hdd/src/wlan_hdd_hostapd.c

@@ -116,7 +116,7 @@ int hdd_sap_context_init(hdd_context_t *hdd_ctx)
 	qdf_wake_lock_create(&hdd_ctx->sap_wake_lock, "qcom_sap_wakelock");
 	qdf_spinlock_create(&hdd_ctx->sap_update_info_lock);
 
-	mutex_init(&hdd_ctx->dfs_lock);
+	qdf_spinlock_create(&hdd_ctx->dfs_lock);
 
 	return 0;
 }
@@ -217,7 +217,7 @@ void hdd_sap_context_destroy(hdd_context_t *hdd_ctx)
 	mutex_destroy(&hdd_ctx->sap_lock);
 	qdf_wake_lock_destroy(&hdd_ctx->sap_wake_lock);
 
-	mutex_destroy(&hdd_ctx->dfs_lock);
+	qdf_spinlock_destroy(&hdd_ctx->dfs_lock);
 
 	qdf_spinlock_destroy(&hdd_ctx->sap_update_info_lock);
 
@@ -991,9 +991,9 @@ QDF_STATUS hdd_hostapd_sap_event_cb(tpSap_Event pSapEvent,
 			}
 		}
 
-		mutex_lock(&pHddCtx->dfs_lock);
+		qdf_spin_lock_bh(&pHddCtx->dfs_lock);
 		pHddCtx->dfs_radar_found = false;
-		mutex_unlock(&pHddCtx->dfs_lock);
+		qdf_spin_unlock_bh(&pHddCtx->dfs_lock);
 
 		wlansap_get_dfs_ignore_cac(pHddCtx->hHal, &ignoreCAC);
 
@@ -1111,9 +1111,9 @@ QDF_STATUS hdd_hostapd_sap_event_cb(tpSap_Event pSapEvent,
 			hdd_info("Sent CAC start to user space");
 		}
 
-		mutex_lock(&pHddCtx->dfs_lock);
+		qdf_spin_lock_bh(&pHddCtx->dfs_lock);
 		pHddCtx->dfs_radar_found = false;
-		mutex_unlock(&pHddCtx->dfs_lock);
+		qdf_spin_unlock_bh(&pHddCtx->dfs_lock);
 		break;
 	case eSAP_DFS_CAC_INTERRUPTED:
 		/*
@@ -1999,9 +1999,9 @@ int hdd_softap_set_channel_change(struct net_device *dev, int target_channel,
 		}
 	}
 
-	mutex_lock(&pHddCtx->dfs_lock);
+	qdf_spin_lock_bh(&pHddCtx->dfs_lock);
 	if (pHddCtx->dfs_radar_found == true) {
-		mutex_unlock(&pHddCtx->dfs_lock);
+		qdf_spin_unlock_bh(&pHddCtx->dfs_lock);
 		hddLog(LOGE, FL("Channel switch in progress!!"));
 		return -EBUSY;
 	}
@@ -2015,7 +2015,7 @@ int hdd_softap_set_channel_change(struct net_device *dev, int target_channel,
 	 * post eSAP_START_BSS_EVENT success event to HDD.
 	 */
 	pHddCtx->dfs_radar_found = true;
-	mutex_unlock(&pHddCtx->dfs_lock);
+	qdf_spin_unlock_bh(&pHddCtx->dfs_lock);
 	/*
 	 * Post the Channel Change request to SAP.
 	 */
@@ -2039,9 +2039,9 @@ int hdd_softap_set_channel_change(struct net_device *dev, int target_channel,
 		 * radar found flag and also restart the netif
 		 * queues.
 		 */
-		mutex_lock(&pHddCtx->dfs_lock);
+		qdf_spin_lock_bh(&pHddCtx->dfs_lock);
 		pHddCtx->dfs_radar_found = false;
-		mutex_unlock(&pHddCtx->dfs_lock);
+		qdf_spin_unlock_bh(&pHddCtx->dfs_lock);
 
 		ret = -EINVAL;
 	}

core/hdd/src/wlan_hdd_main.c

@@ -1402,9 +1402,9 @@ void hdd_update_tgt_cfg(void *context, void *param)
  * @context:	HDD context pointer
  * @param:	HDD radar indication pointer
  *
- * This function is invoked when a radar in found on the
- * SAP current operating channel and Data Tx from netif
- * has to be stopped to honor the DFS regulations.
+ * This function is invoked in atomic context when a radar
+ * is found on the SAP current operating channel and Data Tx
+ * from netif has to be stopped to honor the DFS regulations.
  * Actions: Stop the netif Tx queues,Indicate Radar present
  * in HDD context for future usage.
  *
@@ -1424,18 +1424,18 @@ bool hdd_dfs_indicate_radar(void *context, void *param)
 		return true;
 
 	if (true == hdd_radar_event->dfs_radar_status) {
-		mutex_lock(&hdd_ctx->dfs_lock);
+		qdf_spin_lock_bh(&hdd_ctx->dfs_lock);
 		if (hdd_ctx->dfs_radar_found) {
 			/*
 			 * Application already triggered channel switch
 			 * on current channel, so return here.
 			 */
-			mutex_unlock(&hdd_ctx->dfs_lock);
+			qdf_spin_unlock_bh(&hdd_ctx->dfs_lock);
 			return false;
 		}
 
 		hdd_ctx->dfs_radar_found = true;
-		mutex_unlock(&hdd_ctx->dfs_lock);
+		qdf_spin_unlock_bh(&hdd_ctx->dfs_lock);
 
 		status = hdd_get_front_adapter(hdd_ctx, &adapterNode);
 		while (NULL != adapterNode && QDF_STATUS_SUCCESS == status) {