qcacld-3.0: Fix RX data, peer unmap race condition

During peer unmap handler, while the peer is being deleted, there is a
possible race condition if the OL Rx thread is processing RX packets
and accesses the peer structure after its contents have been nulled.

Remove race condition by -
* Flush all RX packets in ol_txrx_peer_detach function which happens
  before peer unmap event is received from firmware
* Avoid use of peer data structures (for example peer->local_id)
  outside of peer->info_lock in ol_rx_data_cb function. Use cached
  local copies of peer data structures instead

Crash signature due to the race condition:

wlan: [0:E :CDF] TXRX: Deleting peer ffffffc012fd13c0
(02:a0:c6:81:f8:c0)
Unable to handle kernel paging request at virtual address 400000001
pgd = ffffffc0018b4000
[400000001] *pgd=0000000000000000, *pud=0000000000000000
Internal error: Oops: 96000005 [#1] PREEMPT SMP
Modules linked in: wlan(O) [last unloaded: wlan]
CPU: 1 PID: 29506 Comm: cds_ol_rx_threa Tainted: G        W  O
3.18.20-g5222edf-13780-g2219ed2 #1
Hardware name: Qualcomm Technologies, Inc. MSM 8996 v3 + PMI8996 CD (DT)
task: ffffffc09350d400 ti: ffffffc0556a4000 task.ti: ffffffc0556a4000
PC is at hdd_rx_packet_cbk+0x84/0x224 [wlan]
LR is at hdd_rx_packet_cbk+0x48/0x224 [wlan]
pc : [<ffffffbffdd55b5c>] lr : [<ffffffbffdd55b20>] pstate: 80000145

Change-Id: I4b32313024ec214f33dcdcfc401aadfa8af9d692
CRs-Fixed: 1002081

core/cds/inc/cds_sched.h

@@ -296,7 +296,6 @@ typedef struct _cds_context_type {
 /*---------------------------------------------------------------------------
    Function declarations and documenation
    ---------------------------------------------------------------------------*/
-
 #ifdef QCA_CONFIG_SMP
 /*---------------------------------------------------------------------------
    \brief cds_drop_rxpkt_by_staid() - API to drop pending Rx packets for a sta
@@ -357,6 +356,70 @@ void cds_free_ol_rx_pkt(p_cds_sched_context pSchedContext,
    \sa cds_free_ol_rx_pkt_freeq()
    -------------------------------------------------------------------------*/
 void cds_free_ol_rx_pkt_freeq(p_cds_sched_context pSchedContext);
+#else
+/**
+ * cds_drop_rxpkt_by_staid() - api to drop pending rx packets for a sta
+ * @pSchedContext: Pointer to the global CDS Sched Context
+ * @staId: Station Id
+ *
+ * This api drops queued packets for a station, to drop all the pending
+ * packets the caller has to send WLAN_MAX_STA_COUNT as staId.
+ *
+ * Return: none
+ */
+static inline
+void cds_drop_rxpkt_by_staid(p_cds_sched_context pSchedContext, uint16_t staId)
+{
+}
+
+/**
+ * cds_indicate_rxpkt() - API to Indicate rx data packet
+ * @pSchedContext: pointer to  CDS Sched Context
+ * @pkt: CDS OL RX pkt pointer containing to RX data message buffer
+ *
+ * Return: none
+ */
+static inline
+void cds_indicate_rxpkt(p_cds_sched_context pSchedContext,
+			struct cds_ol_rx_pkt *pkt)
+{
+}
+
+/**
+ * cds_alloc_ol_rx_pkt() - API to return next available cds message
+ * @pSchedContext: pointer to  CDS Sched Context
+ *
+ * Return: none
+ */
+static inline
+struct cds_ol_rx_pkt *cds_alloc_ol_rx_pkt(p_cds_sched_context pSchedContext)
+{
+}
+
+/**
+ * cds_free_ol_rx_pkt() - API to release cds message to the freeq
+ * @pSchedContext: pointer to  CDS Sched Context
+ * @pkt: CDS message buffer to be returned to free queue
+ *
+ * Return: none
+ */
+static inline
+void cds_free_ol_rx_pkt(p_cds_sched_context pSchedContext,
+			 struct cds_ol_rx_pkt *pkt)
+{
+}
+
+/**
+ * cds_free_ol_rx_pkt_freeq() - Free cds buffer free queue
+ * @pSchedContext: pointer to  CDS Sched Context
+ * @pkt: CDS message buffer to be returned to free queue
+ *
+ * Return: none
+ */
+static inline
+void cds_free_ol_rx_pkt_freeq(p_cds_sched_context pSchedContext)
+{
+}
 #endif
 
 /*---------------------------------------------------------------------------

core/dp/txrx/ol_txrx.c

@@ -2226,6 +2226,62 @@ void ol_txrx_peer_unref_delete(ol_txrx_peer_handle peer)
 	}
 }
 
+/**
+ * ol_txrx_clear_peer_internal() - ol internal function to clear peer
+ * @peer: pointer to ol txrx peer structure
+ *
+ * Return: QDF Status
+ */
+static QDF_STATUS
+ol_txrx_clear_peer_internal(struct ol_txrx_peer_t *peer)
+{
+	p_cds_sched_context sched_ctx = get_cds_sched_ctxt();
+	/* Drop pending Rx frames in CDS */
+	if (sched_ctx)
+		cds_drop_rxpkt_by_staid(sched_ctx, peer->local_id);
+
+	/* Purge the cached rx frame queue */
+	ol_txrx_flush_rx_frames(peer, 1);
+
+	qdf_spin_lock_bh(&peer->peer_info_lock);
+	peer->vdev->rx = NULL;
+	peer->state = OL_TXRX_PEER_STATE_DISC;
+	qdf_spin_unlock_bh(&peer->peer_info_lock);
+
+	return QDF_STATUS_SUCCESS;
+}
+
+/**
+ * ol_txrx_clear_peer() - clear peer
+ * @sta_id: sta id
+ *
+ * Return: QDF Status
+ */
+QDF_STATUS ol_txrx_clear_peer(uint8_t sta_id)
+{
+	struct ol_txrx_peer_t *peer;
+	struct ol_txrx_pdev_t *pdev = cds_get_context(QDF_MODULE_ID_TXRX);
+
+	if (!pdev) {
+		TXRX_PRINT(TXRX_PRINT_LEVEL_ERR, "%s: Unable to find pdev!",
+			   __func__);
+		return QDF_STATUS_E_FAILURE;
+	}
+
+	if (sta_id >= WLAN_MAX_STA_COUNT) {
+		TXRX_PRINT(TXRX_PRINT_LEVEL_ERR, "Invalid sta id %d", sta_id);
+		return QDF_STATUS_E_INVAL;
+	}
+
+
+	peer = ol_txrx_peer_find_by_local_id(pdev, sta_id);
+	if (!peer)
+		return QDF_STATUS_E_FAULT;
+
+	return ol_txrx_clear_peer_internal(peer);
+
+}
+
 /**
  * ol_txrx_peer_detach - Delete a peer's data object.
  * @data_peer - the object to delete
@@ -2245,6 +2301,8 @@ void ol_txrx_peer_detach(ol_txrx_peer_handle peer)
 
 	peer->valid = 0;
 
+	/* flush all rx packets before clearing up the peer local_id */
+	ol_txrx_clear_peer_internal(peer);
 	ol_txrx_local_peer_id_free(peer->vdev->pdev, peer);
 
 	/* debug print to dump rx reorder state */
@@ -2256,7 +2314,6 @@ void ol_txrx_peer_detach(ol_txrx_peer_handle peer)
 		   peer->mac_addr.raw[0], peer->mac_addr.raw[1],
 		   peer->mac_addr.raw[2], peer->mac_addr.raw[3],
 		   peer->mac_addr.raw[4], peer->mac_addr.raw[5]);
-	ol_txrx_flush_rx_frames(peer, 1);
 
 	if (peer->vdev->last_real_peer == peer)
 		peer->vdev->last_real_peer = NULL;
@@ -3455,6 +3512,7 @@ static void ol_rx_data_cb(struct ol_txrx_pdev_t *pdev,
 			  qdf_nbuf_t buf_list, uint16_t staid)
 {
 	void *cds_ctx = cds_get_global_context();
+	void *osif_dev;
 	qdf_nbuf_t buf, next_buf;
 	QDF_STATUS ret;
 	ol_txrx_rx_fp data_rx = NULL;
@@ -3478,6 +3536,7 @@ static void ol_rx_data_cb(struct ol_txrx_pdev_t *pdev,
 	}
 
 	data_rx = peer->vdev->rx;
+	osif_dev = peer->vdev->osif_dev;
 	qdf_spin_unlock_bh(&peer->peer_info_lock);
 
 	qdf_spin_lock_bh(&peer->bufq_lock);
@@ -3492,7 +3551,7 @@ static void ol_rx_data_cb(struct ol_txrx_pdev_t *pdev,
 	while (buf) {
 		next_buf = qdf_nbuf_queue_next(buf);
 		qdf_nbuf_set_next(buf, NULL);   /* Add NULL terminator */
-		ret = data_rx(peer->vdev->osif_dev, buf);
+		ret = data_rx(osif_dev, buf);
 		if (ret != QDF_STATUS_SUCCESS) {
 			TXRX_PRINT(TXRX_PRINT_LEVEL_ERR, "Frame Rx to HDD failed");
 			qdf_nbuf_free(buf);
@@ -3660,52 +3719,6 @@ QDF_STATUS ol_txrx_register_peer(struct ol_txrx_desc_type *sta_desc)
 	return QDF_STATUS_SUCCESS;
 }
 
-/**
- * ol_txrx_clear_peer() - clear peer
- * @sta_id: sta id
- *
- * Return: QDF Status
- */
-QDF_STATUS ol_txrx_clear_peer(uint8_t sta_id)
-{
-	struct ol_txrx_peer_t *peer;
-	struct ol_txrx_pdev_t *pdev = cds_get_context(QDF_MODULE_ID_TXRX);
-
-	if (!pdev) {
-		TXRX_PRINT(TXRX_PRINT_LEVEL_ERR, "%s: Unable to find pdev!",
-			   __func__);
-		return QDF_STATUS_E_FAILURE;
-	}
-
-	if (sta_id >= WLAN_MAX_STA_COUNT) {
-		TXRX_PRINT(TXRX_PRINT_LEVEL_ERR, "Invalid sta id %d", sta_id);
-		return QDF_STATUS_E_INVAL;
-	}
-
-#ifdef QCA_CONFIG_SMP
-	{
-		p_cds_sched_context sched_ctx = get_cds_sched_ctxt();
-		/* Drop pending Rx frames in CDS */
-		if (sched_ctx)
-			cds_drop_rxpkt_by_staid(sched_ctx, sta_id);
-	}
-#endif
-
-	peer = ol_txrx_peer_find_by_local_id(pdev, sta_id);
-	if (!peer)
-		return QDF_STATUS_E_FAULT;
-
-	/* Purge the cached rx frame queue */
-	ol_txrx_flush_rx_frames(peer, 1);
-
-	qdf_spin_lock_bh(&peer->peer_info_lock);
-	peer->vdev->rx = NULL;
-	peer->state = OL_TXRX_PEER_STATE_DISC;
-	qdf_spin_unlock_bh(&peer->peer_info_lock);
-
-	return QDF_STATUS_SUCCESS;
-}
-
 /**
  * ol_txrx_register_ocb_peer - Function to register the OCB peer
  * @cds_ctx: Pointer to the global OS context