caif-shm: Fix deadlock caused due to improper locking

Improper usage of spin lock, which leads to deadlock.

Tx: acquire_lock1 -> trying to acquire lock2
Rx: acquire_lock2 -> trying to acquire lock1

Fix: locking was done through out the function which is not required.
Only in placed where list has be accessed or modified locking is required.

ST-Ericsson Linux next: NA
ST-Ericsson ID: 360284
ST-Ericsson FOSS-OUT ID: Trivial

Change-Id: I962fcb35f44b6030d6f1151f118d35e328b69156
Signed-off-by: Arun Murthy <arun.murthy@stericsson.com>
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/30980
Reviewed-by: Hemant-vilas RAMDASI <hemant.ramdasi@stericsson.com>
Tested-by: Hemant-vilas RAMDASI <hemant.ramdasi@stericsson.com>
Reviewed-by: Durga Prasada Rao BATHINA <durgaprasadarao.b@stericsson.com>

1 files changed, 5 insertions, 7 deletions

diff --git a/drivers/net/caif/caif_shmcore.c b/drivers/net/caif/caif_shmcore.c
index d4b26fb24ed..27392cd05fd 100644
--- a/drivers/net/caif/caif_shmcore.c
+++ b/drivers/net/caif/caif_shmcore.c
@@ -238,11 +238,11 @@ int caif_shmdrv_rx_cb(u32 mbx_msg, void *priv)
 		if ((avail_emptybuff > HIGH_WATERMARK) &&
 					(!pshm_drv->tx_empty_available)) {
 			pshm_drv->tx_empty_available = 1;
+			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 			pshm_drv->cfdev.flowctrl
 					(pshm_drv->pshm_dev->pshm_netdev,
 								CAIF_FLOW_ON);
 
-			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 
 			/* Schedule the work queue. if required */
 			if (!work_pending(&pshm_drv->shm_tx_work))
@@ -285,6 +285,7 @@ static void shm_rx_work_func(struct work_struct *rx_work)
 			list_entry(pshm_drv->rx_full_list.next, struct buf_list,
 					list);
 		list_del_init(&pbuf->list);
+		spin_unlock_irqrestore(&pshm_drv->lock, flags);
 
 		/* Retrieve pointer to start of the packet descriptor area. */
 		pck_desc = (struct shm_pck_desc *) pbuf->desc_vptr;
@@ -360,6 +361,7 @@ static void shm_rx_work_func(struct work_struct *rx_work)
 			pck_desc++;
 		}
 
+		spin_lock_irqsave(&pshm_drv->lock, flags);
 		list_add_tail(&pbuf->list, &pshm_drv->rx_pend_list);
 
 		spin_unlock_irqrestore(&pshm_drv->lock, flags);
@@ -412,7 +414,6 @@ static void shm_tx_work_func(struct work_struct *tx_work)
 
 		if (skb == NULL)
 			goto send_msg;
-
 		/* Check the available no. of buffers in the empty list */
 		list_for_each(pos, &pshm_drv->tx_empty_list)
 			avail_emptybuff++;
@@ -421,9 +422,11 @@ static void shm_tx_work_func(struct work_struct *tx_work)
 					pshm_drv->tx_empty_available) {
 			/* Update blocking condition. */
 			pshm_drv->tx_empty_available = 0;
+			spin_unlock_irqrestore(&pshm_drv->lock, flags);
 			pshm_drv->cfdev.flowctrl
 					(pshm_drv->pshm_dev->pshm_netdev,
 					CAIF_FLOW_OFF);
+			spin_lock_irqsave(&pshm_drv->lock, flags);
 		}
 		/*
 		 * We simply return back to the caller if we do not have space
@@ -512,16 +515,11 @@ send_msg:
 static int shm_netdev_tx(struct sk_buff *skb, struct net_device *shm_netdev)
 {
 	struct shmdrv_layer *pshm_drv;
-	unsigned long flags = 0;
 
 	pshm_drv = netdev_priv(shm_netdev);
 
-	spin_lock_irqsave(&pshm_drv->lock, flags);
-
 	skb_queue_tail(&pshm_drv->sk_qhead, skb);
 
-	spin_unlock_irqrestore(&pshm_drv->lock, flags);
-
 	/* Schedule Tx work queue. for deferred processing of skbs*/
 	if (!work_pending(&pshm_drv->shm_tx_work))
 		queue_work(pshm_drv->pshm_tx_workqueue, &pshm_drv->shm_tx_work);