drivers/(bdring, imx-enet): fix 7b90e8e: improve atomic semantics

add _Atomic specifier to volatile vars used as atomic
change every operation on the vars to atomic_*
JIRA: RTOS-507

drivers/bdring.c

@@ -107,7 +107,8 @@ int net_initRings(net_bufdesc_ring_t *rings, const size_t *sizes, size_t nrings,
 	for (i = 0; i < nrings; ++i) {
 		rings[i].ring = p;
 		rings[i].bufp = bufp;
-		rings[i].head = rings[i].tail = 0;
+		atomic_init(&rings[i].head, 0);
+		atomic_init(&rings[i].tail, 0);
 		rings[i].last = sizes[i] - 1;
 		rings[i].phys = phys;
 		rings[i].ops = ops;
@@ -131,11 +132,11 @@ size_t net_receivePackets(net_bufdesc_ring_t *ring, struct netif *ni, unsigned e
 
 	mutexLock(ring->lock);
 	n = 0;
-	i = ring->head;
+	i = atomic_load(&ring->head);
 	pkt = NULL;
 
 	for (;;) {
-		if (i == ring->tail) {
+		if (i == atomic_load(&ring->tail)) {
 			break;
 		}
 
@@ -172,7 +173,7 @@ size_t net_receivePackets(net_bufdesc_ring_t *ring, struct netif *ni, unsigned e
 		++n;
 	}
 
-	ring->head = i;
+	atomic_store(&ring->head, i);
 	mutexUnlock(ring->lock);
 	return n;
 }
@@ -190,7 +191,7 @@ size_t net_refillRx(net_bufdesc_ring_t *ring, size_t ethpad)
 	nxt = (i + 1) & ring->last;	 // NOTE: 2^n ring size verified in net_initRings
 	sz = ring->ops->pkt_buf_sz;
 
-	while (nxt != ring->head) {
+	while (nxt != atomic_load(&ring->head)) {
 		p = net_allocDMAPbuf(&pa, sz);
 		if (p == NULL) {
 			break;
@@ -206,7 +207,7 @@ size_t net_refillRx(net_bufdesc_ring_t *ring, size_t ethpad)
 		++n;
 	}
 
-	ring->tail = i;
+	atomic_store(&ring->tail, i);
 	mutexUnlock(ring->lock);
 	return n;
 }
@@ -218,7 +219,7 @@ size_t net_reapTxFinished(net_bufdesc_ring_t *ring)
 	mutexLock(ring->lock);
 
 	n = 0;
-	i = ring->tail;
+	i = atomic_load(&ring->tail);
 	head = atomic_load(&ring->head);
 	while (i != head) {
 		if (ring->ops->nextTxDone(ring, i) == 0) {
@@ -295,7 +296,7 @@ size_t net_transmitPacket(net_bufdesc_ring_t *ring, struct pbuf *p)
 	mutexLock(ring->lock);
 	// NOTE: 2^n ring size verified in net_initRings
 	n = atomic_load(&ring->tail);	// access tail once - it may be advanced by tx_done thread
-	i = ring->head;
+	i = atomic_load(&ring->head);
 	n = (n - i - 1) & ring->last;
 	if (n > MAX_TX_FRAGMENTS) {
 		n = MAX_TX_FRAGMENTS;

drivers/bdring.h

@@ -46,7 +46,7 @@ struct net_bufdesc_ring_
 {
 	volatile void *ring;
 	struct pbuf **bufp;
-	volatile unsigned head, tail;
+	_Atomic volatile unsigned head, tail;
 	unsigned last;
 	addr_t phys;
 	const net_bufdesc_ops_t *ops;

drivers/imx-enet-regs.h

@@ -308,7 +308,7 @@ struct enet_regs {
 typedef struct
 {
 	uint16_t len; /* for last frag = whole frame size? (TBV) */
-	uint16_t flags;
+	_Atomic volatile uint16_t flags;
 	uint32_t addr; /* 64B-aligned buffer [size = TRUNC_FL ?] */
 } enet_legacy_desc_t;
 
@@ -317,7 +317,8 @@ typedef struct
 	/* first 3 same as enet_short_desc_t */
 	union {
 		struct {
-			uint16_t len, flags;
+			uint16_t len;
+			_Atomic volatile uint16_t flags;
 			uint32_t addr;
 		};
 		enet_legacy_desc_t legacy;

drivers/imx-enet.c

@@ -45,7 +45,7 @@ typedef struct
 	volatile struct enet_regs *mmio;
 
 	struct netif *netif;
-	unsigned drv_exit;
+	_Atomic volatile unsigned drv_exit;
 
 #define PRIV_RESOURCES(s) &(s)->irq_lock, 3, ~0x03
 	handle_t irq_lock, tx_lock;
@@ -374,7 +374,7 @@ static size_t enet_nextRxBufferSize(const net_bufdesc_ring_t *ring, size_t i)
 	}
 #endif
 
-	if ((desc->flags & ENET_DESC_RDY) != 0) {
+	if ((atomic_load(&desc->flags) & ENET_DESC_RDY) != 0) {
 		return 0;
 	}
 
@@ -392,7 +392,7 @@ static int enet_pktRxFinished(const net_bufdesc_ring_t *ring, size_t i)
 {
 	volatile enet_buf_desc_t *desc = (volatile enet_buf_desc_t *)ring->ring + i;
 
-	return desc->flags & ENET_DESC_LAST;
+	return atomic_load(&desc->flags) & ENET_DESC_LAST;
 }
 
 
@@ -414,7 +414,7 @@ static int enet_nextTxDone(const net_bufdesc_ring_t *ring, size_t i)
 {
 	volatile enet_buf_desc_t *desc = (volatile enet_buf_desc_t *)ring->ring + i;
 
-	return !(desc->flags & ENET_DESC_RDY);
+	return !(atomic_load(&desc->flags) & ENET_DESC_RDY);
 }
 
 
@@ -1012,6 +1012,8 @@ static int enet_initDevice(enet_state_t *state, int irq, int mdio)
 		return err;
 	}
 
+	atomic_init(&state->drv_exit, 0x0);
+
 	err = enet_clockEnable(state);
 	if (err < 0) {
 		return err;