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

fix 7b90e8e:
- add _Atomic specifier to volatile vars used as atomics
- change operations 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

@@ -44,7 +44,7 @@ typedef struct net_bufdesc_ops_ {
 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

@@ -295,7 +295,8 @@ typedef struct
 	/* first 3 same as enet_legacy_desc_t */
 	union {
 		struct {
-			uint16_t len, flags;
+			uint16_t len;
+			uint16_t flags;
 			uint32_t addr;
 		};
 		enet_legacy_desc_t legacy;

drivers/imx-enet.c

@@ -60,7 +60,7 @@ 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;
@@ -384,7 +384,7 @@ static void enet_fillRxDesc(const net_bufdesc_ring_t *ring, size_t i, addr_t pa,
 #if ENET_USE_ENHANCED_DESCRIPTORS
 	desc->yflags = ENET_RXDY_INT;
 #endif
-	atomic_store(&desc->flags, ENET_DESC_RDY | wrap);
+	atomic_store(&desc->flags, ENET_DESC_RDY | wrap); /* NOTE: memory sync */
 }
 
 
@@ -423,7 +423,7 @@ static void enet_fillTxDesc(const net_bufdesc_ring_t *ring, size_t i, addr_t pa,
 	desc->yflags = yflags;
 #endif
 
-	atomic_store(&desc->flags, flags);
+	atomic_store(&desc->flags, flags); /* NOTE: memory sync */
 }
 
 
@@ -480,9 +480,11 @@ static void enet_irq_thread(void *arg)
 {
 	enet_state_t *state = arg;
 	size_t rx_done = 0;
+	unsigned exit;
 
 	mutexLock(state->irq_lock);
-	while (state->drv_exit == 0) {
+	exit = atomic_load(&state->drv_exit);
+	while (exit == 0) {
 		state->mmio->EIR = ENET_IRQ_RXF;
 		rx_done = net_receivePackets(&state->rx, state->netif, ETH_PAD_SIZE);
 		if (rx_done > 0 || net_rxFullyFilled(&state->rx) == 0) {
@@ -497,10 +499,11 @@ static void enet_irq_thread(void *arg)
 			state->mmio->EIMR |= ENET_IRQ_RXF | ENET_IRQ_TXF;
 			condWait(state->irq_cond, state->irq_lock, 0);
 		}
+		exit = atomic_load(&state->drv_exit);
 	}
 	mutexUnlock(state->irq_lock);
 
-	if ((state->drv_exit & EV_BUS_ERROR) != 0) {
+	if ((exit & EV_BUS_ERROR) != 0) {
 		enet_printf(state, "HW signalled memory bus error -- device halted");
 	}
 
@@ -979,6 +982,8 @@ 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;