1 files changed, 18 insertions, 6 deletions

diff --git a/kernel/linux/kni/kni_fifo.h b/kernel/linux/kni/kni_fifo.h
index 9a4762de..3f4781c2 100644
--- a/kernel/linux/kni/kni_fifo.h
+++ b/kernel/linux/kni/kni_fifo.h
@@ -8,6 +8,14 @@
 
 #include <exec-env/rte_kni_common.h>
 
+/* Skip some memory barriers on Linux < 3.14 */
+#ifndef smp_load_acquire
+#define smp_load_acquire(a) (*(a))
+#endif
+#ifndef smp_store_release
+#define smp_store_release(a, b) *(a) = (b)
+#endif
+
 /**
  * Adds num elements into the fifo. Return the number actually written
  */
@@ -16,7 +24,7 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, uint32_t num)
 {
 	uint32_t i = 0;
 	uint32_t fifo_write = fifo->write;
-	uint32_t fifo_read = fifo->read;
+	uint32_t fifo_read = smp_load_acquire(&fifo->read);
 	uint32_t new_write = fifo_write;
 
 	for (i = 0; i < num; i++) {
@@ -27,7 +35,7 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, uint32_t num)
 		fifo->buffer[fifo_write] = data[i];
 		fifo_write = new_write;
 	}
-	fifo->write = fifo_write;
+	smp_store_release(&fifo->write, fifo_write);
 
 	return i;
 }
@@ -40,7 +48,7 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, uint32_t num)
 {
 	uint32_t i = 0;
 	uint32_t new_read = fifo->read;
-	uint32_t fifo_write = fifo->write;
+	uint32_t fifo_write = smp_load_acquire(&fifo->write);
 
 	for (i = 0; i < num; i++) {
 		if (new_read == fifo_write)
@@ -49,7 +57,7 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, uint32_t num)
 		data[i] = fifo->buffer[new_read];
 		new_read = (new_read + 1) & (fifo->len - 1);
 	}
-	fifo->read = new_read;
+	smp_store_release(&fifo->read, new_read);
 
 	return i;
 }
@@ -60,7 +68,9 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, uint32_t num)
 static inline uint32_t
 kni_fifo_count(struct rte_kni_fifo *fifo)
 {
-	return (fifo->len + fifo->write - fifo->read) & (fifo->len - 1);
+	uint32_t fifo_write = smp_load_acquire(&fifo->write);
+	uint32_t fifo_read = smp_load_acquire(&fifo->read);
+	return (fifo->len + fifo_write - fifo_read) & (fifo->len - 1);
 }
 
 /**
@@ -69,7 +79,9 @@ kni_fifo_count(struct rte_kni_fifo *fifo)
 static inline uint32_t
 kni_fifo_free_count(struct rte_kni_fifo *fifo)
 {
-	return (fifo->read - fifo->write - 1) & (fifo->len - 1);
+	uint32_t fifo_write = smp_load_acquire(&fifo->write);
+	uint32_t fifo_read = smp_load_acquire(&fifo->read);
+	return (fifo_read - fifo_write - 1) & (fifo->len - 1);
 }
 
 #endif /* _KNI_FIFO_H_ */