[dpdk-dev] [PATCH] kni: remove non-C11 path from FIFO sync

[Joyce Kong <joyce.kong@arm.com>]

Non-C11 path was meant to not break build with GCC version < 4.7(when
C11 atomics were introduced), while now minimum GCC version supported
by DPDK has been 4.9, C11 atomics support in compiler is no longer a
problem. So non-C11 path can be removed.

Signed-off-by: Joyce Kong <joyce.kong@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
 lib/kni/rte_kni_common.h |  9 ++------
 lib/kni/rte_kni_fifo.h   | 48 +++++++---------------------------------
 2 files changed, 10 insertions(+), 47 deletions(-)

diff --git a/lib/kni/rte_kni_common.h b/lib/kni/rte_kni_common.h
index b547ea5501..20d94eaa9b 100644
--- a/lib/kni/rte_kni_common.h
+++ b/lib/kni/rte_kni_common.h
@@ -58,13 +58,8 @@ struct rte_kni_request {
  * Writing should never overwrite the read position
  */
 struct rte_kni_fifo {
-#ifdef RTE_USE_C11_MEM_MODEL
-	unsigned write;              /**< Next position to be written*/
-	unsigned read;               /**< Next position to be read */
-#else
-	volatile unsigned write;     /**< Next position to be written*/
-	volatile unsigned read;      /**< Next position to be read */
-#endif
+	unsigned write;     /**< Next position to be written*/
+	unsigned read;      /**< Next position to be read */
 	unsigned len;                /**< Circular buffer length */
 	unsigned elem_size;          /**< Pointer size - for 32/64 bit OS */
 	void *volatile buffer[];     /**< The buffer contains mbuf pointers */
diff --git a/lib/kni/rte_kni_fifo.h b/lib/kni/rte_kni_fifo.h
index d2ec82fe87..057f6b3ded 100644
--- a/lib/kni/rte_kni_fifo.h
+++ b/lib/kni/rte_kni_fifo.h
@@ -2,38 +2,6 @@
  * Copyright(c) 2010-2014 Intel Corporation
  */
 
-
-
-/**
- * @internal when c11 memory model enabled use c11 atomic memory barrier.
- * when under non c11 memory model use rte_smp_* memory barrier.
- *
- * @param src
- *   Pointer to the source data.
- * @param dst
- *   Pointer to the destination data.
- * @param value
- *   Data value.
- */
-#ifdef RTE_USE_C11_MEM_MODEL
-#define __KNI_LOAD_ACQUIRE(src) ({                         \
-		__atomic_load_n((src), __ATOMIC_ACQUIRE);           \
-	})
-#define __KNI_STORE_RELEASE(dst, value) do {               \
-		__atomic_store_n((dst), value, __ATOMIC_RELEASE);   \
-	} while(0)
-#else
-#define __KNI_LOAD_ACQUIRE(src) ({                         \
-		typeof (*(src)) val = *(src);                       \
-		rte_smp_rmb();                                      \
-		val;                                                \
-	})
-#define __KNI_STORE_RELEASE(dst, value) do {               \
-		*(dst) = value;                                     \
-		rte_smp_wmb();                                      \
-	} while(0)
-#endif
-
 /**
  * Initializes the kni fifo structure
  */
@@ -59,7 +27,7 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
 	unsigned i = 0;
 	unsigned fifo_write = fifo->write;
 	unsigned new_write = fifo_write;
-	unsigned fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
+	unsigned fifo_read = __atomic_load_n(&fifo->read, __ATOMIC_ACQUIRE);
 
 	for (i = 0; i < num; i++) {
 		new_write = (new_write + 1) & (fifo->len - 1);
@@ -69,7 +37,7 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
 		fifo->buffer[fifo_write] = data[i];
 		fifo_write = new_write;
 	}
-	__KNI_STORE_RELEASE(&fifo->write, fifo_write);
+	__atomic_store_n(&fifo->write, fifo_write, __ATOMIC_RELEASE);
 	return i;
 }
 
@@ -81,7 +49,7 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
 {
 	unsigned i = 0;
 	unsigned new_read = fifo->read;
-	unsigned fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
+	unsigned fifo_write = __atomic_load_n(&fifo->write, __ATOMIC_ACQUIRE);
 
 	for (i = 0; i < num; i++) {
 		if (new_read == fifo_write)
@@ -90,7 +58,7 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
 		data[i] = fifo->buffer[new_read];
 		new_read = (new_read + 1) & (fifo->len - 1);
 	}
-	__KNI_STORE_RELEASE(&fifo->read, new_read);
+	__atomic_store_n(&fifo->read, new_read, __ATOMIC_RELEASE);
 	return i;
 }
 
@@ -100,8 +68,8 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
 static inline uint32_t
 kni_fifo_count(struct rte_kni_fifo *fifo)
 {
-	unsigned fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
-	unsigned fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
+	unsigned fifo_write = __atomic_load_n(&fifo->write, __ATOMIC_ACQUIRE);
+	unsigned fifo_read = __atomic_load_n(&fifo->read, __ATOMIC_ACQUIRE);
 	return (fifo->len + fifo_write - fifo_read) & (fifo->len - 1);
 }
 
@@ -111,7 +79,7 @@ kni_fifo_count(struct rte_kni_fifo *fifo)
 static inline uint32_t
 kni_fifo_free_count(struct rte_kni_fifo *fifo)
 {
-	uint32_t fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
-	uint32_t fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
+	uint32_t fifo_write = __atomic_load_n(&fifo->write, __ATOMIC_ACQUIRE);
+	uint32_t fifo_read = __atomic_load_n(&fifo->read, __ATOMIC_ACQUIRE);
 	return (fifo_read - fifo_write - 1) & (fifo->len - 1);
 }
-- 
2.17.1