kni: introduce C11 atomic into FIFO synchronization

Syncing the values by adding c11 atomic memory barriers to make sure
the values being synced before updating fifo_write and fifo_read.

Signed-off-by: Phil Yang <phil.yang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Ola Liljedahl <ola.liljedahl@arm.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
index 58e8533..5afa087 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
+++ b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h
@@ -55,8 +55,13 @@ 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 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/librte_kni/rte_kni_fifo.h b/lib/librte_kni/rte_kni_fifo.h
index 70ac14e..287d7de 100644 (file)
--- a/lib/librte_kni/rte_kni_fifo.h
+++ b/lib/librte_kni/rte_kni_fifo.h
@@ -4,6 +4,36 @@
 
 
 
+/**
+ * @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
  */
@@ -29,8 +59,7 @@ 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;
-       rte_smp_rmb();
-       unsigned fifo_read = fifo->read;
+       unsigned fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
 
        for (i = 0; i < num; i++) {
                new_write = (new_write + 1) & (fifo->len - 1);
@@ -40,8 +69,7 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
                fifo->buffer[fifo_write] = data[i];
                fifo_write = new_write;
        }
-       rte_smp_wmb();
-       fifo->write = fifo_write;
+       __KNI_STORE_RELEASE(&fifo->write, fifo_write);
        return i;
 }
 
@@ -53,8 +81,7 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
 {
        unsigned i = 0;
        unsigned new_read = fifo->read;
-       rte_smp_rmb();
-       unsigned fifo_write = fifo->write;
+       unsigned fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
 
        for (i = 0; i < num; i++) {
                if (new_read == fifo_write)
@@ -63,8 +90,7 @@ 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);
        }
-       rte_smp_rmb();
-       fifo->read = new_read;
+       __KNI_STORE_RELEASE(&fifo->read, new_read);
        return i;
 }
 
@@ -74,8 +100,7 @@ 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 = fifo->write;
-       rte_smp_rmb();
-       unsigned fifo_read = fifo->read;
+       unsigned fifo_write = __KNI_LOAD_ACQUIRE(&fifo->write);
+       unsigned fifo_read = __KNI_LOAD_ACQUIRE(&fifo->read);
        return (fifo->len + fifo_write - fifo_read) & (fifo->len - 1);
 }