[v3,4/4] kni: introduce c11 atomic into kni fifo synchronization
Checks
Commit Message
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>
---
.../linuxapp/eal/include/exec-env/rte_kni_common.h | 5 +++
lib/librte_kni/rte_kni_fifo.h | 47 +++++++++++++++++-----
2 files changed, 41 insertions(+), 11 deletions(-)
@@ -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 */
@@ -5,6 +5,36 @@
/**
+ * @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
*/
static void
@@ -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);
}