[dpdk-dev] [PATCH v2 2/3] kni: fix kni fifo synchronization
Phil Yang
phil.yang at arm.com
Wed Sep 19 15:42:39 CEST 2018
With existing code in kni_fifo_put, rx_q values are not being updated
before updating fifo_write. While reading rx_q in kni_net_rx_normal,
This is causing the sync issue on other core. The same situation happens
in kni_fifo_get as well.
So syncing the values by adding C11 atomic memory barriers to make sure
the values being synced before updating fifo_write and fifo_read.
Fixes: 3fc5ca2 ("kni: initial import")
Signed-off-by: Phil Yang <phil.yang at arm.com>
Reviewed-by: Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>
Reviewed-by: Gavin Hu <Gavin.Hu at arm.com>
---
.../linuxapp/eal/include/exec-env/rte_kni_common.h | 5 ++++
lib/librte_kni/rte_kni_fifo.h | 30 +++++++++++++++++++++-
2 files changed, 34 insertions(+), 1 deletion(-)
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 cfa9448..1fd713b 100644
--- 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
@@ -54,8 +54,13 @@ struct rte_kni_request {
* Writing should never overwrite the read position
*/
struct rte_kni_fifo {
+#ifndef RTE_USE_C11_MEM_MODEL
volatile unsigned write; /**< Next position to be written*/
volatile unsigned read; /**< Next position to be read */
+#else
+ unsigned write; /**< Next position to be written*/
+ 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 ac26a8c..f4171a1 100644
--- a/lib/librte_kni/rte_kni_fifo.h
+++ b/lib/librte_kni/rte_kni_fifo.h
@@ -28,8 +28,13 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
{
unsigned i = 0;
unsigned fifo_write = fifo->write;
- unsigned fifo_read = fifo->read;
unsigned new_write = fifo_write;
+#ifdef RTE_USE_C11_MEM_MODEL
+ unsigned fifo_read = __atomic_load_n(&fifo->read,
+ __ATOMIC_ACQUIRE);
+#else
+ unsigned fifo_read = fifo->read;
+#endif
for (i = 0; i < num; i++) {
new_write = (new_write + 1) & (fifo->len - 1);
@@ -39,7 +44,12 @@ kni_fifo_put(struct rte_kni_fifo *fifo, void **data, unsigned num)
fifo->buffer[fifo_write] = data[i];
fifo_write = new_write;
}
+#ifdef RTE_USE_C11_MEM_MODEL
+ __atomic_store_n(&fifo->write, fifo_write, __ATOMIC_RELEASE);
+#else
+ rte_smp_wmb();
fifo->write = fifo_write;
+#endif
return i;
}
@@ -51,7 +61,12 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
{
unsigned i = 0;
unsigned new_read = fifo->read;
+#ifdef RTE_USE_C11_MEM_MODEL
+ unsigned fifo_write = __atomic_load_n(&fifo->write, __ATOMIC_ACQUIRE);
+#else
unsigned fifo_write = fifo->write;
+#endif
+
for (i = 0; i < num; i++) {
if (new_read == fifo_write)
break;
@@ -59,7 +74,12 @@ 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);
}
+#ifdef RTE_USE_C11_MEM_MODEL
+ __atomic_store_n(&fifo->read, new_read, __ATOMIC_RELEASE);
+#else
+ rte_smp_wmb();
fifo->read = new_read;
+#endif
return i;
}
@@ -69,5 +89,13 @@ kni_fifo_get(struct rte_kni_fifo *fifo, void **data, unsigned num)
static inline uint32_t
kni_fifo_count(struct rte_kni_fifo *fifo)
{
+#ifdef RTE_USE_C11_MEM_MODEL
+ 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);
+#else
return (fifo->len + fifo->write - fifo->read) & (fifo->len - 1);
+#endif
}
--
2.7.4
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