dpdk: Change client to wait on member variable

Waiting on queue status seems to not always work, the queue state seems
to not be updated immediately after pushing an item onto it when queried
from a different thread.

1 files changed, 12 insertions, 8 deletions

diff --git a/host/lib/include/uhdlib/transport/dpdk_io_service_client.hpp b/host/lib/include/uhdlib/transport/dpdk_io_service_client.hpp
index 451cc1531..d994fe376 100644
--- a/host/lib/include/uhdlib/transport/dpdk_io_service_client.hpp
+++ b/host/lib/include/uhdlib/transport/dpdk_io_service_client.hpp
@@ -132,7 +132,7 @@ public:
             std::unique_lock<std::mutex> lock(_waiter->mutex);
             wait_req_get(_waiter);
             _waiter->complete = false;
-            auto is_complete  = [this] { return !rte_ring_empty(_buffer_queue); };
+            auto is_complete  = [this] { return _waiter->complete; };
             if (timeout_ms < 0) {
                 _waiter->cond.wait(lock, is_complete);
             } else {
@@ -141,9 +141,11 @@ public:
                     return frame_buff::uptr();
                 }
             }
-            if (rte_ring_dequeue(_buffer_queue, (void**)&buff_ptr)) {
-                return frame_buff::uptr();
-            }
+            // Occasionally the conditional variable wait method returns but the
+            // first dequeue operation fails, even though we push onto it before
+            // setting complete to true. Retrying successfully dequeues a value
+            // in those cases.
+            while (rte_ring_dequeue(_buffer_queue, (void**)&buff_ptr)) {}
         }
         return frame_buff::uptr(buff_ptr);
     }
@@ -240,7 +242,7 @@ public:
             std::unique_lock<std::mutex> lock(_waiter->mutex);
             wait_req_get(_waiter);
             _waiter->complete = false;
-            auto is_complete  = [this] { return !rte_ring_empty(_recv_queue); };
+            auto is_complete  = [this] { return _waiter->complete; };
             if (timeout_ms < 0) {
                 _waiter->cond.wait(lock, is_complete);
             } else {
@@ -249,9 +251,11 @@ public:
                     return frame_buff::uptr();
                 }
             }
-            if (rte_ring_dequeue(_recv_queue, (void**)&buff_ptr)) {
-                return frame_buff::uptr();
-            }
+            // Occasionally the conditional variable wait method returns but the
+            // first dequeue operation fails, even though we push onto it before
+            // setting complete to true. Retrying successfully dequeues a value
+            // in those cases.
+            while (rte_ring_dequeue(_recv_queue, (void**)&buff_ptr)) {}
         }
         return frame_buff::uptr(buff_ptr);
     }