From b29fd449d0fa231c87a3c353adc89ed31e631521 Mon Sep 17 00:00:00 2001
From: Melissa Elkadi <melissa@episci.com>
Date: Tue, 2 Nov 2021 14:35:32 -0700
Subject: [PATCH] Changed ul_tti_req queueing mechanism:

Instead of resetting queue when full,
take last item out.
---
 openair2/NR_UE_PHY_INTERFACE/NR_IF_Module.c | 13 ++--------
 openair2/PHY_INTERFACE/queue.c              | 28 +++++++++++++++++++++
 openair2/PHY_INTERFACE/queue.h              |  1 +
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/openair2/NR_UE_PHY_INTERFACE/NR_IF_Module.c b/openair2/NR_UE_PHY_INTERFACE/NR_IF_Module.c
index c2d7e341bf..9dc6cf918f 100644
--- a/openair2/NR_UE_PHY_INTERFACE/NR_IF_Module.c
+++ b/openair2/NR_UE_PHY_INTERFACE/NR_IF_Module.c
@@ -752,18 +752,9 @@ static void enqueue_nr_nfapi_msg(void *buffer, ssize_t len, nfapi_p7_message_hea
             {
                 LOG_D(NR_MAC, "We added UL_TTI_REQ to queue for sfn slot %d %d\n",
                       ul_tti_request->SFN, ul_tti_request->Slot);
-                if (!put_queue(&nr_wait_ul_tti_req_queue, ul_tti_request))
-                {
-                    reset_queue(&nr_wait_ul_tti_req_queue);
-                    if (!put_queue(&nr_wait_ul_tti_req_queue, ul_tti_request))
-                    {
-                        LOG_E(NR_PHY, "put_queue failed for nr_wait_ul_tti_req_queue.\n");
-                        free(ul_tti_request);
-                        ul_tti_request = NULL;
-                    }
-                }
+                nfapi_nr_ul_tti_request_t *evicted_ul_tti_req = put_queue_replace(&nr_wait_ul_tti_req_queue, ul_tti_request);
+                free(evicted_ul_tti_req);
             }
-
             break;
         }
 
diff --git a/openair2/PHY_INTERFACE/queue.c b/openair2/PHY_INTERFACE/queue.c
index c6e1fb6d2f..d837857ac7 100644
--- a/openair2/PHY_INTERFACE/queue.c
+++ b/openair2/PHY_INTERFACE/queue.c
@@ -25,6 +25,34 @@ void reset_queue(queue_t *q)
   }
 }
 
+void *put_queue_replace(queue_t *q, void *item)
+{
+    assert(item != NULL);
+    if (pthread_mutex_lock(&q->mutex) != 0)
+    {
+        LOG_ERROR("put_queue: mutex_lock failed");
+        return false;
+    }
+
+    void *evicted = NULL;
+    if (q->num_items >= MAX_QUEUE_SIZE)
+    {
+        evicted = q->items[q->read_index];
+        assert(evicted != NULL);
+        q->items[q->read_index] = NULL;
+        q->read_index = (q->read_index + 1) % MAX_QUEUE_SIZE;
+        q->num_items--;
+    }
+    assert(q->items[q->write_index] == NULL);
+    q->items[q->write_index] = item;
+    q->write_index = (q->write_index + 1) % MAX_QUEUE_SIZE;
+    q->num_items++;
+
+    pthread_mutex_unlock(&q->mutex);
+    return evicted;
+}
+
+
 bool put_queue(queue_t *q, void *item)
 {
     assert(item != NULL);
diff --git a/openair2/PHY_INTERFACE/queue.h b/openair2/PHY_INTERFACE/queue.h
index d274f7b0cd..4678e31030 100644
--- a/openair2/PHY_INTERFACE/queue.h
+++ b/openair2/PHY_INTERFACE/queue.h
@@ -42,6 +42,7 @@ typedef struct queue_t
 
 void init_queue(queue_t *q);
 void reset_queue(queue_t *q);
+void *put_queue_replace(queue_t *q, void *item);
 bool put_queue(queue_t *q, void *item);
 void *get_queue(queue_t *q);