pdu_queue must be non-blocking in order to avoid the ue or enb to block in the event of a memory leak and the buffer pool running out of buffers. In that case, the null return shall be handled properly and error logged. This commit restores commit c4c44c33f4.

lib/src/mac/pdu_queue.cc

@@ -27,19 +27,21 @@ uint8_t* pdu_queue::request(uint32_t len)
     ERROR("Error request buffer of invalid size %d. Max bytes %d\n", len, MAX_PDU_LEN);
     return NULL;
   }
-  pdu_t* pdu = pool.allocate("pdu_queue::request", true);
-  if (!pdu) {
+  // This function must be non-blocking. In case we run out of buffers, it shall handle the error properly
+  pdu_t* pdu = pool.allocate("pdu_queue::request", false);
+  if (pdu) {
+    if ((void*)pdu->ptr != (void*)pdu) {
+      ERROR("Fatal error in memory alignment in struct pdu_queue::pdu_t\n");
+      exit(-1);
+    }
+    return pdu->ptr;
+  } else {
     if (log_h) {
       log_h->error("Not enough buffers for MAC PDU\n");
     }
     ERROR("Not enough buffers for MAC PDU\n");
+    return nullptr;
   }
-  if ((void*)pdu->ptr != (void*)pdu) {
-    ERROR("Fatal error in memory alignment in struct pdu_queue::pdu_t\n");
-    exit(-1);
-  }
-
-  return pdu->ptr;
 }
 
 void pdu_queue::deallocate(const uint8_t* pdu)

srsenb/src/stack/mac/mac.cc

@@ -907,7 +907,11 @@ int mac::get_ul_sched(uint32_t tti_tx_ul, ul_sched_list_t& ul_sched_res_list)
               srslte_softbuffer_rx_reset_tbs(phy_ul_sched_res->pusch[n].softbuffer_rx, sched_result.pusch[i].tbs * 8);
             }
             phy_ul_sched_res->pusch[n].data = ue_db[rnti]->request_buffer(sched_result.pusch[i].tbs);
-            phy_ul_sched_res->nof_grants++;
+            if (phy_ul_sched_res->pusch[n].data) {
+              phy_ul_sched_res->nof_grants++;
+            } else {
+              Error("Grant for rnti=0x%x could not be allocated due to lack of buffers\n", rnti);
+            }
             n++;
           } else {
             Warning("Invalid UL scheduling result. User 0x%x does not exist\n", rnti);