enb: fix race condition in workers overwriting the DL tx buffer

this adds a own tx buffer for each HARQ PID

srsenb/hdr/stack/mac/ue.h

@@ -46,9 +46,13 @@ public:
   void     set_tti(uint32_t tti); 
   
   void     config(uint16_t rnti, uint32_t nof_prb, sched_interface *sched, rrc_interface_mac *rrc_, rlc_interface_mac *rlc, srslte::log *log_h);
-  uint8_t* generate_pdu(uint32_t tb_idx, sched_interface::dl_sched_pdu_t pdu[sched_interface::MAX_RLC_PDU_LIST],
+  uint8_t* generate_pdu(uint32_t                        harq_pid,
-                    uint32_t nof_pdu_elems, uint32_t grant_size);
+                        uint32_t                        tb_idx,
-  uint8_t* generate_mch_pdu(sched_interface::dl_pdu_mch_t sched, uint32_t nof_pdu_elems, uint32_t grant_size);
+                        sched_interface::dl_sched_pdu_t pdu[sched_interface::MAX_RLC_PDU_LIST],
+                        uint32_t                        nof_pdu_elems,
+                        uint32_t                        grant_size);
+  uint8_t*
+  generate_mch_pdu(uint32_t harq_pid, sched_interface::dl_pdu_mch_t sched, uint32_t nof_pdu_elems, uint32_t grant_size);
 
   srslte_softbuffer_tx_t* get_tx_softbuffer(uint32_t harq_process, uint32_t tb_idx);
   srslte_softbuffer_rx_t* get_rx_softbuffer(uint32_t tti);
@@ -107,7 +111,7 @@ private:
   uint8_t* pending_buffers[NOF_RX_HARQ_PROCESSES];
 
   // For DL there are two buffers, one for each Transport block
-  srslte::byte_buffer_t tx_payload_buffer[SRSLTE_MAX_TB];
+  srslte::byte_buffer_t tx_payload_buffer[SRSLTE_FDD_NOF_HARQ][SRSLTE_MAX_TB];
 
   // For UL there are multiple buffers per PID and are managed by pdu_queue
   srslte::pdu_queue pdus; 

srsenb/src/stack/mac/mac.cc

@@ -570,8 +570,11 @@ int mac::get_dl_sched(uint32_t tti, dl_sched_t *dl_sched_res)
 
         if (sched_result.data[i].nof_pdu_elems[tb] > 0) {
           /* Get PDU if it's a new transmission */
-          dl_sched_res->pdsch[n].data[tb] = ue_db[rnti]->generate_pdu(
+          dl_sched_res->pdsch[n].data[tb] = ue_db[rnti]->generate_pdu(sched_result.data[i].dci.pid,
-              tb, sched_result.data[i].pdu[tb], sched_result.data[i].nof_pdu_elems[tb], sched_result.data[i].tbs[tb]);
+                                                                      tb,
+                                                                      sched_result.data[i].pdu[tb],
+                                                                      sched_result.data[i].nof_pdu_elems[tb],
+                                                                      sched_result.data[i].tbs[tb]);
 
           if (!dl_sched_res->pdsch[n].data[tb]) {
             Error("Error! PDU was not generated (rnti=0x%04x, tb=%d)\n", rnti, tb);
@@ -711,7 +714,10 @@ int mac::get_mch_sched(uint32_t tti, bool is_mcch, dl_sched_t* dl_sched_res)
     mch.pdu[mch.num_mtch_sched].lcid = 0;
     mch.pdu[mch.num_mtch_sched].nbytes = current_mcch_length;
     dl_sched_res->pdsch[0].dci.rnti    = SRSLTE_MRNTI;
-    dl_sched_res->pdsch[0].data[0] = ue_db[SRSLTE_MRNTI]->generate_mch_pdu(mch, mch.num_mtch_sched + 1, mcs.tbs / 8);
+
+    // we use TTI % HARQ to make sure we use different buffers for consecutive TTIs to avoid races between PHY workers
+    dl_sched_res->pdsch[0].data[0] =
+        ue_db[SRSLTE_MRNTI]->generate_mch_pdu(tti % SRSLTE_FDD_NOF_HARQ, mch, mch.num_mtch_sched + 1, mcs.tbs / 8);
 
   } else {
     uint32_t current_lcid = 1;
@@ -733,7 +739,8 @@ int mac::get_mch_sched(uint32_t tti, bool is_mcch, dl_sched_t* dl_sched_res)
       mch.mtch_sched[0].mtch_payload  = mtch_payload_buffer;
       dl_sched_res->pdsch[0].dci.rnti = SRSLTE_MRNTI;
       if (bytes_received) {
-        dl_sched_res->pdsch[0].data[0] = ue_db[SRSLTE_MRNTI]->generate_mch_pdu(mch, 1, mcs_data.tbs / 8);
+        dl_sched_res->pdsch[0].data[0] =
+            ue_db[SRSLTE_MRNTI]->generate_mch_pdu(tti % SRSLTE_FDD_NOF_HARQ, mch, 1, mcs_data.tbs / 8);
       }
     } else {
       dl_sched_res->pdsch[0].dci.rnti = 0;

srsenb/src/stack/mac/ue.cc

@@ -409,14 +409,17 @@ void ue::allocate_ce(srslte::sch_pdu *pdu, uint32_t lcid)
   }
 }
 
-uint8_t* ue::generate_pdu(uint32_t tb_idx, sched_interface::dl_sched_pdu_t pdu[sched_interface::MAX_RLC_PDU_LIST],
+uint8_t* ue::generate_pdu(uint32_t                        harq_pid,
-                      uint32_t nof_pdu_elems, uint32_t grant_size)
+                          uint32_t                        tb_idx,
+                          sched_interface::dl_sched_pdu_t pdu[sched_interface::MAX_RLC_PDU_LIST],
+                          uint32_t                        nof_pdu_elems,
+                          uint32_t                        grant_size)
 {
   uint8_t *ret = NULL; 
   pthread_mutex_lock(&mutex);
   if (rlc) {
-    tx_payload_buffer->clear();
+    tx_payload_buffer[harq_pid][tb_idx].clear();
-    mac_msg_dl.init_tx(&tx_payload_buffer[tb_idx], grant_size, false);
+    mac_msg_dl.init_tx(&tx_payload_buffer[harq_pid][tb_idx], grant_size, false);
     for (uint32_t i=0;i<nof_pdu_elems;i++) {
       if (pdu[i].lcid <= srslte::sch_subh::PHR_REPORT) {
         allocate_sdu(&mac_msg_dl, pdu[i].lcid, pdu[i].nbytes);
@@ -435,12 +438,15 @@ uint8_t* ue::generate_pdu(uint32_t tb_idx, sched_interface::dl_sched_pdu_t pdu[s
   return ret; 
 }
 
-uint8_t* ue::generate_mch_pdu(sched_interface::dl_pdu_mch_t sched, uint32_t nof_pdu_elems , uint32_t grant_size)
+uint8_t* ue::generate_mch_pdu(uint32_t                      harq_pid,
+                              sched_interface::dl_pdu_mch_t sched,
+                              uint32_t                      nof_pdu_elems,
+                              uint32_t                      grant_size)
 {
   uint8_t *ret = NULL; 
   pthread_mutex_lock(&mutex);
-  tx_payload_buffer->clear();
+  tx_payload_buffer[harq_pid][0].clear();
-  mch_mac_msg_dl.init_tx(&tx_payload_buffer[0], grant_size);
+  mch_mac_msg_dl.init_tx(&tx_payload_buffer[harq_pid][0], grant_size);
 
   for (uint32_t i = 0; i < nof_pdu_elems; i++) {
     if (sched.pdu[i].lcid == srslte::mch_subh::MCH_SCHED_INFO) {