enb,mac: protect concurrent access to ue_db from different threads

race condition between PHY worker(s) and Stack thread when
accessing ue_db member. RWlock needs to be hold.

partly fixes #2932

srsenb/src/stack/mac/mac.cc

@@ -126,6 +126,7 @@ void mac::reset()
 
 void mac::start_pcap(srsran::mac_pcap* pcap_)
 {
+  srsran::rwlock_read_guard lock(rwlock);
   pcap = pcap_;
   // Set pcap in all UEs for UL messages
   for (auto& u : ue_db) {
@@ -135,6 +136,7 @@ void mac::start_pcap(srsran::mac_pcap* pcap_)
 
 void mac::start_pcap_net(srsran::mac_pcap_net* pcap_net_)
 {
+  srsran::rwlock_read_guard lock(rwlock);
   pcap_net = pcap_net_;
   // Set pcap in all UEs for UL messages
   for (auto& u : ue_db) {
@@ -292,6 +294,7 @@ void mac::toggle_padding()
 
 void mac::add_padding()
 {
+  srsran::rwlock_read_guard lock(rwlock);
   for (auto it = ue_db.begin(); it != ue_db.end(); ++it) {
     uint16_t cur_rnti = it->first;
     auto     ue       = it;
@@ -817,6 +820,7 @@ void mac::build_mch_sched(uint32_t tbs)
 
 int mac::get_mch_sched(uint32_t tti, bool is_mcch, dl_sched_list_t& dl_sched_res_list)
 {
+  srsran::rwlock_read_guard lock(rwlock);
   dl_sched_t* dl_sched_res = &dl_sched_res_list[0];
   logger.set_context(tti);
   srsran_ra_tb_t mcs      = {};
@@ -930,6 +934,8 @@ int mac::get_ul_sched(uint32_t tti_tx_ul, ul_sched_list_t& ul_sched_res_list)
 
   logger.set_context(TTI_SUB(tti_tx_ul, FDD_HARQ_DELAY_UL_MS + FDD_HARQ_DELAY_DL_MS));
 
+  srsran::rwlock_read_guard lock(rwlock);
+
   // Execute UE FSMs (e.g. TA)
   for (auto& ue : ue_db) {
     ue.second->tic();
@@ -945,9 +951,6 @@ int mac::get_ul_sched(uint32_t tti_tx_ul, ul_sched_list_t& ul_sched_res_list)
       return SRSRAN_ERROR;
     }
 
-    {
-      srsran::rwlock_read_guard lock(rwlock);
-
     // Copy DCI grants
     phy_ul_sched_res->nof_grants = 0;
     int n                        = 0;
@@ -990,9 +993,6 @@ int mac::get_ul_sched(uint32_t tti_tx_ul, ul_sched_list_t& ul_sched_res_list)
       }
     }
 
-      // No more uses of ue_db beyond here
-    }
-
     // Copy PHICH actions
     for (uint32_t i = 0; i < sched_result.phich.size(); i++) {
       phy_ul_sched_res->phich[i].ack  = sched_result.phich[i].phich == sched_interface::ul_sched_phich_t::ACK;
@@ -1023,6 +1023,7 @@ void mac::write_mcch(const srsran::sib2_mbms_t* sib2_,
                      const uint8_t*             mcch_payload,
                      const uint8_t              mcch_payload_length)
 {
+  srsran::rwlock_write_guard lock(rwlock);
   mcch               = *mcch_;
   mch.num_mtch_sched = this->mcch.pmch_info_list[0].nof_mbms_session_info;
   for (uint32_t i = 0; i < mch.num_mtch_sched; ++i) {
@@ -1038,6 +1039,7 @@ void mac::write_mcch(const srsran::sib2_mbms_t* sib2_,
   rrc_h->add_user(SRSRAN_MRNTI, {});
 }
 
+// Internal helper function, caller must hold UE DB rwlock
 bool mac::check_ue_exists(uint16_t rnti)
 {
   if (not ue_db.contains(rnti)) {