rrc: defer manipulations of the RLC/PDCP arrays

all calls that manipulate the RLC and/or PDCP arrays suffer
from a high deadlock risk if a PHY worker holds the RLC
AM Rx mutex at the same time when the stack wants to carry
out this reconfiguration.

this applies to RRC Reconfigs, but potentially also to RRC Connection
Reestablishment or even RRC Connection Setup, although this should
seldom be the case.

By breaking the call stack between RLC->PDCP->RRC->RCL and
carrying out the reconfig as a single task without holding the
RLC readlock the deadlock should not happen anymore.

This should fix issue #1593

srsue/src/stack/rrc/rrc.cc

@@ -905,7 +905,7 @@ bool rrc::con_reconfig(rrc_conn_recfg_s* reconfig)
           nas_sdu->N_bytes = reconfig_r8->ded_info_nas_list[i].size();
           nas->write_pdu(RB_ID_SRB1, std::move(nas_sdu));
         } else {
-          rrc_log->error("Fatal Error: Couldn't allocate PDU in handle_rrc_con_reconfig().\n");
+          rrc_log->error("Fatal Error: Couldn't allocate PDU in %s.\n", __FUNCTION__);
           return;
         }
       }
@@ -946,14 +946,18 @@ void rrc::handle_rrc_con_reconfig(uint32_t lcid, rrc_conn_recfg_s* reconfig)
   previous_phy_cfg = current_phy_cfg;
   previous_mac_cfg = current_mac_cfg;
 
-  rrc_conn_recfg_r8_ies_s* reconfig_r8 = &reconfig->crit_exts.c1().rrc_conn_recfg_r8();
+  // Execute in next iteration to break RLC/PDCP call stack
-  if (reconfig_r8->mob_ctrl_info_present) {
+  rrc_conn_recfg_s reconfig_ = *reconfig;
-    con_reconfig_ho(reconfig);
+  task_sched.defer_task([this, reconfig_]() mutable {
-  } else {
+    rrc_conn_recfg_r8_ies_s* reconfig_r8 = &reconfig_.crit_exts.c1().rrc_conn_recfg_r8();
-    if (!con_reconfig(reconfig)) {
+    if (reconfig_r8->mob_ctrl_info_present) {
-      con_reconfig_failed();
+      con_reconfig_ho(&reconfig_);
+    } else {
+      if (!con_reconfig(&reconfig_)) {
+        con_reconfig_failed();
+      }
     }
-  }
+  });
 }
 
 /* Actions upon reception of RRCConnectionRelease 5.3.8.3 */
@@ -2220,48 +2224,57 @@ void rrc::apply_scell_config(rrc_conn_recfg_r8_ies_s* reconfig_r8)
 
 void rrc::handle_con_setup(rrc_conn_setup_s* setup)
 {
-  // Must enter CONNECT before stopping T300
+  // Execute in next iteration to break RLC/PDCP call stack
-  state = RRC_STATE_CONNECTED;
+  rrc_conn_setup_s setup_ = *setup;
-  t300.stop();
+  task_sched.defer_task([this, setup_]() mutable {
-  t302.stop();
+    // Must enter CONNECT before stopping T300
-  rrc_log->console("RRC Connected\n");
+    state = RRC_STATE_CONNECTED;
+    t300.stop();
+    t302.stop();
+    rrc_log->console("RRC Connected\n");
 
-  // Apply the Radio Resource configuration
+    // Apply the Radio Resource configuration
-  apply_rr_config_dedicated(&setup->crit_exts.c1().rrc_conn_setup_r8().rr_cfg_ded);
+    apply_rr_config_dedicated(&setup_.crit_exts.c1().rrc_conn_setup_r8().rr_cfg_ded);
 
-  nas->set_barring(srslte::barring_t::none);
+    nas->set_barring(srslte::barring_t::none);
 
-  if (dedicated_info_nas.get()) {
+    if (dedicated_info_nas.get()) {
-    send_con_setup_complete(std::move(dedicated_info_nas));
+      send_con_setup_complete(std::move(dedicated_info_nas));
-  } else {
+    } else {
-    rrc_log->error("Pending to transmit a ConnectionSetupComplete but no dedicatedInfoNAS was in queue\n");
+      rrc_log->error("Pending to transmit a ConnectionSetupComplete but no dedicatedInfoNAS was in queue\n");
-  }
+    }
+  });
 }
 
 /* Reception of RRCConnectionReestablishment by the UE 5.3.7.5 */
-void rrc::handle_con_reest(rrc_conn_reest_s* setup)
+void rrc::handle_con_reest(rrc_conn_reest_s* reest)
 {
-  t301.stop();
+  // Execute in next iteration to break RLC/PDCP call stack
+  rrc_conn_reest_s reest_ = *reest;
+  task_sched.defer_task([this, reest_]() mutable {
+    t301.stop();
 
-  // Reestablish PDCP and RLC for SRB1
+    // Reestablish PDCP and RLC for SRB1
-  pdcp->reestablish(1);
+    pdcp->reestablish(1);
-  rlc->reestablish(1);
+    rlc->reestablish(1);
 
-  // Update RRC Integrity keys
+    // Update RRC Integrity keys
-  int ncc = setup->crit_exts.c1().rrc_conn_reest_r8().next_hop_chaining_count;
+    int ncc = reest_.crit_exts.c1().rrc_conn_reest_r8().next_hop_chaining_count;
-  usim->generate_as_keys_ho(meas_cells.serving_cell().get_pci(), meas_cells.serving_cell().get_earfcn(), ncc, &sec_cfg);
+    usim->generate_as_keys_ho(
-  pdcp->config_security_all(sec_cfg);
+        meas_cells.serving_cell().get_pci(), meas_cells.serving_cell().get_earfcn(), ncc, &sec_cfg);
+    pdcp->config_security_all(sec_cfg);
 
-  // Apply the Radio Resource configuration
+    // Apply the Radio Resource configuration
-  apply_rr_config_dedicated(&setup->crit_exts.c1().rrc_conn_reest_r8().rr_cfg_ded);
+    apply_rr_config_dedicated(&reest_.crit_exts.c1().rrc_conn_reest_r8().rr_cfg_ded);
 
-  // Resume SRB1
+    // Resume SRB1
-  rlc->resume_bearer(1);
+    rlc->resume_bearer(1);
 
-  // Send ConnectionSetupComplete message
+    // Send ConnectionSetupComplete message
-  send_con_restablish_complete();
+    send_con_restablish_complete();
 
-  reestablishment_successful = true;
+    reestablishment_successful = true;
+  });
 }
 
 void rrc::add_srb(srb_to_add_mod_s* srb_cnfg)