feat(NR PHY simulators): add a SIGINT handler to some PHY simulators

When using T2 virtual functions, it is important to properly stop DPDK and free the device.
Otherwise the virtual functions may be blocked and a restart of the admin application is necessary.

Up to now, SIGINT was shutting down the PHY simulators without freeing the device.
This commit adds a signal handler to handle SIGINT in a way that allow to properly free the device.
This feature is first added to the PHY simulators that use the T2 which are `nr_ulsim`, `nr_dlsim`, `nr_ulschsim` and `nr_dlschsim`.

openair1/SIMULATION/NR_PHY/dlschsim.c

@@ -100,6 +100,10 @@ configmodule_interface_t *uniqCfg = NULL;
 
 int main(int argc, char **argv)
 {
+  stop = false;
+  __attribute__((unused)) struct sigaction oldaction;
+  sigaction(SIGINT, &sigint_action, &oldaction);
+
   int i;
   double SNR, SNR_lin, snr0 = -2.0, snr1 = 2.0;
   double snr_step = 0.1;
@@ -519,11 +523,11 @@ int main(int argc, char **argv)
 	  nr_dlsch_encoding(gNB, &msgDataTx, frame, slot, frame_parms, output, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
 	}
 
-	for (SNR = snr0; SNR < snr1; SNR += snr_step) {
+	for (SNR = snr0; SNR < snr1 && !stop; SNR += snr_step) {
 		n_errors = 0;
 		n_false_positive = 0;
 
-		for (trial = 0; trial < n_trials; trial++) {
+		for (trial = 0; trial < n_trials && !stop; trial++) {
 			for (i = 0; i < available_bits; i++) {
 #ifdef DEBUG_CODER
 				if ((i&0xf)==0)

openair1/SIMULATION/NR_PHY/dlsim.c

@@ -266,6 +266,10 @@ int NB_UE_INST = 1;
 configmodule_interface_t *uniqCfg = NULL;
 int main(int argc, char **argv)
 {
+  stop = false;
+  __attribute__((unused)) struct sigaction oldaction;
+  sigaction(SIGINT, &sigint_action, &oldaction);
+
   FILE *csv_file = NULL;
   char *filename_csv = NULL;
   setbuf(stdout, NULL);
@@ -955,7 +959,7 @@ printf("%d\n", slot);
     fprintf(csv_file,"avg_round,eff_rate,eff_throughput,TBS\n");
   }
   //---------------
-  for (SNR = snr0; SNR < snr1; SNR += .2) {
+  for (SNR = snr0; SNR < snr1 && !stop; SNR += .2) {
 
     varArray_t *table_tx=initVarArray(1000,sizeof(double));
     reset_meas(&gNB->phy_proc_tx);
@@ -985,7 +989,7 @@ printf("%d\n", slot);
     n_false_positive = 0;
     if (n_trials== 1) num_rounds = 1;
 
-    for (trial = 0; trial < n_trials; trial++) {
+    for (trial = 0; trial < n_trials && !stop; trial++) {
 
       errors_bit = 0;
       //multipath channel
@@ -1016,7 +1020,7 @@ printf("%d\n", slot);
       memset(Sched_INFO, 0, sizeof(*Sched_INFO));
       Sched_INFO->sched_response_id = -1;
 
-      while (round < num_rounds && !UE_harq_process->decodeResult) {
+      while (round < num_rounds && !UE_harq_process->decodeResult && !stop) {
         round_trials[round]++;
 
         clear_nr_nfapi_information(RC.nrmac[0], 0, frame, slot, &Sched_INFO->DL_req, &Sched_INFO->TX_req, &Sched_INFO->UL_dci_req);

openair1/SIMULATION/NR_PHY/nr_dummy_functions.c

@@ -5,6 +5,16 @@
 #include "openair1/PHY/defs_nr_UE.h"
 #include "position_interface.h"
 
+// Define signal handler to attempt graceful termination
+bool stop = false;
+
+void sigint_handler(int arg) {
+  static const char msg[] = "\nCaught SIGINT, shutting down\nPress again CTRL+C to force shutdown\n";
+  __attribute__((unused)) int unused = write(STDOUT_FILENO, msg, sizeof(msg) - 1);
+
+  stop = true;
+}
+
 int oai_nfapi_dl_tti_req(nfapi_nr_dl_tti_request_t *dl_config_req) { return (0); }
 int oai_nfapi_tx_data_req(nfapi_nr_tx_data_request_t *tx_data_req) { return (0); }
 int oai_nfapi_ul_dci_req(nfapi_nr_ul_dci_request_t *ul_dci_req) { return (0); }

openair1/SIMULATION/NR_PHY/nr_unitary_defs.h

@@ -36,6 +36,17 @@
 #include "NR_ServingCellConfigCommon.h"
 #include "NR_ServingCellConfig.h"
 
+// Define signal handler to attempt graceful termination
+extern bool stop;
+
+void sigint_handler(int arg);
+
+const struct sigaction sigint_action = {
+  .sa_handler = sigint_handler,
+  // restore handler to default upon entry to the signal handler
+  .sa_flags = SA_RESETHAND
+};
+
 int oai_exit=0;
 
 void exit_function(const char* file, const char* function, const int line, const char *s, const int assert) {

openair1/SIMULATION/NR_PHY/ulschsim.c

@@ -99,6 +99,10 @@ nrUE_params_t *get_nrUE_params(void) {
 configmodule_interface_t *uniqCfg = NULL;
 int main(int argc, char **argv)
 {
+  stop = false;
+  __attribute__((unused)) struct sigaction oldaction;
+  sigaction(SIGINT, &sigint_action, &oldaction);
+
   int i;
   double SNR, snr0 = -2.0, snr1 = 2.0, SNR_lin;
   double snr_step = 0.1;
@@ -521,11 +525,11 @@ int main(int argc, char **argv)
   ///////////
   ////////////////////////////////////////////////////////////////////
 
-  for (SNR = snr0; SNR < snr1; SNR += snr_step) {
+  for (SNR = snr0; SNR < snr1 && !stop; SNR += snr_step) {
     n_errors = 0;
     n_false_positive = 0;
 
-    for (trial = 0; trial < n_trials; trial++) {
+    for (trial = 0; trial < n_trials && !stop; trial++) {
 
       errors_bit_uncoded = 0;
 

openair1/SIMULATION/NR_PHY/ulsim.c

@@ -166,6 +166,10 @@ int NB_UE_INST = 1;
 configmodule_interface_t *uniqCfg = NULL;
 int main(int argc, char *argv[])
 {
+  stop = false;
+  __attribute__((unused)) struct sigaction oldaction;
+  sigaction(SIGINT, &sigint_action, &oldaction);
+
   FILE *csv_file = NULL;
   char *filename_csv = NULL;
   int i;
@@ -973,7 +977,7 @@ int main(int argc, char *argv[])
   //---------------
   int ret = 1;
   int srs_ret = do_SRS;
-  for (SNR = snr0; SNR <= snr1; SNR += snr_step) {
+  for (SNR = snr0; SNR <= snr1 && !stop; SNR += snr_step) {
 
     varArray_t *table_rx=initVarArray(1000,sizeof(double));
     int error_flag = 0;
@@ -1012,13 +1016,13 @@ int main(int argc, char *argv[])
     int64_t sum_srs_snr = 0;
     int srs_snr_count = 0;
 
-    for (trial = 0; trial < n_trials; trial++) {
+    for (trial = 0; trial < n_trials && !stop; trial++) {
 
       uint8_t round = 0;
       crc_status = 1;
       errors_decoding = 0;
 
-      while (round < max_rounds && crc_status) {
+      while (round < max_rounds && crc_status && !stop) {
 
         round_trials[round]++;
         rv_index = nr_get_rv(round % 4);