Reimplement itti_wait_tasks_end() to allow custom wait handlers

In the UE, we wish to handle ^C in the UE to send a message before
terminating, so we allow custom wait handlers to implement such
functionality. Use itti_wait_tasks_unblock() to unblock
itti_wait_tasks_end().

Also, implement itti_wait_tasks_end() using semaphores, as signals are
not async-signal-safe (and therefore should not be used in a signal
handler).

common/utils/ocp_itti/intertask_interface.cpp

@@ -24,6 +24,7 @@
 #include <vector>
 #include <map>
 #include <sys/eventfd.h>
+#include <semaphore.h>
 
 
 extern "C" {
@@ -434,24 +435,32 @@ extern "C" {
   void itti_send_terminate_message(task_id_t task_id) {
   }
 
-  pthread_mutex_t signal_mutex;
+  sem_t itti_sem_block;
+  void itti_wait_tasks_unblock()
+  {
+    int rc = sem_post(&itti_sem_block);
+    AssertFatal(rc == 0, "error in sem_post(): %d %s\n", errno, strerror(errno));
+  }
 
   static void catch_sigterm(int) {
     static const char msg[] = "\n** Caught SIGTERM, shutting down\n";
     __attribute__((unused))
     int unused = write(STDOUT_FILENO, msg, sizeof(msg) - 1);
-    pthread_mutex_unlock(&signal_mutex);
+    itti_wait_tasks_unblock();
   }
 
-  void itti_wait_tasks_end(void) {
+  void itti_wait_tasks_end(void (*handler)(int))
+  {
+    int rc = sem_init(&itti_sem_block, 0, 0);
+    AssertFatal(rc == 0, "error in sem_init(): %d %s\n", errno, strerror(errno));
 
-    pthread_mutex_init(&signal_mutex, NULL);
-    pthread_mutex_lock(&signal_mutex);
+    if (handler == NULL) /* no handler given: install default */
+      handler = catch_sigterm;
+    signal(SIGTERM, handler);
+    signal(SIGINT, handler);
 
-    signal(SIGTERM, catch_sigterm);
-    signal(SIGINT, catch_sigterm);
-
-    pthread_mutex_lock(&signal_mutex);
+    rc = sem_wait(&itti_sem_block);
+    AssertFatal(rc == 0, "error in sem_wait(): %d %s\n", errno, strerror(errno));
   }
 
   void itti_update_lte_time(uint32_t frame, uint8_t slot) {}