threading: explain purpose of threadvars mucond

src/counters.c

@@ -306,6 +306,8 @@ static void *SCPerfMgmtThread(void *arg)
         cond_time.tv_sec = time(NULL) + sc_counter_tts;
         cond_time.tv_nsec = 0;
 
+        /* wait for the set time, or until we are woken up by
+         * the shutdown procedure */
         SCCtrlMutexLock(tv_local->ctrl_mutex);
         SCCtrlCondTimedwait(tv_local->ctrl_cond, tv_local->ctrl_mutex, &cond_time);
         SCCtrlMutexUnlock(tv_local->ctrl_mutex);
@@ -380,6 +382,8 @@ static void *SCPerfWakeupThread(void *arg)
         cond_time.tv_sec = time(NULL) + SC_PERF_WUT_TTS;
         cond_time.tv_nsec = 0;
 
+        /* wait for the set time, or until we are woken up by
+         * the shutdown procedure */
         SCCtrlMutexLock(tv_local->ctrl_mutex);
         SCCtrlCondTimedwait(tv_local->ctrl_cond, tv_local->ctrl_mutex, &cond_time);
         SCCtrlMutexUnlock(tv_local->ctrl_mutex);
@@ -828,6 +832,9 @@ void SCPerfInitCounterApi(void)
 /**
  * \brief Spawns the wakeup, and the management thread used by the perf
  *        counter api
+ *
+ *  The threads use the condition variable in the thread vars to control
+ *  their wait loops to make sure the main thread can quickly kill them.
  */
 void SCPerfSpawnThreads(void)
 {

src/tm-threads.c

@@ -1748,6 +1748,9 @@ void TmThreadSetAOF(ThreadVars *tv, uint8_t aof)
 /**
  * \brief Initializes the mutex and condition variables for this TV
  *
+ * It can be used by a thread to control a wait loop that can also be
+ * influenced by other threads.
+ *
  * \param tv Pointer to a TV instance
  */
 void TmThreadInitMC(ThreadVars *tv)
@@ -1760,19 +1763,19 @@ void TmThreadInitMC(ThreadVars *tv)
 
     if (SCCtrlMutexInit(tv->ctrl_mutex, NULL) != 0) {
         printf("Error initializing the tv->m mutex\n");
-        exit(0);
+        exit(EXIT_FAILURE);
     }
 
     if ( (tv->ctrl_cond = SCMalloc(sizeof(*tv->ctrl_cond))) == NULL) {
         SCLogError(SC_ERR_FATAL, "Fatal error encountered in TmThreadInitMC.  "
                    "Exiting...");
-        exit(0);
+        exit(EXIT_FAILURE);
     }
 
     if (SCCtrlCondInit(tv->ctrl_cond, NULL) != 0) {
         SCLogError(SC_ERR_FATAL, "Error initializing the tv->cond condition "
                    "variable");
-        exit(0);
+        exit(EXIT_FAILURE);
     }
 
     return;