Avoid control threads race condition

src/control/control.c

@@ -203,6 +203,7 @@ void dt_control_init(const gboolean withgui)
   s->input_drivers = NULL;
   dt_atomic_set_int(&s->quitting, 0);
   dt_atomic_set_int(&s->pending_jobs, 0);
+  dt_atomic_set_int(&s->running_jobs, 0);
   s->cups_started = FALSE;
 
   dt_action_define_fallback(DT_ACTION_TYPE_IOP, &dt_action_def_iop);

src/control/control.h

@@ -181,6 +181,7 @@ typedef struct dt_control_t
   dt_atomic_int running;
   dt_atomic_int quitting;
   dt_atomic_int pending_jobs;
+  dt_atomic_int running_jobs;
   gboolean cups_started;
   gboolean export_scheduled;
   dt_pthread_mutex_t queue_mutex, cond_mutex;

src/control/jobs.c

@@ -516,6 +516,7 @@ static void *_control_work_res(void *ptr)
   dt_pthread_setname(name);
   free(params);
   const int32_t threadid_res = _control_get_threadid_res();
+  dt_atomic_add_int(&s->running_jobs, 1);
   while(dt_control_running())
   {
     // dt_print(DT_DEBUG_CONTROL, "[control_work] %d", threadid_res);
@@ -538,6 +539,7 @@ static void *_control_worker_kicker(void *ptr)
 {
   dt_control_t *control = (dt_control_t *)ptr;
   dt_pthread_setname("kicker");
+  dt_atomic_add_int(&control->running_jobs, 1);
   while(dt_control_running())
   {
     sleep(2);
@@ -561,6 +563,7 @@ static void *_control_work(void *ptr)
   dt_pthread_setname(name);
   free(params);
 
+  dt_atomic_add_int(&control->running_jobs, 1);
   while(dt_control_running())
   {
     if(_control_run_job(control))
@@ -645,8 +648,40 @@ void dt_control_jobs_init()
 #ifdef HAVE_GPHOTO2
   err |= dt_pthread_create(&control->update_gphoto_thread, dt_update_cameras_thread, control);
 #endif
+
   if(err != 0)
-    dt_print(DT_DEBUG_ALWAYS, "[dt_control_jobs_init] couldn't create all threads, problems ahead");
+  {
+    /* FIXME can we handle this better?
+        Should we unset control->running here? requires further investigation
+        on how to join or avoid rogue threads
+    */
+    dt_print(DT_DEBUG_ALWAYS, "[dt_control_jobs_init] ERROR STARTING THREADS, PROBLEMS AHEAD");
+  }
+  else // no errors reported so we test & wait
+  {
+    const int requested = control->num_threads + 1 + DT_CTL_WORKER_RESERVED;
+    int running = 0;
+    for(int i = 0; i < 1000; i++)
+    {
+      running = dt_atomic_get_int(&control->running_jobs);
+      dt_print(DT_DEBUG_CONTROL, "[dt_control_jobs_init] %d of %d threads running", running, requested);
+      if(running == requested) break;
+      g_usleep(1000);   // let's wait for up to 1sec for OS dispatching the pthreads
+    }
+    if(running != requested)
+      dt_print(DT_DEBUG_ALWAYS, "[dt_control_jobs_init] ERROR STARTED %d THREADS of %d, PROBLEMS AHEAD",
+        running, requested);
+  }
+}
+
+gboolean dt_control_all_running()
+{
+  if(!dt_control_running())
+    return FALSE;
+
+  dt_control_t *control = darktable.control;
+  const int requested = control->num_threads + 1 + DT_CTL_WORKER_RESERVED;
+  return dt_atomic_get_int(&control->running_jobs) == requested;
 }
 
 void dt_control_jobs_cleanup()

src/control/jobs.h

@@ -82,6 +82,7 @@ double dt_control_job_get_progress(const dt_job_t *job);
 void dt_control_jobs_init(void);
 void dt_control_jobs_cleanup(void);
 int dt_control_jobs_pending(void);
+gboolean dt_control_all_running(void);
 
 gboolean dt_control_add_job(dt_job_queue_t queue_id, dt_job_t *job);
 gboolean dt_control_add_job_res(dt_job_t *job, const int32_t res);

src/gui/gtk.c

@@ -1622,7 +1622,7 @@ void dt_gui_gtk_run(dt_gui_gtk_t *gui)
   dt_osx_focus_window();
 #endif
   /* start the event loop */
-  if(dt_control_running())
+  if(dt_control_all_running())
   {
     g_atomic_int_set(&darktable.gui_running, 1);
     gtk_main();