Fix finding an empty thread state (CID 352965)

Commit a7dcf86 removed the thread
limit, but the code to locate an empty slot was broken in the process.
It would effectively allocate a new block of slots for each thread.

Signed-off-by: Erik Boasson <[email protected]>

Author: eboasson

src/core/ddsi/src/q_thread.c

@@ -284,22 +284,22 @@ static struct thread_state *grow_thread_states (void)
   return &x->thrst[0];
 }
 
-static struct thread_state *init_thread_state (const char *tname, const struct ddsi_domaingv *gv, enum thread_state_kind state)
+static struct thread_state *get_available_thread_slot ()
 {
   struct thread_states_list *cur;
-  uint32_t i = 0; // clearly, if cur != NULL, i will be initialized, but clang ain't so sure
+  uint32_t i;
   for (cur = ddsrt_atomic_ldvoidp (&thread_states.thread_states_head); cur; cur = cur->next)
     for (i = 0; i < THREAD_STATE_BATCH; i++)
       if (cur->thrst[i].state == THREAD_STATE_ZERO)
-        break;
-  struct thread_state *thrst;
-  if (cur != NULL)
-    thrst = &cur->thrst[i];
-  else
-  {
-    if ((thrst = grow_thread_states ()) == NULL)
-      return NULL;
-  }
+        return &cur->thrst[i];
+  return grow_thread_states ();
+}
+
+static struct thread_state *init_thread_state (const char *tname, const struct ddsi_domaingv *gv, enum thread_state_kind state)
+{
+  struct thread_state * const thrst = get_available_thread_slot ();
+  if (thrst == NULL)
+    return thrst;
 
   assert (vtime_asleep_p (ddsrt_atomic_ld32 (&thrst->vtime)));
   ddsrt_atomic_stvoidp (&thrst->gv, (struct ddsi_domaingv *) gv);