MDEV-24512 fixup: Remove after_task_callback

In commit ff5d306e we removed
dbug_after_task_callback but forgot to revert the rest of
commit bada05a8.

tpool/task.cc

-/* Copyright (C) 2019, 2020, MariaDB Corporation.
+/* Copyright (C) 2019, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute itand /or modify
 it under the terms of the GNU General Public License as published by
@@ -21,21 +21,6 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02111 - 1301 USA*/
 
 namespace tpool
 {
-
-#ifndef DBUG_OFF
-static callback_func_np after_task_callback;
-void set_after_task_callback(callback_func_np cb)
-{
-  after_task_callback= cb;
-}
-
-void execute_after_task_callback()
-{
-  if (after_task_callback)
-    after_task_callback();
-}
-#endif
-
   task::task(callback_func func, void* arg, task_group* group) :
     m_func(func), m_arg(arg), m_group(group) {}
 
@@ -50,7 +35,6 @@ void execute_after_task_callback()
     {
       /* Execute directly. */
       m_func(m_arg);
-      dbug_execute_after_task_callback();
       release();
     }
   }

tpool/task_group.cc

@@ -53,7 +53,6 @@ namespace tpool
       if (t)
       {
         t->m_func(t->m_arg);
-        dbug_execute_after_task_callback();
         t->release();
       }
       lk.lock();

tpool/tpool.h

-/* Copyright (C) 2019, 2020, MariaDB Corporation.
+/* Copyright (C) 2019, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute itand /or modify
 it under the terms of the GNU General Public License as published by
@@ -184,18 +184,6 @@ class thread_pool;
 
 extern aio *create_simulated_aio(thread_pool *tp);
 
-#ifndef DBUG_OFF
-/*
-  This function is useful for debugging to make sure all mutexes are released
-  inside a task callback
-*/
-void set_after_task_callback(callback_func_np cb);
-void execute_after_task_callback();
-#define dbug_execute_after_task_callback() execute_after_task_callback()
-#else
-#define dbug_execute_after_task_callback() do{}while(0)
-#endif
-
 class thread_pool
 {
 protected:

tpool/tpool_generic.cc

-/* Copyright (C) 2019, 2020, MariaDB Corporation.
+/* Copyright (C) 2019, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute itand /or modify
 it under the terms of the GNU General Public License as published by
@@ -311,7 +311,6 @@ class thread_pool_generic : public thread_pool
         return;
 
       m_callback(m_data);
-      dbug_execute_after_task_callback();
       m_running = false;
 
       if (m_pool && m_period)

tpool/tpool_win.cc

-/* Copyright(C) 2019 MariaDB
+/* Copyright (C) 2019, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute itand /or modify
 it under the terms of the GNU General Public License as published by
@@ -93,7 +93,6 @@ class thread_pool_win : public thread_pool
         return;
       }
       timer->m_func(timer->m_data);
-      dbug_execute_after_task_callback();
       if (timer->m_period)
         timer->set_time(timer->m_period, timer->m_period);
     }