smp: Fix scheduler helping protocol

Ensure that scheduler nodes in the SCHEDULER_HELP_ACTIVE_OWNER or
SCHEDULER_HELP_ACTIVE_RIVAL helping state are always
SCHEDULER_SMP_NODE_READY or SCHEDULER_SMP_NODE_SCHEDULED to ensure the
MrsP protocol properties.

3 files changed, 283 insertions, 66 deletions

diff --git a/cpukit/score/include/rtems/score/schedulerimpl.h b/cpukit/score/include/rtems/score/schedulerimpl.h
index b262b91f84..31ae6d184d 100644
--- a/cpukit/score/include/rtems/score/schedulerimpl.h
+++ b/cpukit/score/include/rtems/score/schedulerimpl.h
@@ -949,9 +949,10 @@ void _Scheduler_Thread_change_resource_root(
 /**
  * @brief Use an idle thread for this scheduler node.
  *
- * A thread in the SCHEDULER_HELP_ACTIVE_OWNER owner state may use an idle
- * thread for the scheduler node owned by itself in case it executes currently
- * using another scheduler node or in case it is in a blocking state.
+ * A thread in the SCHEDULER_HELP_ACTIVE_OWNER or SCHEDULER_HELP_ACTIVE_RIVAL
+ * helping state may use an idle thread for the scheduler node owned by itself
+ * in case it executes currently using another scheduler node or in case it is
+ * in a blocking state.
  *
  * @param[in] context The scheduler instance context.
  * @param[in] node The node which wants to use the idle thread.
@@ -965,7 +966,10 @@ RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Use_idle_thread(
 {
   Thread_Control *idle = ( *get_idle_thread )( context );
 
-  _Assert( node->help_state == SCHEDULER_HELP_ACTIVE_OWNER );
+  _Assert(
+    node->help_state == SCHEDULER_HELP_ACTIVE_OWNER
+      || node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL
+  );
   _Assert( _Scheduler_Node_get_idle( node ) == NULL );
   _Assert(
     _Scheduler_Node_get_owner( node ) == _Scheduler_Node_get_user( node )
@@ -1009,6 +1013,8 @@ RTEMS_INLINE_ROUTINE bool _Scheduler_Try_to_schedule_node(
   if ( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL) {
     if ( user->Scheduler.state == THREAD_SCHEDULER_READY ) {
       _Scheduler_Thread_set_scheduler_and_node( user, node, owner );
+    } else if ( owner->Scheduler.state == THREAD_SCHEDULER_BLOCKED ) {
+      _Scheduler_Use_idle_thread( context, node, get_idle_thread );
     } else {
       _Scheduler_Node_set_user( node, owner );
     }
@@ -1072,6 +1078,9 @@ RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Release_idle_thread(
  * @brief Block this scheduler node.
  *
  * @param[in] context The scheduler instance context.
+ * @param[in] thread The thread which wants to get blocked referencing this
+ *   node.  This is not necessarily the user of this node in case the node
+ *   participates in the scheduler helping protocol.
  * @param[in] node The node which wants to get blocked.
  * @param[in] is_scheduled This node is scheduled.
  * @param[in] get_idle_thread Function to get an idle thread.
@@ -1087,23 +1096,46 @@ RTEMS_INLINE_ROUTINE bool _Scheduler_Block_node(
   Scheduler_Get_idle_thread  get_idle_thread
 )
 {
-  bool block;
-  Thread_Control *old_user = _Scheduler_Node_get_user( node );
-  Thread_Control *new_user = NULL;
+  Thread_Control *old_user;
+  Thread_Control *new_user;
 
-  _Scheduler_Thread_change_state( old_user, THREAD_SCHEDULER_BLOCKED );
+  _Scheduler_Thread_change_state( thread, THREAD_SCHEDULER_BLOCKED );
 
-  if ( is_scheduled ) {
-    if ( node->help_state == SCHEDULER_HELP_ACTIVE_OWNER ) {
+  if ( node->help_state == SCHEDULER_HELP_YOURSELF ) {
+    _Assert( thread == _Scheduler_Node_get_user( node ) );
+
+    return true;
+  }
+
+  new_user = NULL;
+
+  if ( node->help_state == SCHEDULER_HELP_ACTIVE_OWNER ) {
+    if ( is_scheduled ) {
+      _Assert( thread == _Scheduler_Node_get_user( node ) );
+      old_user = thread;
       new_user = _Scheduler_Use_idle_thread( context, node, get_idle_thread );
-    } else if ( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL ) {
-      Thread_Control *owner = _Scheduler_Node_get_owner( node );
+    }
+  } else if ( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL ) {
+    if ( is_scheduled ) {
+      old_user = _Scheduler_Node_get_user( node );
 
-      if ( thread == old_user && owner != old_user ) {
-        new_user = owner;
-        _Scheduler_Node_set_user( node, new_user );
+      if ( thread == old_user ) {
+        Thread_Control *owner = _Scheduler_Node_get_owner( node );
+
+        if (
+          thread != owner
+            && owner->Scheduler.state == THREAD_SCHEDULER_READY
+        ) {
+          new_user = owner;
+          _Scheduler_Node_set_user( node, new_user );
+        } else {
+          new_user = _Scheduler_Use_idle_thread( context, node, get_idle_thread );
+        }
       }
     }
+  } else {
+    /* Not implemented, this is part of the OMIP support path. */
+    _Assert(0);
   }
 
   if ( new_user != NULL ) {
@@ -1112,13 +1144,9 @@ RTEMS_INLINE_ROUTINE bool _Scheduler_Block_node(
     _Scheduler_Thread_change_state( new_user, THREAD_SCHEDULER_SCHEDULED );
     _Thread_Set_CPU( new_user, cpu );
     _Thread_Dispatch_update_heir( _Per_CPU_Get(), cpu, new_user );
-
-    block = false;
-  } else {
-    block = true;
   }
 
-  return block;
+  return false;
 }
 
 /**
@@ -1146,26 +1174,38 @@ RTEMS_INLINE_ROUTINE bool _Scheduler_Unblock_node(
   if ( is_scheduled ) {
     Thread_Control *old_user = _Scheduler_Node_get_user( node );
     Per_CPU_Control *cpu = _Thread_Get_CPU( old_user );
+    Thread_Control *idle = _Scheduler_Release_idle_thread(
+      context,
+      node,
+      release_idle_thread
+    );
+    Thread_Control *owner = _Scheduler_Node_get_owner( node );
+    Thread_Control *new_user;
 
     if ( node->help_state == SCHEDULER_HELP_ACTIVE_OWNER ) {
-      Thread_Control *idle = _Scheduler_Release_idle_thread(
-        context,
-        node,
-        release_idle_thread
-      );
-
       _Assert( idle != NULL );
-      (void) idle;
+      new_user = the_thread;
+    } else if ( idle != NULL ) {
+      _Assert( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL );
+      new_user = the_thread;
+    } else if ( the_thread != owner ) {
+      _Assert( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL );
+      _Assert( old_user != the_thread );
+      _Scheduler_Thread_change_state( owner, THREAD_SCHEDULER_READY );
+      new_user = the_thread;
+      _Scheduler_Node_set_user( node, new_user );
     } else {
       _Assert( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL );
-
-      _Scheduler_Thread_change_state( old_user, THREAD_SCHEDULER_READY );
-      _Scheduler_Node_set_user( node, the_thread );
+      _Assert( old_user != the_thread );
+      _Scheduler_Thread_change_state( the_thread, THREAD_SCHEDULER_READY );
+      new_user = NULL;
     }
 
-    _Scheduler_Thread_change_state( the_thread, THREAD_SCHEDULER_SCHEDULED );
-    _Thread_Set_CPU( the_thread, cpu );
-    _Thread_Dispatch_update_heir( _Per_CPU_Get(), cpu, the_thread );
+    if ( new_user != NULL ) {
+      _Scheduler_Thread_change_state( new_user, THREAD_SCHEDULER_SCHEDULED );
+      _Thread_Set_CPU( new_user, cpu );
+      _Thread_Dispatch_update_heir( _Per_CPU_Get(), cpu, new_user );
+    }
 
     unblock = false;
   } else {
@@ -1243,7 +1283,10 @@ RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Ask_scheduled_node_for_help(
     if ( needs_help->Scheduler.state == THREAD_SCHEDULER_READY ) {
       new_user = needs_help;
     } else {
-      _Assert( node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL );
+      _Assert(
+        node->help_state == SCHEDULER_HELP_ACTIVE_OWNER
+          || node->help_state == SCHEDULER_HELP_ACTIVE_RIVAL
+      );
       _Assert( offers_help->Scheduler.node == offers_help->Scheduler.own_node );
 
       new_user = offers_help;
diff --git a/testsuites/smptests/smpmrsp01/init.c b/testsuites/smptests/smpmrsp01/init.c
index b6727288cd..acda13fd1c 100644
--- a/testsuites/smptests/smpmrsp01/init.c
+++ b/testsuites/smptests/smpmrsp01/init.c
@@ -54,7 +54,8 @@ typedef struct {
 typedef struct {
   rtems_id main_task_id;
   rtems_id migration_task_id;
-  rtems_id high_task_id;
+  rtems_id low_task_id[2];
+  rtems_id high_task_id[2];
   rtems_id timer_id;
   rtems_id counting_sem_id;
   rtems_id mrsp_ids[MRSP_COUNT];
@@ -68,7 +69,8 @@ typedef struct {
   SMP_lock_Control switch_lock;
   size_t switch_index;
   switch_event switch_events[32];
-  volatile bool run;
+  volatile bool high_run[2];
+  volatile bool low_run[2];
 } test_context;
 
 static test_context test_instance = {
@@ -717,9 +719,6 @@ static void test_mrsp_multiple_obtain(void)
 
   sc = rtems_semaphore_delete(sem_c_id);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
-
-  change_prio(RTEMS_SELF, 2);
-  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 }
 
 static void run_task(rtems_task_argument arg)
@@ -753,8 +752,9 @@ static void ready_unlock_worker(rtems_task_argument arg)
   /* Done (G) */
   barrier(ctx, &barrier_state);
 
-  rtems_task_suspend(RTEMS_SELF);
-  rtems_test_assert(0);
+  while (true) {
+    /* Do nothing */
+  }
 }
 
 static void unblock_ready_timer(rtems_id timer_id, void *arg)
@@ -763,16 +763,16 @@ static void unblock_ready_timer(rtems_id timer_id, void *arg)
   rtems_status_code sc;
 
   sc = rtems_task_start(
-    ctx->high_task_id,
+    ctx->high_task_id[0],
     run_task,
-    (rtems_task_argument) &ctx->run
+    (rtems_task_argument) &ctx->high_run[0]
   );
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_suspend(ctx->high_task_id);
+  sc = rtems_task_suspend(ctx->high_task_id[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_resume(ctx->high_task_id);
+  sc = rtems_task_resume(ctx->high_task_id[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
   /*
@@ -783,7 +783,7 @@ static void unblock_ready_timer(rtems_id timer_id, void *arg)
   sc = rtems_event_transient_send(ctx->main_task_id);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_suspend(ctx->high_task_id);
+  sc = rtems_task_suspend(ctx->high_task_id[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 }
 
@@ -802,16 +802,37 @@ static void unblock_ready_owner(test_context *ctx)
   sc = rtems_event_transient_receive(RTEMS_WAIT, RTEMS_NO_TIMEOUT);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  rtems_test_assert(!ctx->run);
+  rtems_test_assert(!ctx->high_run[0]);
 }
 
-static void unblock_ready_rival(test_context *ctx)
+static void unblock_owner_before_rival_timer(rtems_id timer_id, void *arg)
 {
+  test_context *ctx = arg;
   rtems_status_code sc;
-  SMP_barrier_State barrier_state = SMP_BARRIER_STATE_INITIALIZER;
 
-  sc = rtems_task_start(ctx->worker_ids[0], ready_unlock_worker, 0);
+  sc = rtems_task_suspend(ctx->high_task_id[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_suspend(ctx->high_task_id[1]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+}
+
+static void unblock_owner_after_rival_timer(rtems_id timer_id, void *arg)
+{
+  test_context *ctx = arg;
+  rtems_status_code sc;
+
+  sc = rtems_task_suspend(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_suspend(ctx->high_task_id[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+}
+
+static void various_block_unblock(test_context *ctx)
+{
+  rtems_status_code sc;
+  SMP_barrier_State barrier_state = SMP_BARRIER_STATE_INITIALIZER;
 
   /* Worker obtain (F) */
   barrier(ctx, &barrier_state);
@@ -822,41 +843,143 @@ static void unblock_ready_rival(test_context *ctx)
   sc = rtems_task_suspend(ctx->worker_ids[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_set_scheduler(ctx->high_task_id, ctx->scheduler_ids[1]);
+  sc = rtems_task_wake_after(2);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_resume(ctx->high_task_id);
+  sc = rtems_task_start(
+    ctx->high_task_id[1],
+    run_task,
+    (rtems_task_argument) &ctx->high_run[1]
+  );
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  while (!ctx->run) {
+  while (!ctx->high_run[1]) {
     /* Do noting */
   }
 
   sc = rtems_task_resume(ctx->worker_ids[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_suspend(ctx->high_task_id);
+  /* Try to schedule a blocked active rival */
+
+  sc = rtems_task_suspend(ctx->worker_ids[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_suspend(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_resume(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_resume(ctx->worker_ids[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  rtems_test_assert(rtems_get_current_processor() == 0);
+
+  /* Use node of the active rival */
+
+  sc = rtems_task_suspend(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_resume(ctx->high_task_id[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  rtems_test_assert(rtems_get_current_processor() == 1);
+
+  sc = rtems_task_suspend(ctx->worker_ids[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_resume(ctx->worker_ids[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  /*
+   * Try to schedule an active rival with an already scheduled active owner
+   * user.
+   */
+
+  sc = rtems_timer_fire_after(
+    ctx->timer_id,
+    2,
+    unblock_owner_before_rival_timer,
+    ctx
+  );
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  /* This will take the processor away from us, the timer will help later */
+  sc = rtems_task_resume(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  /*
+   * Try to schedule an active owner with an already scheduled active rival
+   * user.
+   */
+
+  sc = rtems_task_resume(ctx->high_task_id[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_timer_fire_after(
+    ctx->timer_id,
+    2,
+    unblock_owner_after_rival_timer,
+    ctx
+  );
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  /* This will take the processor away from us, the timer will help later */
+  sc = rtems_task_resume(ctx->high_task_id[1]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
   sc = rtems_semaphore_release(ctx->mrsp_ids[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
+  rtems_test_assert(rtems_get_current_processor() == 0);
+
   assert_prio(RTEMS_SELF, 4);
 
-  /* Worker done (F) */
+  /* Worker done (G) */
   barrier(ctx, &barrier_state);
 }
 
-static void test_mrsp_unblock_ready(test_context *ctx)
+static void start_low_task(test_context *ctx, size_t i)
 {
   rtems_status_code sc;
 
-  puts("test MrsP unblock ready");
+  sc = rtems_task_create(
+    rtems_build_name('L', 'O', 'W', '0' + i),
+    5,
+    RTEMS_MINIMUM_STACK_SIZE,
+    RTEMS_DEFAULT_MODES,
+    RTEMS_DEFAULT_ATTRIBUTES,
+    &ctx->low_task_id[i]
+  );
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_set_scheduler(ctx->low_task_id[i], ctx->scheduler_ids[i]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_start(
+    ctx->low_task_id[i],
+    run_task,
+    (rtems_task_argument) &ctx->low_run[i]
+  );
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+}
+
+static void test_mrsp_various_block_and_unblock(test_context *ctx)
+{
+  rtems_status_code sc;
 
-  ctx->run = false;
+  puts("test MrsP various block and unblock");
 
   change_prio(RTEMS_SELF, 4);
 
+  reset_switch_events(ctx);
+
+  ctx->low_run[0] = false;
+  ctx->low_run[1] = false;
+  ctx->high_run[0] = false;
+  ctx->high_run[1] = false;
+
   sc = rtems_semaphore_create(
     rtems_build_name(' ', ' ', ' ', 'A'),
     1,
@@ -870,16 +993,29 @@ static void test_mrsp_unblock_ready(test_context *ctx)
   assert_prio(RTEMS_SELF, 4);
 
   sc = rtems_task_create(
-    rtems_build_name('H', 'I', 'G', 'H'),
+    rtems_build_name('H', 'I', 'G', '0'),
     2,
     RTEMS_MINIMUM_STACK_SIZE,
     RTEMS_DEFAULT_MODES,
     RTEMS_DEFAULT_ATTRIBUTES,
-    &ctx->high_task_id
+    &ctx->high_task_id[0]
   );
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
   sc = rtems_task_create(
+    rtems_build_name('H', 'I', 'G', '1'),
+    2,
+    RTEMS_MINIMUM_STACK_SIZE,
+    RTEMS_DEFAULT_MODES,
+    RTEMS_DEFAULT_ATTRIBUTES,
+    &ctx->high_task_id[1]
+  );
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_set_scheduler(ctx->high_task_id[1], ctx->scheduler_ids[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_create(
     rtems_build_name('W', 'O', 'R', 'K'),
     4,
     RTEMS_MINIMUM_STACK_SIZE,
@@ -892,28 +1028,46 @@ static void test_mrsp_unblock_ready(test_context *ctx)
   sc = rtems_task_set_scheduler(ctx->worker_ids[0], ctx->scheduler_ids[1]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
+  sc = rtems_task_start(ctx->worker_ids[0], ready_unlock_worker, 0);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
   sc = rtems_timer_create(
     rtems_build_name('T', 'I', 'M', 'R'),
     &ctx->timer_id
   );
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
+  /* In case these tasks run, then we have a MrsP protocol violation */
+  start_low_task(ctx, 0);
+  start_low_task(ctx, 1);
+
   unblock_ready_owner(ctx);
-  unblock_ready_rival(ctx);
+  various_block_unblock(ctx);
+
+  rtems_test_assert(!ctx->low_run[0]);
+  rtems_test_assert(!ctx->low_run[1]);
+
+  print_switch_events(ctx);
 
   sc = rtems_timer_delete(ctx->timer_id);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
+  sc = rtems_task_delete(ctx->high_task_id[0]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
+  sc = rtems_task_delete(ctx->high_task_id[1]);
+  rtems_test_assert(sc == RTEMS_SUCCESSFUL);
+
   sc = rtems_task_delete(ctx->worker_ids[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_task_delete(ctx->high_task_id);
+  sc = rtems_task_delete(ctx->low_task_id[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  sc = rtems_semaphore_delete(ctx->mrsp_ids[0]);
+  sc = rtems_task_delete(ctx->low_task_id[1]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 
-  change_prio(RTEMS_SELF, 2);
+  sc = rtems_semaphore_delete(ctx->mrsp_ids[0]);
   rtems_test_assert(sc == RTEMS_SUCCESSFUL);
 }
 
@@ -1421,7 +1575,7 @@ static void Init(rtems_task_argument arg)
   test_mrsp_unlock_order_error();
   test_mrsp_deadlock_error(ctx);
   test_mrsp_multiple_obtain();
-  test_mrsp_unblock_ready(ctx);
+  test_mrsp_various_block_and_unblock(ctx);
   test_mrsp_obtain_and_sleep_and_release(ctx);
   test_mrsp_obtain_and_release_with_help(ctx);
   test_mrsp_obtain_and_release(ctx);
diff --git a/testsuites/smptests/smpmrsp01/smpmrsp01.scn b/testsuites/smptests/smpmrsp01/smpmrsp01.scn
index a32d71f402..1fc8b6b577 100644
--- a/testsuites/smptests/smpmrsp01/smpmrsp01.scn
+++ b/testsuites/smptests/smpmrsp01/smpmrsp01.scn
@@ -5,7 +5,27 @@ test MrsP nested obtain error
 test MrsP unlock order error
 test MrsP deadlock error
 test MrsP multiple obtain
-test MrsP unblock ready
+test MrsP various block and unblock
+[1] IDLE -> WORK (prio   4, node WORK)
+[0] MAIN -> IDLE (prio   3, node MAIN)
+[0] IDLE -> MAIN (prio   3, node MAIN)
+[1] WORK -> IDLE (prio   3, node WORK)
+[1] IDLE -> HIG1 (prio   2, node HIG1)
+[1] HIG1 -> IDLE (prio   3, node WORK)
+[1] IDLE -> HIG1 (prio   2, node HIG1)
+[1] HIG1 -> WORK (prio   3, node WORK)
+[1] WORK -> MAIN (prio   3, node WORK)
+[0] MAIN -> HIG0 (prio   2, node HIG0)
+[1] MAIN -> HIG1 (prio   2, node HIG1)
+[1] HIG1 -> WORK (prio   3, node WORK)
+[0] HIG0 -> MAIN (prio   3, node MAIN)
+[1] WORK -> MAIN (prio   3, node WORK)
+[0] MAIN -> HIG0 (prio   2, node HIG0)
+[1] MAIN -> HIG1 (prio   2, node HIG1)
+[1] HIG1 -> MAIN (prio   3, node WORK)
+[0] HIG0 -> IDLE (prio   4, node MAIN)
+[1] MAIN -> WORK (prio   3, node WORK)
+[0] IDLE -> MAIN (prio   4, node MAIN)
 test MrsP obtain and sleep and release
 [0] MAIN ->  RUN (prio   2, node  RUN)
 [0]  RUN -> MAIN (prio   1, node MAIN)