score: Rework idle handling in SMP schedulers

This patch fixes an issue with the idle thread handling in the SMP
scheduler framework used for the MrsP locking protocol.  The approach to
use a simple chain of unused idle threads is broken for schedulers which
support thread to processor affinity.  The reason is that the thread to
processor affinity introduces another ordering indicator which may under
certain conditions lead to a reordering of idle threads in the scheduled
chain.  This reordering is not propagated to the chain of unused idle
threads.  This could lead to use an idle thread for a sticky scheduler
node which is already in use.  This locks up the system in infinite
loops in the thread context switch procedure.

To fix this, the SMP scheduler implementations must now provide
callbacks to get and release an unused idle thread.

Update #4531.

1 files changed, 54 insertions, 11 deletions

diff --git a/cpukit/score/src/scheduleredfsmp.c b/cpukit/score/src/scheduleredfsmp.c
index 0b0ee6ed21..28266dd13d 100644
--- a/cpukit/score/src/scheduleredfsmp.c
+++ b/cpukit/score/src/scheduleredfsmp.c
@@ -409,10 +409,36 @@ static inline void _Scheduler_EDF_SMP_Move_from_ready_to_scheduled(
   );
 }
 
+static inline Scheduler_Node *_Scheduler_EDF_SMP_Get_idle( void *arg )
+{
+  Scheduler_EDF_SMP_Context *self;
+  Scheduler_Node            *lowest_ready;
+
+  self = _Scheduler_EDF_SMP_Get_self( arg );
+  lowest_ready = (Scheduler_Node *) _RBTree_Maximum( &self->Ready[ 0 ].Queue );
+  _Assert( lowest_ready != NULL );
+  _RBTree_Extract( &self->Ready[ 0 ].Queue, &lowest_ready->Node.RBTree );
+  _Chain_Initialize_node( &lowest_ready->Node.Chain );
+
+  return lowest_ready;
+}
+
+static inline void _Scheduler_EDF_SMP_Release_idle(
+  Scheduler_Node *node,
+  void           *arg
+)
+{
+  Scheduler_EDF_SMP_Context *self;
+
+  self = _Scheduler_EDF_SMP_Get_self( arg );
+  _RBTree_Initialize_node( &node->Node.RBTree );
+  _RBTree_Append( &self->Ready[ 0 ].Queue, &node->Node.RBTree );
+}
+
 static inline void _Scheduler_EDF_SMP_Allocate_processor(
   Scheduler_Context *context,
   Scheduler_Node    *scheduled_base,
-  Scheduler_Node    *victim_base,
+  Thread_Control    *victim_thread,
   Per_CPU_Control   *victim_cpu
 )
 {
@@ -420,7 +446,7 @@ static inline void _Scheduler_EDF_SMP_Allocate_processor(
   Scheduler_EDF_SMP_Node        *scheduled;
   uint8_t                        rqi;
 
-  (void) victim_base;
+  (void) victim_thread;
   self = _Scheduler_EDF_SMP_Get_self( context );
   scheduled = _Scheduler_EDF_SMP_Node_downcast( scheduled_base );
   rqi = scheduled->ready_queue_index;
@@ -471,7 +497,9 @@ void _Scheduler_EDF_SMP_Block(
     _Scheduler_EDF_SMP_Extract_from_ready,
     _Scheduler_EDF_SMP_Get_highest_ready,
     _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -489,8 +517,11 @@ static inline bool _Scheduler_EDF_SMP_Enqueue(
     _Scheduler_EDF_SMP_Insert_ready,
     _Scheduler_EDF_SMP_Insert_scheduled,
     _Scheduler_EDF_SMP_Move_from_scheduled_to_ready,
+    _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
     _Scheduler_EDF_SMP_Get_lowest_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -510,7 +541,9 @@ static inline void _Scheduler_EDF_SMP_Enqueue_scheduled(
     _Scheduler_EDF_SMP_Insert_ready,
     _Scheduler_EDF_SMP_Insert_scheduled,
     _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -527,7 +560,8 @@ void _Scheduler_EDF_SMP_Unblock(
     thread,
     node,
     _Scheduler_EDF_SMP_Do_update,
-    _Scheduler_EDF_SMP_Enqueue
+    _Scheduler_EDF_SMP_Enqueue,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -546,7 +580,8 @@ static inline bool _Scheduler_EDF_SMP_Do_ask_for_help(
     _Scheduler_EDF_SMP_Insert_scheduled,
     _Scheduler_EDF_SMP_Move_from_scheduled_to_ready,
     _Scheduler_EDF_SMP_Get_lowest_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -616,7 +651,9 @@ void _Scheduler_EDF_SMP_Withdraw_node(
     _Scheduler_EDF_SMP_Extract_from_ready,
     _Scheduler_EDF_SMP_Get_highest_ready,
     _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -649,7 +686,9 @@ void _Scheduler_EDF_SMP_Clean_sticky(
     _Scheduler_EDF_SMP_Extract_from_ready,
     _Scheduler_EDF_SMP_Get_highest_ready,
     _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
-    _Scheduler_EDF_SMP_Allocate_processor
+    _Scheduler_EDF_SMP_Allocate_processor,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -695,7 +734,9 @@ Thread_Control *_Scheduler_EDF_SMP_Remove_processor(
     cpu,
     _Scheduler_EDF_SMP_Extract_from_scheduled,
     _Scheduler_EDF_SMP_Extract_from_ready,
-    _Scheduler_EDF_SMP_Enqueue
+    _Scheduler_EDF_SMP_Enqueue,
+    _Scheduler_EDF_SMP_Get_idle,
+    _Scheduler_EDF_SMP_Release_idle
   );
 }
 
@@ -833,7 +874,9 @@ Status_Control _Scheduler_EDF_SMP_Set_affinity(
       _Scheduler_EDF_SMP_Get_highest_ready,
       _Scheduler_EDF_SMP_Move_from_ready_to_scheduled,
       _Scheduler_EDF_SMP_Enqueue,
-      _Scheduler_EDF_SMP_Allocate_processor
+      _Scheduler_EDF_SMP_Allocate_processor,
+      _Scheduler_EDF_SMP_Get_idle,
+      _Scheduler_EDF_SMP_Release_idle
     );
   }