score: Add and use PRIORITY_PSEUDO_ISR

cpukit/rtems/src/timerserver.c

@@ -481,7 +481,7 @@ rtems_status_code rtems_timer_initiate_server(
   if ( !_RTEMS_tasks_Priority_is_valid( priority ) ) {
     if ( priority != RTEMS_TIMER_SERVER_DEFAULT_PRIORITY )
       return RTEMS_INVALID_PRIORITY;
-    _priority = 0;
+    _priority = PRIORITY_PSEUDO_ISR;
   }
 
   /*

cpukit/score/include/rtems/score/priority.h

@@ -58,6 +58,13 @@ typedef uint32_t   Priority_Control;
 /** This defines the highest (most important) thread priority. */
 #define PRIORITY_MINIMUM      0
 
+/**
+ * @brief This defines the priority of pseudo-ISR threads.
+ *
+ * Examples are the MPCI and timer server threads.
+ */
+#define PRIORITY_PSEUDO_ISR   PRIORITY_MINIMUM
+
 /** This defines the default lowest (least important) thread priority. */
 #if defined (CPU_PRIORITY_MAXIMUM)
   #define PRIORITY_DEFAULT_MAXIMUM      CPU_PRIORITY_MAXIMUM

cpukit/score/src/mpci.c

@@ -112,7 +112,7 @@ void _MPCI_Create_server( void )
       CPU_MPCI_RECEIVE_SERVER_EXTRA_STACK +
       _Configuration_MP_table->extra_mpci_receive_server_stack,
     CPU_ALL_TASKS_ARE_FP,
-    PRIORITY_MINIMUM,
+    PRIORITY_PSEUDO_ISR,
     false,       /* no preempt */
     THREAD_CPU_BUDGET_ALGORITHM_NONE,
     NULL,        /* no budget algorithm callout */