score: Rework _Thread_Change_priority()

Move the writes to Thread_Control::current_priority and
Thread_Control::real_priority into _Thread_Change_priority() under the
protection of the thread lock.  Add a filter function to
_Thread_Change_priority() to enable specialized variants.

Avoid race conditions during a thread priority restore with the new
Thread_Control::priority_restore_hint for an important average case
optimizations used by priority inheritance mutexes.

Update #2273.

1 files changed, 12 insertions, 7 deletions

diff --git a/cpukit/score/src/coremutex.c b/cpukit/score/src/coremutex.c
index 58c6c42b06..6bb535a8ec 100644
--- a/cpukit/score/src/coremutex.c
+++ b/cpukit/score/src/coremutex.c
@@ -50,15 +50,20 @@ CORE_mutex_Status _CORE_mutex_Initialize(
       Priority_Control ceiling = the_mutex->Attributes.priority_ceiling;
       Per_CPU_Control *cpu_self;
 
-      /*
-       * The mutex initialization is only protected by the allocator lock in
-       * general.  Disable thread dispatching before the priority check to
-       * prevent interference with priority inheritance.
-       */
+      /* The mutex initialization is only protected by the allocator lock */
       cpu_self = _Thread_Dispatch_disable();
 
+      /*
+       * The test to check for a ceiling violation is a bit arbitrary.  In case
+       * this thread is the owner of a priority inheritance mutex, then it may
+       * get a higher priority later or anytime on SMP configurations.
+       */
       if ( is_priority_ceiling && executing->current_priority < ceiling ) {
-        _Thread_Enable_dispatch();
+        /*
+         * There is no need to undo the previous work since this error aborts
+         * the object creation.
+         */
+        _Thread_Dispatch_enable( cpu_self );
         return CORE_MUTEX_STATUS_CEILING_VIOLATED;
       }
 
@@ -71,7 +76,7 @@ CORE_mutex_Status _CORE_mutex_Initialize(
       executing->resource_count++;
 
       if ( is_priority_ceiling ) {
-        _Thread_Change_priority( executing, ceiling, false );
+        _Thread_Raise_priority( executing, ceiling );
       }
 
       _Thread_Dispatch_enable( cpu_self );