posix: Rework sporadic server scheduling policy

Instead of lowering the priority in case the initial budget is consumed
raise the priority for each new period.  Restore the normal priority
once the initial budget is consumed.  This makes it later easier to
combine the high priority phase with temporary priority boosts (e.g. via
priority ceiling and inheritance).

Use the thread lock to protect the POSIX thread attributes instead of
the thread state lock.  This makes it easier to change the thread
priority and keep the POSIX attributes consistent.

Fixes a false positive use of uninitialized variable warning.

1 files changed, 31 insertions, 17 deletions

diff --git a/cpukit/posix/src/pthreadcreate.c b/cpukit/posix/src/pthreadcreate.c
index c7c233857a..f2fc1ca68e 100644
--- a/cpukit/posix/src/pthreadcreate.c
+++ b/cpukit/posix/src/pthreadcreate.c
@@ -60,7 +60,10 @@ int pthread_create(
     }
   };
   const pthread_attr_t               *the_attr;
-  Priority_Control                    core_priority;
+  int                                 low_prio;
+  int                                 high_prio;
+  Priority_Control                    core_low_prio;
+  Priority_Control                    core_high_prio;
   Thread_CPU_budget_algorithms        budget_algorithm;
   Thread_CPU_budget_algorithm_callout budget_callout;
   bool                                is_fp;
@@ -71,7 +74,7 @@ int pthread_create(
   int                                 schedpolicy = SCHED_RR;
   struct sched_param                  schedparam;
   Objects_Name                        name;
-  int                                 rc;
+  int                                 error;
   ISR_lock_Context                    lock_context;
 
   if ( !start_routine )
@@ -130,25 +133,34 @@ int pthread_create(
   if ( the_attr->contentionscope != PTHREAD_SCOPE_PROCESS )
     return ENOTSUP;
 
-  /*
-   *  Interpret the scheduling parameters.
-   */
-  if ( !_POSIX_Priority_Is_valid( schedparam.sched_priority ) )
-    return EINVAL;
-
-  core_priority = _POSIX_Priority_To_core( schedparam.sched_priority );
-
-  /*
-   *  Set the core scheduling policy information.
-   */
-  rc = _POSIX_Thread_Translate_sched_param(
+  error = _POSIX_Thread_Translate_sched_param(
     schedpolicy,
     &schedparam,
     &budget_algorithm,
     &budget_callout
   );
-  if ( rc )
-    return rc;
+  if ( error != 0 ) {
+    return error;
+  }
+
+  if ( schedpolicy == SCHED_SPORADIC ) {
+    low_prio = schedparam.sched_ss_low_priority;
+    high_prio = schedparam.sched_priority;
+  } else {
+    low_prio = schedparam.sched_priority;
+    high_prio = low_prio;
+  }
+
+  if ( !_POSIX_Priority_Is_valid( low_prio ) ) {
+    return EINVAL;
+  }
+
+  if ( !_POSIX_Priority_Is_valid( high_prio ) ) {
+    return EINVAL;
+  }
+
+  core_low_prio = _POSIX_Priority_To_core( low_prio );
+  core_high_prio = _POSIX_Priority_To_core( high_prio );
 
 #if defined(RTEMS_SMP)
 #if __RTEMS_HAVE_SYS_CPUSET_H__
@@ -186,7 +198,7 @@ int pthread_create(
     the_attr->stackaddr,
     _POSIX_Threads_Ensure_minimum_stack(the_attr->stacksize),
     is_fp,
-    core_priority,
+    core_high_prio,
     true,                 /* preemptible */
     budget_algorithm,
     budget_callout,
@@ -226,6 +238,8 @@ int pthread_create(
   api = the_thread->API_Extensions[ THREAD_API_POSIX ];
 
   _POSIX_Threads_Copy_attributes( &api->Attributes, the_attr );
+  api->Sporadic.low_priority = core_low_prio;
+  api->Sporadic.high_priority = core_high_prio;
 
   if ( schedpolicy == SCHED_SPORADIC ) {
     _ISR_lock_ISR_disable( &lock_context );