score: Introduce CPU budget operations

This patch set replaces the CPU budget algorithm enumeration with a set of CPU
budget operations which implement a particular CPU budget algorithm.  This
helps to hide the CPU budget algorithm implementation details from the general
thread handling.  The CPU budget callouts are turned into CPU budget
operations.  This slightly reduces the size of the thread control block.

All schedulers used the default scheduler tick implementation.  The tick
scheduler operation is removed and the CPU budget operations are directly used
in _Watchdog_Tick() if the executing thread uses a CPU budget algorithm.  This
is performance improvement for all threads which do not use a CPU budget
algorithm (default behaviour).

5 files changed, 85 insertions, 49 deletions

diff --git a/cpukit/posix/src/psxtransschedparam.c b/cpukit/posix/src/psxtransschedparam.c
index eba26d4932..f97924e011 100644
--- a/cpukit/posix/src/psxtransschedparam.c
+++ b/cpukit/posix/src/psxtransschedparam.c
@@ -23,22 +23,27 @@
 #include <errno.h>
 
 #include <rtems/posix/pthreadimpl.h>
+#include <rtems/score/threadcpubudget.h>
 
 int _POSIX_Thread_Translate_to_sched_policy(
-  Thread_CPU_budget_algorithms budget_algorithm
+  const Thread_CPU_budget_operations *operations
 )
 {
-  switch ( budget_algorithm ) {
-    case THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE:
-      return SCHED_OTHER;
-    case THREAD_CPU_BUDGET_ALGORITHM_EXHAUST_TIMESLICE:
-      return SCHED_RR;
-    case THREAD_CPU_BUDGET_ALGORITHM_CALLOUT:
-      return SCHED_SPORADIC;
-    default:
-      _Assert( budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_NONE );
-      return SCHED_FIFO;
+  if ( operations == NULL ) {
+    return SCHED_FIFO;
   }
+
+  if ( operations == &_Thread_CPU_budget_exhaust_timeslice ) {
+    return SCHED_RR;
+  }
+
+#if defined(RTEMS_POSIX_API)
+  if ( operations == &_POSIX_Threads_Sporadic_budget ) {
+    return SCHED_SPORADIC;
+  }
+#endif
+
+  return SCHED_OTHER;
 }
 
 int _POSIX_Thread_Translate_sched_param(
@@ -47,23 +52,19 @@ int _POSIX_Thread_Translate_sched_param(
   Thread_Configuration     *config
 )
 {
-  config->budget_algorithm = THREAD_CPU_BUDGET_ALGORITHM_NONE;
-  config->budget_callout = NULL;
-  config->cpu_time_budget = 0;
+  config->cpu_budget_operations = NULL;
 
-  if ( policy == SCHED_OTHER ) {
-    config->budget_algorithm = THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE;
+  if ( policy == SCHED_FIFO ) {
     return 0;
   }
 
-  if ( policy == SCHED_FIFO ) {
-    config->budget_algorithm = THREAD_CPU_BUDGET_ALGORITHM_NONE;
+  if ( policy == SCHED_OTHER ) {
+    config->cpu_budget_operations = &_Thread_CPU_budget_reset_timeslice;
     return 0;
   }
 
   if ( policy == SCHED_RR ) {
-    config->budget_algorithm = THREAD_CPU_BUDGET_ALGORITHM_EXHAUST_TIMESLICE;
-    config->cpu_time_budget = rtems_configuration_get_ticks_per_timeslice();
+    config->cpu_budget_operations = &_Thread_CPU_budget_exhaust_timeslice;
     return 0;
   }
 
@@ -81,8 +82,7 @@ int _POSIX_Thread_Translate_sched_param(
 	 _Timespec_To_ticks( &param->sched_ss_init_budget ) )
       return EINVAL;
 
-    config->budget_algorithm  = THREAD_CPU_BUDGET_ALGORITHM_CALLOUT;
-    config->budget_callout = _POSIX_Threads_Sporadic_budget_callout;
+    config->cpu_budget_operations = &_POSIX_Threads_Sporadic_budget;
     return 0;
   }
 #endif
diff --git a/cpukit/posix/src/pthreadcreate.c b/cpukit/posix/src/pthreadcreate.c
index 9474d07032..093ad5cfe1 100644
--- a/cpukit/posix/src/pthreadcreate.c
+++ b/cpukit/posix/src/pthreadcreate.c
@@ -34,9 +34,11 @@
 #include <rtems/posix/pthreadimpl.h>
 #include <rtems/posix/pthreadattrimpl.h>
 #include <rtems/score/assert.h>
+#include <rtems/score/threadcpubudget.h>
 #include <rtems/score/threadimpl.h>
 #include <rtems/score/apimutex.h>
 #include <rtems/score/stackimpl.h>
+#include <rtems/score/statesimpl.h>
 #include <rtems/score/schedulerimpl.h>
 #include <rtems/score/userextimpl.h>
 #include <rtems/sysinit.h>
@@ -348,7 +350,9 @@ void _POSIX_Threads_Sporadic_timer( Watchdog_Control *watchdog )
   _Thread_Priority_update( &queue_context );
 }
 
-void _POSIX_Threads_Sporadic_budget_callout( Thread_Control *the_thread )
+static void _POSIX_Threads_Sporadic_budget_callout(
+  Thread_Control *the_thread
+)
 {
   POSIX_API_Control    *api;
   Thread_queue_Context  queue_context;
@@ -363,7 +367,7 @@ void _POSIX_Threads_Sporadic_budget_callout( Thread_Control *the_thread )
    *  This will prevent the thread from consuming its entire "budget"
    *  while at low priority.
    */
-  the_thread->cpu_time_budget = UINT32_MAX;
+  the_thread->CPU_budget.available = UINT32_MAX;
 
   if ( !_Priority_Node_is_active( &api->Sporadic.Low_priority ) ) {
     _Thread_Priority_add(
@@ -382,6 +386,34 @@ void _POSIX_Threads_Sporadic_budget_callout( Thread_Control *the_thread )
   _Thread_Priority_update( &queue_context );
 }
 
+static void _POSIX_Threads_Sporadic_budget_at_tick( Thread_Control *the_thread )
+{
+  uint32_t budget_available;
+
+  if ( !the_thread->is_preemptible ) {
+    return;
+  }
+
+  if ( !_States_Is_ready( the_thread->current_state ) ) {
+    return;
+  }
+
+  budget_available = the_thread->CPU_budget.available;
+
+  if ( budget_available == 1 ) {
+    the_thread->CPU_budget.available = 0;
+    _POSIX_Threads_Sporadic_budget_callout ( the_thread );
+  } else {
+    the_thread->CPU_budget.available = budget_available - 1;
+  }
+}
+
+const Thread_CPU_budget_operations _POSIX_Threads_Sporadic_budget = {
+  .at_tick = _POSIX_Threads_Sporadic_budget_at_tick,
+  .at_context_switch = _Thread_CPU_budget_do_nothing,
+  .initialize = _Thread_CPU_budget_do_nothing
+};
+
 static bool _POSIX_Threads_Create_extension(
   Thread_Control *executing,
   Thread_Control *created
diff --git a/cpukit/posix/src/pthreadgetattrnp.c b/cpukit/posix/src/pthreadgetattrnp.c
index 5572fb98a5..aa34185264 100644
--- a/cpukit/posix/src/pthreadgetattrnp.c
+++ b/cpukit/posix/src/pthreadgetattrnp.c
@@ -37,12 +37,12 @@ int pthread_getattr_np(
   pthread_attr_t *attr
 )
 {
-  Thread_Control               *the_thread;
-  ISR_lock_Context              lock_context;
-  Thread_CPU_budget_algorithms  budget_algorithm;
-  const Scheduler_Control      *scheduler;
-  Priority_Control              priority;
-  Status_Control                status;
+  Thread_Control                     *the_thread;
+  ISR_lock_Context                    lock_context;
+  const Thread_CPU_budget_operations *cpu_budget_operations;
+  const Scheduler_Control            *scheduler;
+  Priority_Control                    priority;
+  Status_Control                      status;
 
   if ( attr == NULL ) {
     return EINVAL;
@@ -89,7 +89,7 @@ int pthread_getattr_np(
     attr->affinityset
   );
 
-  budget_algorithm = the_thread->budget_algorithm;
+  cpu_budget_operations = the_thread->CPU_budget.operations;
 
   _Thread_State_release( the_thread, &lock_context );
 
@@ -101,7 +101,7 @@ int pthread_getattr_np(
     priority
   );
   attr->schedpolicy =
-    _POSIX_Thread_Translate_to_sched_policy( budget_algorithm );
+    _POSIX_Thread_Translate_to_sched_policy( cpu_budget_operations );
 
   return _POSIX_Get_error( status );
 }
diff --git a/cpukit/posix/src/pthreadgetschedparam.c b/cpukit/posix/src/pthreadgetschedparam.c
index a82d79c715..406ae8e7bb 100644
--- a/cpukit/posix/src/pthreadgetschedparam.c
+++ b/cpukit/posix/src/pthreadgetschedparam.c
@@ -37,11 +37,11 @@ int pthread_getschedparam(
   struct sched_param *param
 )
 {
-  Thread_Control               *the_thread;
-  Thread_queue_Context          queue_context;
-  Thread_CPU_budget_algorithms  budget_algorithm;
-  const Scheduler_Control      *scheduler;
-  Priority_Control              priority;
+  Thread_Control                     *the_thread;
+  Thread_queue_Context                queue_context;
+  const Thread_CPU_budget_operations *cpu_budget_operations;
+  const Scheduler_Control            *scheduler;
+  Priority_Control                    priority;
 
   if ( policy == NULL || param == NULL ) {
     return EINVAL;
@@ -59,11 +59,11 @@ int pthread_getschedparam(
   scheduler = _Thread_Scheduler_get_home( the_thread );
   _POSIX_Threads_Get_sched_param_sporadic( the_thread, scheduler, param );
   priority = the_thread->Real_priority.priority;
-  budget_algorithm = the_thread->budget_algorithm;
+  cpu_budget_operations = the_thread->CPU_budget.operations;
 
   _Thread_Wait_release( the_thread, &queue_context );
 
   param->sched_priority = _POSIX_Priority_From_core( scheduler, priority );
-  *policy = _POSIX_Thread_Translate_to_sched_policy( budget_algorithm );
+  *policy = _POSIX_Thread_Translate_to_sched_policy( cpu_budget_operations );
   return 0;
 }
diff --git a/cpukit/posix/src/pthreadsetschedparam.c b/cpukit/posix/src/pthreadsetschedparam.c
index 1c207e7887..165e1d86a8 100644
--- a/cpukit/posix/src/pthreadsetschedparam.c
+++ b/cpukit/posix/src/pthreadsetschedparam.c
@@ -40,14 +40,15 @@ static int _POSIX_Set_sched_param(
   Thread_queue_Context       *queue_context
 )
 {
-  const Scheduler_Control *scheduler;
-  int                      normal_prio;
-  bool                     valid;
-  Priority_Control         core_normal_prio;
+  const Scheduler_Control            *scheduler;
+  int                                 normal_prio;
+  bool                                valid;
+  Priority_Control                    core_normal_prio;
+  const Thread_CPU_budget_operations *cpu_budget_operations;
 #if defined(RTEMS_POSIX_API)
-  POSIX_API_Control       *api;
-  int                      low_prio;
-  Priority_Control         core_low_prio;
+  POSIX_API_Control                  *api;
+  int                                 low_prio;
+  Priority_Control                    core_low_prio;
 #endif
 
   normal_prio = param->sched_priority;
@@ -103,9 +104,12 @@ static int _POSIX_Set_sched_param(
   }
 #endif
 
-  the_thread->cpu_time_budget  = config->cpu_time_budget;
-  the_thread->budget_algorithm = config->budget_algorithm;
-  the_thread->budget_callout   = config->budget_callout;
+  cpu_budget_operations = config->cpu_budget_operations;
+  the_thread->CPU_budget.operations = cpu_budget_operations;
+
+  if ( cpu_budget_operations != NULL ) {
+    ( *cpu_budget_operations->initialize )( the_thread );
+  }
 
 #if defined(RTEMS_POSIX_API)
   _Priority_Node_set_priority( &api->Sporadic.Low_priority, core_low_prio );