D.13 The Ravenscar and Jorvik Profiles
This subclause defines the Ravenscar and Jorvik
profiles.
Legality Rules
Static Semantics
The usage profile Ravenscar
is equivalent to the following set of pragmas:
pragma Task_Dispatching_Policy (FIFO_Within_Priorities);
pragma Locking_Policy (Ceiling_Locking);
pragma Detect_Blocking;
pragma Restrictions (
No_Abort_Statements,
No_Dynamic_Attachment,
No_Dynamic_CPU_Assignment,
No_Dynamic_Priorities,
No_Implicit_Heap_Allocations,
No_Local_Protected_Objects,
No_Local_Timing_Events,
No_Protected_Type_Allocators,
No_Relative_Delay,
No_Requeue_Statements,
No_Select_Statements,
No_Specific_Termination_Handlers,
No_Task_Allocators,
No_Task_Hierarchy,
No_Task_Termination,
Simple_Barriers,
Max_Entry_Queue_Length => 1,
Max_Protected_Entries => 1,
Max_Task_Entries => 0,
No_Dependence => Ada.Asynchronous_Task_Control,
No_Dependence => Ada.Calendar,
No_Dependence => Ada.Execution_Time.Group_Budgets,
No_Dependence => Ada.Execution_Time.Timers,
No_Dependence => Ada.Synchronous_Barriers,
No_Dependence => Ada.Task_Attributes,
No_Dependence => System.Multiprocessors.Dispatching_Domains);
The usage profile
Jorvik is equivalent to the following set of pragmas:
pragma Task_Dispatching_Policy (FIFO_Within_Priorities);
pragma Locking_Policy (Ceiling_Locking);
pragma Detect_Blocking;
pragma Restrictions (
No_Abort_Statements,
No_Dynamic_Attachment,
No_Dynamic_CPU_Assignment,
No_Dynamic_Priorities,
No_Local_Protected_Objects,
No_Local_Timing_Events,
No_Protected_Type_Allocators,
No_Requeue_Statements,
No_Select_Statements,
No_Specific_Termination_Handlers,
No_Task_Allocators,
No_Task_Hierarchy,
No_Task_Termination,
Pure_Barriers,
Max_Task_Entries => 0,
No_Dependence => Ada.Asynchronous_Task_Control,
No_Dependence => Ada.Execution_Time.Group_Budgets,
No_Dependence => Ada.Execution_Time.Timers,
No_Dependence => Ada.Task_Attributes,
No_Dependence => System.Multiprocessors.Dispatching_Domains);
Paragraph 7 was deleted.
Implementation Requirements
This paragraph was
deleted.
Implementation Advice
On a multiprocessor system, an implementation should
support a fully partitioned approach if one of these profiles is specified.
Each processor should have separate and disjoint ready queues.
41 For the Ravenscar profile, the effect
of the restriction Max_Entry_Queue_Length => 1 applies only to protected
entry queues due to the accompanying restriction Max_Task_Entries =>
0. The restriction Max_Entry_Queue_Length is not applied by the Jorvik
profile.
42 When the Ravenscar or Jorvik profile
is in effect (via the effect of the No_Dynamic_CPU_Assignment restriction),
all of the tasks in the partition will execute on a single CPU unless
the programmer explicitly uses aspect CPU to specify the CPU assignments
for tasks. The use of multiple CPUs requires care, as many guarantees
of single CPU scheduling no longer apply.
43 It is not recommended to specify the
CPU of a task to be Not_A_Specific_CPU when the Ravenscar or Jorvik profile
is in effect. How a partition executes strongly depends on the assignment
of tasks to CPUs.
44 Any unit that meets the requirements
of the Ravenscar profile also meets the requirements of the Yorvik profile.
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