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D.13 The Ravenscar Profile

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This subclause defines the Ravenscar profile.
Paragraphs 2 and 3 were moved to 13.12, “Pragma Restrictions and Pragma Profile”. 

Legality Rules

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The profile_identifier Ravenscar is a usage profile (see 13.12). For usage profile Ravenscar, there shall be no profile_pragma_argument_associations.

Static Semantics

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The usage profile Ravenscar is equivalent to the following set of pragmas:
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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);
Paragraph 7 was deleted.

Implementation Requirements

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This paragraph was deleted.

Implementation Advice

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On a multiprocessor system, an implementation should support a fully partitioned approach. Each processor should have separate and disjoint ready queues.
NOTES
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42  The effect of the Max_Entry_Queue_Length => 1 restriction applies only to protected entry queues due to the accompanying restriction of Max_Task_Entries => 0.
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43  When the Ravenscar 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.
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44  It is not recommended to specify the CPU of a task to be Not_A_Specific_CPU when the Ravenscar profile is in effect. How a partition executes strongly depends on the assignment of tasks to CPUs. 

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