D.5.2 Dynamic Priorities for Protected Objects
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{
AI95-00327-01}
This clause specifies how the priority of a protected
object can be modified or queried at run time. Static Semantics
2/2
{
AI95-00327-01}
The following attribute is defined for a prefix
P that denotes a protected object:3/2
P'Priority
{
AI95-00327-01}
Denotes a non-aliased
component of the protected object P. This component is of type System.Any_Priority
and its value is the priority of P. P'Priority denotes a variable if
and only if P denotes a variable. A reference to this attribute shall
appear only within the body of P.
4/2
{
AI95-00327-01}
The initial value of this attribute is the initial
value of the priority of the protected object[, and can be changed by
an assignment]. Dynamic Semantics
5/3
{
AI95-00327-01}
{
AI05-0264-1}
If the locking policy Ceiling_Locking (see D.3)
is in effect, then the ceiling priority of a protected object P is set to the
value of P'Priority at the end of each protected action of P.6/3
{
AI95-00445-01}
{
AI05-0229-1}
If the locking policy Ceiling_Locking is in effect,
then for a protected object P with either an Attach_Handler or
Interrupt_Handler aspect specified for pragma
applying to one of its procedures,
a check is made that the value to be assigned to P'Priority is
in the range System.Interrupt_Priority. If the check fails, Program_Error
is raised. Metrics
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{
AI95-00327-01}
The implementation shall document the following
metric:8/2
The
difference in execution time of calls to the following procedures in
protected object P:
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protected P is
procedure Do_Not_Set_Ceiling (Pr : System.Any_Priority);
procedure Set_Ceiling (Pr : System.Any_Priority);
end P;
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protected body P is
procedure Do_Not_Set_Ceiling (Pr : System.Any_Priority) is
begin
null;
end;
procedure Set_Ceiling (Pr : System.Any_Priority) is
begin
P'Priority := Pr;
end;
end P;
10.a/2
Documentation Requirement:
The metrics for setting the priority
of a protected object.
11/2
34 {
AI95-00327-01}
Since P'Priority is a normal variable, the value
following an assignment to the attribute immediately reflects the new
value even though its impact on the ceiling priority of P is postponed
until completion of the protected action in which it is executed.
Extensions to Ada 95
11.a/2
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
