H.6 Pragma Partition_Elaboration_Policy
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Syntax
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pragma
Partition_Elaboration_Policy
(policy_identifier);
4/2
The policy_identifier
shall be either Sequential, Concurrent or an implementation-defined identifier.
4.a/2
Implementation defined:
Implementation-defined policy_identifiers
allowed in a pragma
Partition_Elaboration_Policy.
Post-Compilation Rules
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AI95-00265-01}
A pragma
Partition_Elaboration_Policy is a configuration pragma. It specifies
the elaboration policy for a partition. At most one elaboration policy
shall be specified for a partition.6/3
{
AI95-00265-01}
{
AI05-0264-1}
If the Sequential policy is specified for a partition, then pragma Restrictions (No_Task_Hierarchy) shall also be specified
for the partition. Dynamic Semantics
7/2
{
AI95-00265-01}
Notwithstanding what this International
Standard says elsewhere, this pragma
allows partition elaboration rules concerning task activation and interrupt
attachment to be changed. If the policy_identifier
is Concurrent, or if there is no pragma Partition_Elaboration_Policy
defined for the partition, then the rules defined elsewhere in this Standard
apply.8/2
{
AI95-00265-01}
{
AI95-00421-01}
If the partition elaboration policy is Sequential,
then task activation and interrupt attachment are performed in the following
sequence of steps:9/2
The activation of all library-level
tasks and the attachment of interrupt handlers are deferred until all
library units are elaborated.
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The interrupt handlers are
attached by the environment task.
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The environment task is suspended
while the library-level tasks are activated.
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The environment task executes
the main subprogram (if any) concurrently with these executing tasks.
13/2
{
AI95-00265-01}
{
AI95-00421-01}
If several dynamic interrupt handler attachments
for the same interrupt are deferred, then the most recent call of Attach_Handler
or Exchange_Handler determines which handler is attached.14/2
{
AI95-00265-01}
{
AI95-00421-01}
If any deferred task activation fails, Tasking_Error
is raised at the beginning of the sequence of statements of the body
of the environment task prior to calling the main subprogram.Implementation Advice
15/3
{
AI95-00265-01}
{
AI05-0264-1}
If the partition elaboration policy is Sequential
and the Environment task becomes permanently blocked during elaboration, then the partition is deadlocked and it is recommended that the partition
be immediately terminated. 15.a/3
Implementation Advice: If
the partition elaboration policy is Sequential and the Environment task
becomes permanently blocked during elaboration, then the partition should be immediately terminated.
Implementation Permissions
16/3
{
AI95-00265-01}
{
AI05-0264-1}
If the partition elaboration policy is Sequential
and any task activation fails, then an implementation may immediately terminate the active partition
to mitigate the hazard posed by continuing to execute with a subset of
the tasks being active. 17/2
12 {
AI95-00421-01}
If any deferred task activation fails, the environment
task is unable to handle the Tasking_Error exception and completes immediately.
By contrast, if the partition elaboration policy is Concurrent, then
this exception could be handled within a library unit. Extensions to Ada 95
17.a/2
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
