D.10.1 Synchronous Barriers
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This clause introduces a language-defined package
to synchronously release a group of tasks after the number of blocked
tasks reaches a specified count value. Static Semantics
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The following language-defined library package
exists: 3/3
package Ada.Synchronous_Barriers is
pragma Preelaborate(Synchronous_Barriers);
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subtype Barrier_Limit is Positive range 1 .. implementation-defined;
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Implementation defined:
The value of Barrier_Limit'Last in Synchronous_Barriers.
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type Synchronous_Barrier (Release_Threshold : Barrier_Limit) is limited private;
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procedure Wait_For_Release (The_Barrier : in out Synchronous_Barrier;
Notified : out Boolean);
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private
-- not specified by the language
end Ada.Synchronous_Barriers;
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Dynamic Semantics
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Each call to Wait_For_Release blocks the calling
task until the number of blocked tasks associated with the Synchronous_Barrier
object is equal to Release_Threshold, at which time all blocked tasks
are released. Notified is set to True for one of the released tasks,
and set to False for all other released tasks.10/3
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The mechanism for determining which task sets Notified
to True is implementation defined.11/3
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Once all tasks have been released, a Synchronous_Barrier
object may be reused to block another Release_Threshold number of tasks.12/3
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As the first step of the finalization of a Synchronous_Barrier,
each blocked task is unblocked and Program_Error is raised at the place
of the call to Wait_For_Release.13/3
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It is implementation defined whether an abnormal
task which is waiting on a Synchronous_Barrier object is aborted immediately
or aborted when the tasks waiting on the object are released.
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Implementation defined:
When an aborted task that is waiting
on a Synchronous_Barrier is aborted.
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Bounded (Run-Time) Errors
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It is a bounded error to call Wait_For_Release
on a Synchronous_Barrier object after that object is finalized. If the
error is detected, Program_Error is raised. Otherwise, the call proceeds
normally, which may leave a task blocked forever. Extensions to Ada 2005
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The package Ada.Synchronous_Barriers
is new.
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
