D.10.1 Synchronous Barriers

{AI05-0174-1} {AI05-0299-1} This subclause introduces a language-defined package to synchronously release a group of tasks after the number of blocked tasks reaches a specified count value. 

{AI05-0174-1} The following language-defined library package exists: 

{AI05-0174-1} Type Synchronous_Barrier needs finalization (see 7.6).

{AI05-0174-1} 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.

{AI05-0174-1} The mechanism for determining which task sets Notified to True is implementation defined.

{AI05-0174-1} Once all tasks have been released, a Synchronous_Barrier object may be reused to block another Release_Threshold number of tasks.

{AI05-0174-1} 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.

{AI05-0174-1} 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. 

{AI05-0174-1} Wait_For_Release is a potentially blocking operation (see 9.5.1).

{AI05-0174-1} 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.