PowerAda 93

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(93) Whether, on a multiprocessor, a task that is waiting for access to a protected object keeps its processor busy.

See D.2.1(3).

The PowerAda runtime implements the mutual exclusion of a protected object using POSIX mutexes. AIX POSIX mutexes are considered "low-contention objects", that is programs should not lock them for long periods. This is consistent with the Ada95 LM language in sections 9.5.1(8-22) where programs are proscribed from executing potentially blocking operations. That having been said, it does not appear that threads waiting on mutexes consume any CPU time in current versions of AIX. The user thread is marked as "running" but the kernel thread assigned to the user thread is marked as "blocked".