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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Two-stage suspend operations
Date: Sat, 07 May 2016 17:13:17 +0100
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Date: 2016-05-07T17:13:17+01:00
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ARM D.10 says (since Ada95)

   This subclause describes a language-defined private semaphore
   (suspension object), which can be used for two-stage suspend
   operations and as a simple building block for implementing
   higher-level queues.

I've spent some time googling "two-stage suspend operations" and come up
empty. I did eventually think to look in the Ada 95 Rationale, and there
is an explanation in the corresponding section of Part 3 (which I will
have to think about some more):
http://www.adaic.org/resources/add_content/standards/95rat/rat95html/rat95-p3-d.html#10

Has anyone any other references?