C.6.1 The Package System.Atomic_Operations
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The language-defined package System.Atomic_Operations is the parent of
a set of child units that provide facilities for manipulating objects
of atomic types and for supporting lock-free synchronization. The subprograms
of this subsystem are Intrinsic subprograms (see
6.3.1)
in order to provide convenient access to machine operations that can
provide these capabilities if they are available in the target environment.
Static Semantics
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The library package System.Atomic_Operations has the following declaration:
package System.Atomic_Operations
with Pure, Nonblocking
is
end System.Atomic_Operations;
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System.Atomic_Operations serves as the parent of other language-defined
library units that manipulate atomic objects; its declaration is empty.
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A call to a subprogram is said to be
lock-free
if the subprogram is guaranteed to return from the call while keeping
the processor of the logical thread of control busy for the duration
of the call.
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In each child package, a function Is_Lock_Free(...) is provided to check
whether the operations of the child package can all be provided lock-free
for a given object. Is_Lock_Free returns True if operations defined in
the child package are lock-free when applied to the object denoted by
Item, and Is_Lock_Free returns False otherwise.
Extensions to Ada 2012
Ada 2005 and 2012 Editions sponsored in part by Ada-Europe
