Documentation for sub atomic-fetch
assembled from the following pages:
Class: Scalar §
From Scalar
(Scalar) sub atomic-fetch §
multi sub atomic-fetch( is rw)
Performs an atomic read of the value in the Scalar
$target
and returns the read value. Using this routine instead of simply using the variable ensures that the latest update to the variable from other threads will be seen, both by doing any required hardware barriers and also preventing the compiler from lifting reads. For example:
my = False;start until atomic-fetch()
Is certain to terminate, while in:
my = False;start until
It would be legal for a compiler to observe that $started
is not updated in the loop, and so lift the read out of the loop, thus causing the program to never terminate.
Class: atomicint §
From atomicint
(atomicint) sub atomic-fetch §
Defined as:
multi sub atomic-fetch(atomicint $ is rw)
Performs an atomic read of a native integer, which may live in a lexical, attribute, or native array element. Using this routine instead of simply using the variable ensures that the latest update to the variable from other threads will be seen, both by doing any required hardware barriers and also preventing the compiler from lifting reads. For example:
my atomicint = 0;start while atomic-fetch() == 0
Is certain to terminate, while in:
my atomicint = 0;start while == 0
It would be legal for a compiler to observe that $i
is not updated in the loop, and so lift the read out of the loop, thus causing the program to never terminate.