Data.Atomics.Internal

This module provides only the raw primops (and necessary types) for atomic operations.

Documentation

casIntArray# :: MutableByteArray# s -> Int# -> Int# -> Int# -> State# s -> (#State# s, Int##)

fetchAddIntArray# :: MutableByteArray# s -> Int# -> Int# -> State# s -> (#State# s, Int##)

readForCAS# :: MutVar# RealWorld a -> State# RealWorld -> (#State# RealWorld, Ticket a#)

casMutVarTicketed# :: MutVar# RealWorld a -> Ticket a -> Ticket a -> State# RealWorld -> (#State# RealWorld, Int#, Ticket a#)

casArrayTicketed# :: MutableArray# RealWorld a -> Int# -> Ticket a -> Ticket a -> State# RealWorld -> (#State# RealWorld, Int#, Ticket a#)

Unsafe, machine-level atomic compare and swap on an element within an Array.

type Ticket a = Any a

When performing compare-and-swaps, the ticket encapsulates proof that a thread observed a specific previous value of a mutable variable. It is provided in lieu of the old value to compare-and-swap.

Design note: Tickets exist to hide objects from the GHC compiler, which can normally perform many optimizations that change pointer equality. A Ticket, on the other hand, is a first-class object that can be handled by the user, but will not have its pointer identity changed by compiler optimizations (but will of course, change addresses during garbage collection).

Very unsafe, not to be used

ptrEq :: a -> a -> Bool