Package Info


A safe approach to CAS and other atomic ops in Haskell


After GHC 7.4 a new casMutVar# primop became available, but it's difficult to use safely, because pointer equality is a highly unstable property in Haskell. This library provides a safer method based on the concept of "Tickets".

Also, this library uses the "foreign primop" capability of GHC to add access to other variants that may be of interest, specifically, compare and swap inside an array.

Note that as of GHC 7.8, the relevant primops have been included in GHC itself. This library is engineered to work pre- and post-GHC-7.8, while exposing the same interface.

Changes in 0.3:

  • Major internal change. Duplicate the barrier code from the GHC RTS and thus

enable support for executables that are NOT built with '-threaded'.

Changes in 0.4:

  • Further internal changes, duplicate 'cas' routine well as barriers.

  • Add fetchAddByteArrayInt

  • Add an Unboxed counter variant that uses movable "ByteArray"s on the GHC


Changes in 0.5:

  • Remove dependency on bits-atomic unless a flag is turned on.

Changes in

  • IMPORTANT BUGFIXES - don't use earlier versions. They have been marked


Changes in 0.6.1

  • This is a good version to use for GHC 7.8.3. It includes portability and bug

fixes and adds atomicModifyIORefCAS.

Changes in 0.7:

  • This release adds support for GHC 7.10 and its expanded library of (now

inline) primops.

Changes in 0.8:

  • Implements additional fetch primops available in GHC 7.10

Changes in

  • Internal changes to support forthcoming GHC 8.0.

License: BSD-3-Clause



Package Version Update ID Released Package Hub Version Platforms Subpackages
0.8.4-bp154.1.12 info GA Release 2022-05-09 15 SP4
  • AArch64
  • ppc64le
  • x86-64
  • ghc-atomic-primops
  • ghc-atomic-primops-devel info GA Release 2018-07-30 15
  • AArch64
  • ppc64le
  • x86-64
  • ghc-atomic-primops
  • ghc-atomic-primops-devel