concurrency

Typeclasses, functions, and data types for concurrency and STM.

https://github.com/barrucadu/dejafu

Version on this page:1.11.0.2
LTS Haskell 22.39:1.11.0.3
Stackage Nightly 2024-10-31:1.11.0.3
Latest on Hackage:1.11.0.3

See all snapshots concurrency appears in

MIT licensed by Michael Walker
Maintained by [email protected]
This version can be pinned in stack with:concurrency-1.11.0.2@sha256:d3822ea3a560209b57f19ec3da36b8369f418fee59de3373c5a1584054ff8345,3078

Module documentation for 1.11.0.2

Used by 1 package in nightly-2022-08-02(full list with versions):
dejafu

concurrency

A typeclass abstraction over much of Control.Concurrent (and some extras!). If you’re looking for a general introduction to Haskell concurrency, you should check out the excellent Parallel and Concurrent Programming in Haskell, by Simon Marlow. If you are already familiar with concurrent Haskell, just change all the imports from Control.Concurrent.* to Control.Concurrent.Classy.* and fix the type errors.

A brief list of supported functionality:

  • Threads: both unbound and bound.
  • Getting and setting capablities.
  • Yielding and delaying.
  • Mutable state: STM, MVar, and IORef.
  • Atomic compare-and-swap for IORef.
  • Exceptions.
  • All of the data structures in Control.Concurrent.* and Control.Concurrent.STM.* have typeclass-abstracted equivalents.
  • A reimplementation of the async package, providing a higher-level interface over threads, allowing users to conveniently run MonadConc operations asynchronously and wait for their results.

This is quite a rich set of functionality, although it is not complete. If there is something else you need, file an issue!

This used to be part of dejafu, but with the dejafu-0.4.0.0 release, it was split out into its own package.

Why this and not something else?

  • Why not base: like lifted-base, concurrency uses typeclasses to make function types more generic. This automatically eliminates calls to lift in many cases, resulting in clearer and simpler code.

  • Why not lifted-base: fundamentally, lifted-base is still using actual threads and actual mutable variables. When using a concurrency-specific typeclass, this isn’t necessarily the case. The dejafu library provides non-IO-based implementations to allow testing concurrent programs.

  • Why not IOSpec: IOSpec provides many of the operations this library does, however it uses a free monad to do so, which has extra allocation overhead. Furthermore, it does not expose enough of the internals in order to accurately test real-execution semantics, such as relaxed memory.

Contributing

Bug reports, pull requests, and comments are very welcome!

Feel free to contact me on GitHub, through IRC (#haskell on libera.chat), or email ([email protected]).

Changes

Release Notes
=============

This project is versioned according to the PVP_, the *de facto*
standard Haskell versioning scheme.

.. _PVP: https://pvp.haskell.org/


1.11.0.2 (2021-08-15)
---------------------

* Git: :tag:`concurrency-1.11.0.2`
* Hackage: :hackage:`concurrency-1.11.0.2`

Miscellaneous
~~~~~~~~~~~~~

* Remove reference to freenode in README.


1.11.0.1 (2021-03-14)
---------------------

* Git: :tag:`concurrency-1.11.0.1`
* Hackage: :hackage:`concurrency-1.11.0.1`

Fixed
~~~~~

* (:issue:`334`) Compilation error under GHC 9 due to use of
``const``.


1.11.0.0 (2020-05-14)
--------------------

* Git: :tag:`concurrency-1.11.0.0`
* Hackage: :hackage:`concurrency-1.11.0.0`

**Contributors:** :u:`mitchellwrosen` (:pull:`319`).

Added
~~~~~

* (:issue:`316`) ``Control.Monad.Conc.Class.unsafeUnmask``.
* ``Control.Monad.Conc.Class.interruptible``.


1.10.0.0 (2020-05-10)
---------------------

* Git: :tag:`concurrency-1.10.0.0`
* Hackage: :hackage:`concurrency-1.10.0.0`

Added
~~~~~

* (:issue:`312`) ``Control.Monad.Conc.Class.getMaskingState``.


1.9.0.0 (2020-02-26)
--------------------

* Git: :tag:`concurrency-1.9.0.0`
* Hackage: :hackage:`concurrency-1.9.0.0`

Changed
~~~~~~~

* (:issue:`286`) Pulled in changes from :hackage:`stm-2.5.0.0` package:

* Changed ``newTBQueue`` to accept ``Natural`` as a size.
* Changed ``lengthTBQueue`` to return a ``Natural``.


1.8.1.0 (2019-11-16)
--------------------

* Git: :tag:`concurrency-1.8.1.0`
* Hackage: :hackage:`concurrency-1.8.1.0`

Added
~~~~~

* (:issue:`303`) ``Control.Monad.Conc.Class.newTVarConc``, with a
default implementation of ``atomically . newTVar``.


1.8.0.0 (2019-10-04)
--------------------

* Git: :tag:`concurrency-1.8.0.0`
* Hackage: :hackage:`concurrency-1.8.0.0`

Added
~~~~~

* ``MonadFail`` instances for ``Control.Monad.Conc.Class.IsConc`` and
``Control.Monad.STM.IsSTM``.

Changed
~~~~~~~

* Added ``MonadFail`` constraints to
``Control.Concurrent.Classy.QSem.newQSem`` and
``Control.Concurrent.Classy.QSemN.newQSemN``.

Miscellaneous
~~~~~~~~~~~~~

* Fixed a compilation error with GHC 8.8


1.7.0.0 (2019-03-24)
--------------------

* Git: :tag:`concurrency-1.7.0.0`
* Hackage: :hackage:`concurrency-1.7.0.0`

Added
~~~~~

* The ``Control.Monad.Conc.Class.supportsBoundThreads`` function, like
``rtsSupportsBoundThreads`` but returns a monadic result.

Deprecated
~~~~~~~~~~

* ``Control.Monad.Conc.Class.rtsSupportsBoundThreads``, in favour of
``supportsBoundThreads``.


1.6.2.0 (2018-11-28)
--------------------

* Git: :tag:`concurrency-1.6.2.0`
* Hackage: :hackage:`concurrency-1.6.2.0`

**Contributors:** :u:`gip` (:pull:`289`).

Added
~~~~~

* (:pull:`289`) The ``Control.Concurrent.Classy.BoundedChan`` module.
* (:pull:`289`) The ``Control.Concurrent.Classy.Lock`` module.
* (:pull:`289`) The ``Control.Concurrent.Classy.RWLock`` module.


1.6.1.0 (2018-09-23)
--------------------

* Git: :tag:`concurrency-1.6.1.0`
* Hackage: :hackage:`concurrency-1.6.1.0`

Added
~~~~~

* (:issue:`286`) Copy across additions from the :hackage:`stm` package:

* ``Control.Concurrent.Classy.STM.TQueue.flushTQueue``
* ``Control.Concurrent.Classy.STM.TBQueue.flushTBQueue``
* ``Control.Concurrent.Classy.STM.TBQueue.lengthTBQueue``
* ``Control.Concurrent.Classy.STM.TVar.stateTVar``

* (:issue:`287`) The ``Control.Concurrent.Classy.STM.TSem`` module.

Changed
~~~~~~~

* (:issue:`286`) Copy across changes from the :hackage:`stm` package:

* Make definition of ``readTQueue`` consistent with
``readTBQueue``

* Performance improvements to ``peekTQueue`` and ``peekTBQueue``.

Miscellaneous
~~~~~~~~~~~~~

* The upper bound on :hackage:`stm` is <2.6.


1.6.0.0 - IORefs (2018-07-01)
-----------------------------

* Git: :tag:`concurrency-1.6.0.0`
* Hackage: :hackage:`concurrency-1.6.0.0`

Added
~~~~~

* ``Control.Concurrent.Classy.CRef``, deprecated ``*CRef`` functions
and a ``CRef`` alias.

Changed
~~~~~~~

* (:issue:`274`) ``CRef`` is now ``IORef``: all functions, modules,
and types have been renamed.


1.5.0.0 - No More 7.10 (2018-03-28)
-----------------------------------

* Git: :tag:`concurrency-1.5.0.0`
* Hackage: :hackage:`concurrency-1.5.0.0`

Added
~~~~~

* (:issue:`132`) ``forkOSWithUnmask`` in ``MonadConc``

Changed
~~~~~~~

* (:issue:`132`) ``Control.Monad.Conc.Class.fork``, ``forkOn``,
``forkOS``, and ``forkOSN`` are top-level definitions.

Miscellaneous
~~~~~~~~~~~~~

* GHC 7.10 support is dropped. Dependency lower bounds are:

* :hackage:`base`: 4.9
* :hackage:`array`: 0.5.1
* :hackage:`transformers`: 0.5


1.4.0.2 (2018-03-11)
--------------------

* Git: :tag:`concurrency-1.4.0.2`
* Hackage: :hackage:`concurrency-1.4.0.2`

Miscellaneous
~~~~~~~~~~~~~

* (:pull:`245`) The upper bound on :hackage:`exceptions` is <0.11.


1.4.0.1 (2018-02-26)
--------------------

* Git: :tag:`concurrency-1.4.0.1`
* Hackage: :hackage:`concurrency-1.4.0.1`

Miscellaneous
~~~~~~~~~~~~~

* The upper bound on :hackage:`exceptions` is <0.10.


1.4.0.0 (2018-01-19)
--------------------

* Git: :tag:`concurrency-1.4.0.0`
* Hackage: :hackage:`concurrency-1.4.0.0`

Changed
~~~~~~~

* ``Control.Monad.Conc.Class.peekTicket'`` has a more concrete type,
to make deriving newtype instances of ``MonadConc`` possible:

* Old: ``MonadConc m => proxy m -> Ticket m a -> a``
* New: ``MonadConc m => Proxy m -> Ticket m a -> a``


1.3.0.0 - The Bound Thread Release (2017-12-23)
-----------------------------------------------

* Git: :tag:`concurrency-1.3.0.0`
* Hackage: :hackage:`concurrency-1.3.0.0`

**Note:** bound threads are only supported if you compile with GHC and
link with -threaded.

Added
~~~~~

* (:pull:`145`) Bound thread variants of the ``withAsync`` functions:

* ``Control.Concurrent.Classy.Async.asyncBound``
* ``Control.Concurrent.Classy.Async.asyncBoundN``
* ``Control.Concurrent.Classy.Async.withAsyncBound``
* ``Control.Concurrent.Classy.Async.withAsyncBoundN``

* (:pull:`145`) Bound thread functions in ``MonadConc``:

* ``Control.Monad.Conc.Class.forkOS``
* ``Control.Monad.Conc.Class.forkOSN``
* ``Control.Monad.Conc.Class.isCurrentThreadBound``

* (:pull:`145`) Helper functions for bound threads:

* ``Control.Monad.Conc.Class.runInBoundThread``
* ``Control.Monad.Conc.Class.runInUnboundThread``

Changed
~~~~~~~

* (:pull:`145`) ``Control.Monad.Conc.Class.rtsSupportsBoundThreads``
is a re-export from ``Control.Concurrent``.


1.2.3.0 (2017-11-30)
--------------------

* Git: :tag:`concurrency-1.2.3.0`
* Hackage: :hackage:`concurrency-1.2.3.0`

Added
~~~~~

* (:issue:`148`) Named thread variants of the ``withAsync`` functions:

* ``Control.Concurrent.Classy.Async.withAsyncN``
* ``Control.Concurrent.Classy.Async.withAsyncOnN``
* ``Control.Concurrent.Classy.Async.withAsyncWithUnmaskN``
* ``Control.Concurrent.Classy.Async.withAsyncOnWithUnmaskN``


1.2.2.0 (2017-11-05)
--------------------

* Git: :tag:`concurrency-1.2.2.0`
* Hackage: :hackage:`concurrency-1.2.2.0`

Added
~~~~~

* (:issue:`144`) ``IsConc`` and ``IsSTM`` wrapper types:

* ``Control.Monad.Conc.Class.IsConc`` (constructor unexported)
* ``Control.Monad.Conc.Class.toIsConc``
* ``Control.Monad.Conc.Class.fromIsConc``
* ``Control.Monad.STM.Class.IsSTM`` (constructor unexported)
* ``Control.Monad.STM.Class.toIsSTM``
* ``Control.Monad.STM.Class.fromIsSTM``

Changed
~~~~~~~

* ``Control.Monad.Conc.Class.modifyCRefCAS_`` for transformer
instances delegates to the underlying monad, rather than using the
default definition in terms of ``modifyCRefCAS``.


1.2.1.2 (2017-10-14)
--------------------

* Git: :tag:`concurrency-1.2.1.2`
* Hackage: :hackage:`concurrency-1.2.1.2`

Fixed
~~~~~

* (:issue:`134`) ``Control.Monad.Conc.Class.forkWithUnmask`` and
``forkOnWithUnmask`` for the ``IO`` instance does not infinitely
loop (bug introduced in :tag:`concurrency-1.2.1.1`).


1.2.1.1 (2017-10-11)
--------------------

* Git: :tag:`concurrency-1.2.1.1`
* Hackage: :hackage:`concurrency-1.2.1.1`

Changed
~~~~~~~

* Named threads for ``IO`` are implemented with
``GHC.Conc.labelThread``.


1.2.1.0 (2017-10-02)
--------------------

* Git: :tag:`concurrency-1.2.1.0`
* Hackage: :hackage:`concurrency-1.2.1.0`

Added
~~~~~

* (:pull:`125`) Named thread variants of the ``async`` functions:

* ``Control.Concurrent.Classy.Async.asyncN``
* ``Control.Concurrent.Classy.Async.asyncOnN``
* ``Control.Concurrent.Classy.Async.asyncWithUnmaskN``
* ``Control.Concurrent.Classy.Async.asyncOnWithUnmaskN``


1.2.0.0 (2017-09-16)
--------------------

* Git: :tag:`concurrency-1.2.0.0`
* Hackage: :hackage:`concurrency-1.2.0.0`

Changed
~~~~~~~

* ``MonadPlus`` is a superclass of ``MonadSTM``.

* ``Control.Monad.STM.Class.orElse`` is a top-level alias for
``mplus``.

* ``Control.Monad.STM.Class.retry`` is a top-level alias for
``mzero``.


1.1.2.1 (2017-06-07)
--------------------

* Git: :tag:`concurrency-1.1.2.1`
* Hackage: :hackage:`concurrency-1.1.2.1`

Changed
~~~~~~~

* ``Control.Concurrent.Classy.MVar.isEmptyMVar`` does not briefly
empties the ``MVar``, and does not block.


1.1.2.0 (2017-04-05)
--------------------

* Git: :tag:`concurrency-1.1.2.0`
* Hackage: :hackage:`concurrency-1.1.2.0`

Added
~~~~~

* Missing functions copied from :hackage:`async`:

* ``Control.Concurrent.Classy.Async.uninterruptibleCancel``
* ``Control.Concurrent.Classy.Async.replicateConcurrently``
* ``Control.Concurrent.Classy.Async.concurrently_``
* ``Control.Concurrent.Classy.Async.mapConcurrently_``
* ``Control.Concurrent.Classy.Async.forConcurrently_``
* ``Control.Concurrent.Classy.Async.replicateConcurrently_``

* ``Control.Concurrent.Classy.Async.Concurrently`` has a ``Semigroup``
instance when built with :hackage:`base` >= 4.9.

* ``Control.Concurrent.Classy.Async.Concurrently`` has a ``Monoid``
instance.

* ``Control.Monad.Conc.Class`` re-exports
``Control.Monad.Catch.mask_`` and ``uninterruptibleMask_``.

Changed
~~~~~~~

* (:pull:`77`) To match changes in :hackage:`async`,
``Control.Concurrent.Classy.Async.cancel`` and ``withAsync`` block
until the ``Async`` is killed.

Miscellaneous
~~~~~~~~~~~~~

* Every definition, class, and instance now has a Haddock ``@since``
annotation.


1.1.1.0 - The Async Release (2017-03-04)
----------------------------------------

* Git: :tag:`concurrency-1.1.1.0`
* Hackage: :hackage:`concurrency-1.1.1.0`

Added
~~~~~

* The ``Control.Concurrent.Classy.Async`` module.


1.1.0.0 (2017-02-21)
--------------------

* Git: :tag:`concurrency-1.1.0.0`
* Hackage: :hackage:`concurrency-1.1.0.0`

Added
~~~~~

* ``Control.Monad.Conc.Class.tryReadMVar``

Removed
~~~~~~~

* ``Control.Monad.Conc.Class._concMessage``


1.0.0.0 - The Initial Release (2016-09-10)
------------------------------------------

* Git: :tag:`concurrency-1.0.0.0`
* Hackage: :hackage:`concurrency-1.0.0.0`

Added
~~~~~

* Everything.