[Haskell-cafe] what does "atomically#" mean?

[Ryan Ingram]

That code is in <ghc root>/rts/STM.c

  -- ryan

2009/1/30 Daryoush Mehrtash <dmehrtash at gmail.com>:
> I like to look at the code where the runtime detects a TVar, inside an
> atomic block, has been changed by another thread and hence it  aborts the
> atomic operation.  Any suggestion as to where I would find the code?
>
> daryoush
>
> On Sun, Dec 7, 2008 at 10:48 PM, Don Stewart <dons at galois.com> wrote:
>>
>> dmehrtash:
>> >    Any idea was the atomically# mean in the following code?
>> >
>> >    atomically :: STM a -> IO a
>> >    atomically (STM m) = IO (\s -> (atomically# m) s )
>> >
>> >    Code is from GHC.Conc module
>> >
>> >  [1]http://www.haskell.org/ghc/docs/6.6/html/libraries/base/GHC-Conc.html
>>
>> It is a primitive hook into the runtime, where transactional memory is
>> implemented.
>>
>> It is documented in the primops module in the GHC source,
>>
>>    $ cd ghc/compiler/prelude/
>>
>>
>>  ------------------------------------------------------------------------
>>    section "STM-accessible Mutable Variables"
>>
>>  ------------------------------------------------------------------------
>>
>>    primtype TVar# s a
>>
>>    primop  AtomicallyOp "atomically#" GenPrimOp
>>          (State# RealWorld -> (# State# RealWorld, a #) )
>>       -> State# RealWorld -> (# State# RealWorld, a #)
>>       with
>>       out_of_line = True
>>       has_side_effects = True
>>
>>    primop  RetryOp "retry#" GenPrimOp
>>       State# RealWorld -> (# State# RealWorld, a #)
>>       with
>>       out_of_line = True
>>       has_side_effects = True
>>
>>
>> Along with other primitives like:
>>
>> ------------------------------------------------------------------------
>> section "Parallelism"
>> ------------------------------------------------------------------------
>>
>>    primop  ParOp "par#" GenPrimOp
>>       a -> Int#
>>       with
>>          -- Note that Par is lazy to avoid that the sparked thing
>>          -- gets evaluted strictly, which it should *not* be
>>       has_side_effects = True
>>
>> -- Don
>
>
>
> --
> Daryoush
>
> Weblog:  http://perlustration.blogspot.com/
>
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