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 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/

I am having hard time making sense of GHC.Conc. Is there a writeup that describes the significance of "#", or the meaning of "primOp" and "primType"? Thanks Daryoush On Sun, Dec 7, 2008 at 11:48 PM, Don Stewart 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