| Safe Haskell | None |
|---|
Data.Atomics
Contents
Description
Provides atomic memory operations on IORefs and Mutable Arrays.
Pointer equality need not be maintained by a Haskell compiler. For example, Int
values will frequently be boxed and unboxed, changing the pointer identity of
the thunk. To deal with this, the compare-and-swap (CAS) approach used in this
module is uses a sealed representation of pointers into the Haskell heap
(Tickets). Currently, the user cannot coin new tickets, rather a Ticket
provides evidence of a past observation, and grants permission to make a future
change.
- type Ticket a = Any a
- peekTicket :: Ticket a -> a
- casArrayElem :: MutableArray RealWorld a -> Int -> Ticket a -> a -> IO (Bool, Ticket a)
- casArrayElem2 :: MutableArray RealWorld a -> Int -> Ticket a -> Ticket a -> IO (Bool, Ticket a)
- readArrayElem :: forall a. MutableArray RealWorld a -> Int -> IO (Ticket a)
- casByteArrayInt :: MutableByteArray RealWorld -> Int -> Int -> Int -> IO Int
- fetchAddByteArrayInt :: MutableByteArray RealWorld -> Int -> Int -> IO Int
- readForCAS :: IORef a -> IO (Ticket a)
- casIORef :: IORef a -> Ticket a -> a -> IO (Bool, Ticket a)
- casIORef2 :: IORef a -> Ticket a -> Ticket a -> IO (Bool, Ticket a)
- readMutVarForCAS :: MutVar# RealWorld a -> IO (Ticket a)
- casMutVar :: MutVar# RealWorld a -> Ticket a -> a -> IO (Bool, Ticket a)
- casMutVar2 :: MutVar# RealWorld a -> Ticket a -> Ticket a -> IO (Bool, Ticket a)
- storeLoadBarrier :: IO ()
- loadLoadBarrier :: IO ()
- writeBarrier :: IO ()
Types for atomic operations
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.
peekTicket :: Ticket a -> aSource
A ticket contains or can get the usable Haskell value.
Atomic operations on mutable arrays
casArrayElem :: MutableArray RealWorld a -> Int -> Ticket a -> a -> IO (Bool, Ticket a)Source
Compare-and-swap
casArrayElem2 :: MutableArray RealWorld a -> Int -> Ticket a -> Ticket a -> IO (Bool, Ticket a)Source
This variant takes two tickets: the new value is a ticket rather than an
arbitrary, lifted, Haskell value.
readArrayElem :: forall a. MutableArray RealWorld a -> Int -> IO (Ticket a)Source
Atomic operations on byte arrays
casByteArrayInt :: MutableByteArray RealWorld -> Int -> Int -> Int -> IO IntSource
fetchAddByteArrayInt :: MutableByteArray RealWorld -> Int -> Int -> IO IntSource
Atomic operations on IORefs
readForCAS :: IORef a -> IO (Ticket a)Source
Arguments
| :: IORef a | The |
| -> Ticket a | A ticket for the |
| -> a | The |
| -> IO (Bool, Ticket a) |
Performs a machine-level compare and swap operation on an
IORef. Returns a tuple containing a Bool which is True when a
swap is performed, along with the current value from the IORef.
Note "compare" here means pointer equality in the sense of
reallyUnsafePtrEquality#.
Arguments
| :: IORef a | |
| -> Ticket a | A ticket for the |
| -> Ticket a | A ticket for the |
| -> IO (Bool, Ticket a) |
This variant takes two tickets, i.e. the new value is a ticket rather than an
arbitrary, lifted, Haskell value.
Atomic operations on raw MutVars
readMutVarForCAS :: MutVar# RealWorld a -> IO (Ticket a)Source
casMutVar :: MutVar# RealWorld a -> Ticket a -> a -> IO (Bool, Ticket a)Source
MutVar counterpart of casIORef.
casMutVar2 :: MutVar# RealWorld a -> Ticket a -> Ticket a -> IO (Bool, Ticket a)Source
This variant takes two tickets, i.e. the new value is a ticket rather than an
arbitrary, lifted, Haskell value.
Memory barriers
storeLoadBarrier :: IO ()Source
Memory barrier implemented by the GHC rts (SMP.h).
loadLoadBarrier :: IO ()Source
Memory barrier implemented by the GHC rts (SMP.h).
writeBarrier :: IO ()Source
Memory barrier implemented by the GHC rts (SMP.h).