Data.Queue.Instances
Documentation
data MVar a
An MVar (pronounced "em-var") is a synchronising variable, used
for communication between concurrent threads. It can be thought of
as a a box, which may be empty or full.
data STM a
A monad supporting atomic memory transactions.
data TMVar a
A TMVar is a synchronising variable, used
for communication between concurrent threads. It can be thought of
as a box, which may be empty or full.
atomically :: STM a -> IO a
Perform a series of STM actions atomically.
You cannot use atomically inside an unsafePerformIO or unsafeInterleaveIO.
Any attempt to do so will result in a runtime error. (Reason: allowing
this would effectively allow a transaction inside a transaction, depending
on exactly when the thunk is evaluated.)
However, see newTVarIO, which can be called inside unsafePerformIO,
and which allows top-level TVars to be allocated.