base-4.18.1.0: Basic libraries

Copyright | (c) The University of Glasgow 1994-2002
License | see libraries/base/LICENSE
Maintainer | cvs-ghc@haskell.org
Stability | internal
Portability | non-portable (GHC extensions)
Safe Haskell | Trustworthy
Language | Haskell2010

GHC.Conc.IO

Contents

- Waiting

Description

Basic concurrency stuff.

Synopsis

- ensureIOManagerIsRunning :: IO ()
- ioManagerCapabilitiesChanged :: IO ()
- interruptIOManager :: IO ()
- threadDelay :: Int -> IO ()
- registerDelay :: Int -> IO (TVar Bool)
- threadWaitRead :: Fd -> IO ()
- threadWaitWrite :: Fd -> IO ()
- threadWaitReadSTM :: Fd -> IO (STM (), IO ())
- threadWaitWriteSTM :: Fd -> IO (STM (), IO ())
- closeFdWith :: (Fd -> IO ()) -> Fd -> IO ()

# Documentation

ensureIOManagerIsRunning :: IO () Source #

ioManagerCapabilitiesChanged :: IO () Source #

interruptIOManager :: IO () Source #

Interrupts the current wait of the I/O manager if it is currently blocked. This instructs it to re-read how much it should wait and to process any pending events.

Since: base-4.15

# Waiting

threadDelay :: Int -> IO () Source #

Suspends the current thread for a given number of microseconds (GHC only).

There is no guarantee that the thread will be rescheduled promptly when the delay has expired, but the thread will never continue to run earlier than specified.

Be careful not to exceed `maxBound :: Int`, which on 32-bit machines is only 2147483647 μs, less than 36 minutes. Consider using `Control.Concurrent.Thread.Delay.delay` from `unbounded-delays` package.

registerDelay :: Int -> IO (TVar Bool) Source #

Switch the value of returned `TVar` from initial value `False` to `True` after a given number of microseconds. The caveats associated with `threadDelay` also apply.

Be careful not to exceed `maxBound :: Int`, which on 32-bit machines is only 2147483647 μs, less than 36 minutes.

threadWaitRead :: Fd -> IO () Source #

Block the current thread until data is available to read on the given file descriptor (GHC only).

This will throw an `IOError` if the file descriptor was closed while this thread was blocked. To safely close a file descriptor that has been used with `threadWaitRead`, use `closeFdWith`.

threadWaitWrite :: Fd -> IO () Source #

Block the current thread until data can be written to the given file descriptor (GHC only).

This will throw an `IOError` if the file descriptor was closed while this thread was blocked. To safely close a file descriptor that has been used with `threadWaitWrite`, use `closeFdWith`.

threadWaitReadSTM :: Fd -> IO (STM (), IO ()) Source #

Returns an STM action that can be used to wait for data to read from a file descriptor. The second returned value is an IO action that can be used to deregister interest in the file descriptor.

threadWaitWriteSTM :: Fd -> IO (STM (), IO ()) Source #

Returns an STM action that can be used to wait until data can be written to a file descriptor. The second returned value is an IO action that can be used to deregister interest in the file descriptor.

closeFdWith Source #

Arguments

:: (Fd -> IO ()) | Low-level action that performs the real close.
-> Fd | File descriptor to close.
-> IO () |

Close a file descriptor in a concurrency-safe way (GHC only). If you are using `threadWaitRead` or `threadWaitWrite` to perform blocking I/O, you must use this function to close file descriptors, or blocked threads may not be woken.

Any threads that are blocked on the file descriptor via `threadWaitRead` or `threadWaitWrite` will be unblocked by having IO exceptions thrown.