Synchronising, strict variables
Values placed in an MVar are evaluated to weak-head normal form
before being placed in the MVar, preventing a common source of
space-leaks involving synchronising variables.
|Create an MVar which contains the supplied value.
Put a value into an MVar. If the MVar is currently full,
putMVar will wait until it becomes empty.
There are two further important properties of putMVar:
- putMVar is single-wakeup. That is, if there are multiple
threads blocked in putMVar, and the MVar becomes empty,
only one thread will be woken up. The runtime guarantees that
the woken thread completes its putMVar operation.
- When multiple threads are blocked on an MVar, they are
woken up in FIFO order. This is useful for providing
fairness properties of abstractions built using MVars.
|This is a combination of takeMVar and putMVar; ie. it takes the value
from the MVar, puts it back, and also returns it.
|Take a value from an MVar, put a new value into the MVar and
return the value taken. Note that there is a race condition whereby
another process can put something in the MVar after the take
happens but before the put does.
|A non-blocking version of putMVar. The tryPutMVar function
attempts to put the value a into the MVar, returning True if
it was successful, or False otherwise.
|withMVar is a safe wrapper for operating on the contents of an
MVar. This operation is exception-safe: it will replace the
original contents of the MVar if an exception is raised (see
|A safe wrapper for modifying the contents of an MVar. Like withMVar,
modifyMVar will replace the original contents of the MVar if an
exception is raised during the operation.
|A slight variation on modifyMVar_ that allows a value to be
returned (b) in addition to the modified value of the MVar.
|Produced by Haddock version 2.4.2|