Data.Columbia.DualLock

A dual lock can be taken in either exclusive or shared mode, and also supports switching (atomically) from one mode to the other.

Documentation

data DualLockShared

Constructors

DualLockShared !FilePath !FileLock !FileLock

data DualLock

Constructors

DualLock !FilePath !FileLock !FileLock

dualLockShared :: FilePath -> IO DualLockShared

dualLock :: FilePath -> IO DualLock

unlockShared :: DualLockShared -> IO ()

unlock :: DualLock -> IO ()

switchLocks :: DualLockShared -> IO DualLock

N.B. That two simultaneous attempts to switch locks will deadlock. Please protect a critical section that switches locks with some other lock, to ensure this doesn't happen. For instance, the garbage collector protects its use of switchLocks on a dual lock, with an exclusive writer lock.

switchLocks2 :: DualLock -> IO DualLockShared

Switching from an exclusive to a shared lock may be done at any time.