:: a typeCtrl KGHC 10.0.0.20260917 · lts/ghc-10.0.x · a889611 · 2026-10-18
Moduleconcurrency-1.11.0.3Haskell2010
Multiple-reader, single-writer locks. Used to protect shared resources which may be concurrently read, but only sequentially written.
All functions are exception safe. Throwing asynchronous exceptions will not compromise the internal state of an RWLock. This means it is perfectly safe to kill a thread that is blocking on, for example, acquireRead.
RWLockMultiple-reader, single-writer lock. Is in one of three states:
"Free": Read or write access can be acquired without blocking.
"Read": One or more threads have acquired read access. Blocks write access.
"Write": A single thread has acquired write access. Blocks other threads from acquiring both read and write access.
Create a new RWLock in the "free" state; either read or write access can be acquired without blocking.
Create a new RWLock in the "read" state; only read can be acquired without blocking.
Create a new RWLock in the "write" state; either acquiring read or write will block.
Acquire the read lock.
Blocks if another thread has acquired write access.
If acquireRead terminates without throwing an exception the state of
the RWLock will be "read".
Implementation note: throws an exception when more than maxBound :: Int
Release the read lock.
If the calling thread was the last one to relinquish read access the state will revert to "free".
It is an error to release read access to an RWLock which is not in the "read" state.
A convenience function wich first acquires read access and then performs the computation. When the computation terminates, whether normally or by raising an exception, the read lock is released.
When the state is "write", waitRead blocks until a call to
releaseWrite in another thread changes the state to "free".
When the state is "free" or "read" waitRead returns immediately.
waitRead does not alter the state of the lock.
Note that waitRead is just a convenience function defined as:
waitRead l = mask_ $ acquireRead l >> releaseRead lTry to acquire the read lock; non blocking.
Like acquireRead, but doesn't block. Returns True if the resulting state is "read", False otherwise.
Acquire the write lock.
Blocks if another thread has acquired either read or write access.
If acquireWrite terminates without throwing an exception the state of
the RWLock will be "write".
Release the write lock.
If releaseWrite terminates without throwing an exception the state
will be "free".
It is an error to release write access to an RWLock which is not in the "write" state.
A convenience function wich first acquires write access and then performs the computation. When the computation terminates, whether normally or by raising an exception, the write lock is released.
When the state is "write" or "read" waitWrite blocks until a call
to releaseWrite or releaseRead in another thread changes the state
to "free".
When the state is "free" waitWrite returns immediately.
waitWrite does not alter the state of the lock.
Note that waitWrite is just a convenience function defined as:
waitWrite l = mask_ $ acquireWrite l >> releaseWrite lTry to acquire the write lock; non blocking.
Like acquireWrite, but doesn't block. Returns True if the resulting state is "write", False otherwise.