Editing Lightweight concurrency (section)

=== Proposal ===

The new, scheduler agnostic version of takeMVar (say takeMVarPrim), will have the type:

<haskell>
takeMVarPrim :: PTM () -> PTM () -> MVarPrim a -> IO a
</haskell>

where the first and second arguments are the block and unblock actions. If the blocking and unblocking actions are known, takeMVar with its usual type can be obtained simply by partial application:

<haskell>
takeMVar :: MVarPrim a -> IO a
takeMVar = takeMVarPrim blockAct unblockAct
</haskell>

Since the MVar implementation is independent of the schedulers, even threads from different schedulers can perform operations on the same MVar. The knowledge of schedulers is completely embedded in the block and unblock actions. Block and unblock actions can be obtained from [[Lightweight_concurrency#Up-call_handlers|up-call handlers]].