Re: [Haskell-cafe] Race condition possible?

bugfact:

Consider the following code

stamp v x = do t <- getCurrentTime putMVar v (x,t)

Is it possible - with GHC - that a thread switch happens after the t <- getCurrentTime and the putMVar v (x,t)?

Yes. if 't' is heap allocated, there could be a context switch.

If so, how would it be possible to make sure that the operation of reading the current time and writing the pair to the MVar is an "atomic" operation, in the sense that no thread switch can happen between the two? Would this require STM?

Using 'atomically' and TVars in STM, perhaps? Else, use withMVar? Or a modifyMVar in IO? -- Don