[Haskell-cafe] Why does sleep not work?

[George Pollard]

On Wed, 2009-02-11 at 01:50 +0100, Manlio Perillo wrote:
> George Pollard ha scritto:
> > [...]
> >
> >> So, it seems nanosleep get interruped by a signal.
> > 
> > This works:
> > 
> >> import System.Posix
> >>
> >> main = do
> >> 	putStrLn "Waiting for 5 seconds."
> >> 	blockSignals $ addSignal sigVTALRM emptySignalSet
> >> 	sleep 5
> >> 	putStrLn "Done."
> >>
> > So (see my earlier email) `sleep` is lying about what interrupts it :)
> > 
> > - George
> 
> 
> A possibly better solution is:
> 
> sleep' :: Int -> IO Int
> sleep' n = do
>    n' <- sleep n
>    if n' == 0 then return 0 else sleep' n'
> 
> 
>  From the trace, I see that nanosleep is being called 17 times here.
> 
> Another solution is to set RTS flag:
> ./bug_sleep +RTS -V0 -RTS
> 
> 
> What strange is that the timer is created in non threaded RTS, too, but 
> sleep is interrupted only with the threaded RTS.
> 
> This may be caused by an "incorrect" execution of a foreign function 
> marked safe.

I just realized that  for some reason I thought that `sleep` reported
the signal that interrupted it... contrary to the documentation... as
such, several of my replies to this thread may read as non-sequiturs :P
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