Hi.
I have some doubts about errno handling in a Concurrent Haskell program.
Let's suppose that GHC non threaded runtime is used, so that each
Haskell thread is bound to an OS thread.
Let's suppose there are two threads running (`A` and `B`).
Thread `A` calls a function `f`, that, in turn, calls via FFI a C
function `c_f`.
Function `c_f` fails, settings errno; however the GHC scheduler suspends
execution of thread `A` and switch to thread `B`, before the current
value of errno is read.
Now, let's suppose thread `B` calls a function `g`, that, in turn, calls
via FFI a C function `c_g`.
Function `c_g`, too, fails, setting errno.
Is this possible?
P.S.:
I have found this is C.Foreign.Error.hs, in base package (not the latest
version):
throwErrnoIfRetry :: (a -> Bool) -> String -> IO a -> IO a
throwErrnoIfRetry pred loc f =
do
res <- f
if pred res
then do
err <- getErrno
if err == eINTR
then throwErrnoIfRetry pred loc f
else throwErrno loc
else return res
This function calls getErrno two times.
Is this safe?
Why the throwErrno function does not accept errno as parameter?
Thanks Manlio Perillo
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
