On Thu, Jan 29, 2015 at 5:59 PM, Michael Orlitzky <michael@orlitzky.com> wrote:

and we want to run its test suite. Basically:

* If you run the test suite using runghc, then it works fine.
* If you compile Setup.hs to setup, then the test suite hangs.
* But if you compile Setup.hs to setup using -threaded, it works?

IIRC bytecode (runghc, ghci) always uses the threaded runtime, and this problem can be a symptom of an FFI call that can block but wasn't declared as potentially blocking; so the runtime calls it expecting it to not block and the program freezes when it does block. In the threaded runtime, other OS threads can continue executing in this case; in the non-threaded runtime, this will block the "green" thread scheduler.

brandon s allbery kf8nh sine nomine associates

allbery.b@gmail.com ballbery@sinenomine.net

unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net