I'm trying to write a function (run_guarded) that takes another function (f), and runs it for some amount of time. If f terminates with value x, then the result of run_guarded should be Some x, otherwise it should be None. Here's my implementation using the Thread library:
let run_guarded f x =
let res = ref None in
let m = Mutex.create () in
let c = Condition.create () in
let _ = Mutex.lock m in
let tid1 = Thread.create (fun x ->
let z = f x in
let _ = res := Some z in
let _ = Mutex.lock m in
let _ = Mutex.unlock m in
let _ = Condition.broadcast c in
()) x
and tid2 = Thread.create (fun () ->
let _ = Thread.delay 0.3 in
let _ = Mutex.lock m in
let _ = Mutex.unlock m in
let _ = Condition.broadcast c in
()) ()
in
let _ = Condition.wait c m in
let _ = Mutex.unlock m in
let _ = try Thread.kill tid2 with _ -> () in
let _ = try Thread.kill tid1 with _ -> () in
!res
It seems like it should work, but it doesn't work if the function f doesn't terminate. It seems to be running everything serially. I know that threads aren't actually parallel, but I thought they were preemptive in which case it seems like this should work. Does anyone know what I did wrong here?
Thank you very much.