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Don't exit while a domain is still running. #13190

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merged 2 commits into from
Aug 1, 2024
Merged

Don't exit while a domain is still running. #13190

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Don't exit while a domain is still running
damiendoligez May 22, 2024
e004f57
Add comments to explain the purpose of the test and the need to catch…
damiendoligez May 27, 2024
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16 changes: 14 additions & 2 deletions testsuite/tests/lazy/lazy3.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,17 @@
ocamlopt_flags += " -O3 ";
*)

(* In this test we force a lazy from two concurrent domains without
synchronization. This leads to unspecified behavior but still
should not crash. Currently, the implementation raises Undefined,
and that's what we test here.

Note: due to a bug in the current implementation of
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This comment is likely to go out of sync. When we fix this bug, it is likely that we will not fix this comment as the existing tools (such as running the testsuite) won't help catch this.

My preference should be to remove this Note altogether, with the idea that memory cleanup at exit feature will have a recommendation something to the effect of "When used in a multi-domain program, it is undefined behaviour not to join all the spawned domain before the main domain terminates. Undefined behaviour here includes crashes.".

Additionally, It is not clear what this bug is. If we are keeping this comment in some form, it would be useful to link to the bug report somewhere (or the wip PR #12964).

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This makes sense, so I removed the merge-me label for now. (I am not patient enough to wait for @damiendoligez to update his PR, but then I am not motivated enough to fix the comment myself, so for now let's just wait.)

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I decided to go ahead and merge, and will remove the Note as recommended in trunk.

cleanup-at-exit, we must be careful to join d1 before we exit the
main domain at the end of the program.
*)


let f count =
let _n = (Domain.self ():> int) in
let r = ref 0 in
Expand All @@ -17,11 +28,12 @@ let main () =
let _n = (Domain.self ():> int) in
Lazy.force l)
in
let n2 = Lazy.force l in
let n2 = try Some (Lazy.force l) with Lazy.Undefined -> None in
let n1 = Domain.join d1 in
(n1, n2)

let _ =
match main () with
| (n1, n2) -> Printf.printf "n1=%d n2=%d\n" n1 n2
| (n1, Some n2) -> Printf.printf "n1=%d n2=%d\n" n1 n2
| (_, None) -> print_endline "Undefined"
| exception Lazy.Undefined -> print_endline "Undefined"
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