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Add ?cloexec parameter to Lwt_unix functions that create file descriptors #327

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mfp opened this issue Mar 26, 2017 · 1 comment · Fixed by #901
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Add ?cloexec parameter to Lwt_unix functions that create file descriptors #327

mfp opened this issue Mar 26, 2017 · 1 comment · Fixed by #901
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4.2.2

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@mfp
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mfp commented Mar 26, 2017

OCaml 4.05 adds an optional cloexec parameter to several Unix functions, allowing the close-on-exec flag to be set as the operation is performed atomically on some platforms (limited to Linux atm.) -- otherwise there's a race condition when there are multiple (system) threads.

These functions would be affected: Lwt_unix.dup, dup2, pipe, socket, socketpair, accept.
Other functions that build on them and could also take ?cloexec: accept_n, pipe_in, pipe_out.
@mfp mfp mentioned this issue Mar 26, 2017
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@aantron aantron added the medium label May 20, 2017
@aantron aantron added this to the 4.2.2 milestone Jul 27, 2019
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aantron commented Aug 3, 2019

I'm closing this issue for now, because:

  • The issue with multiple threads is probably less likely in typical Lwt programs, than even in programs using only Unix.
  • We haven't had any reports of a problem due to this.

We can reopen and fix later, if necessary.

Here's a link to text about the issue in module Unix: https://caml.inria.fr/pub/docs/manual-ocaml/libref/Unix.html#VALset_close_on_exec.

@aantron aantron closed this as completed Aug 3, 2019
@vog vog mentioned this issue Jul 24, 2021
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MisterDA added a commit to MisterDA/lwt that referenced this issue Nov 9, 2021
@MisterDA
Add ?cloexec:bool argument to wrapped Unix functions in Lwt_unix
0c0a13e 
In the Lwt_unix module, add `?cloexec:bool` optional arguments to
functions that create file descriptors (`dup`, `dup2`, `pipe`,
`pipe_in`, `pipe_out`, `socket`, `socketpair`, `accept`, `accept_n`).
The `?cloexec` argument is simply forwarded to the wrapped Unix
function (with OCaml >= 4.05, see [ocaml/ocaml#650][650]), or emulated
as best-effort with `Unix.set_close_on_exec` on older OCaml versions.

Fix ocsigen#327. Fix ocsigen#847. See also ocsigen#872.

[650]: ocaml/ocaml#650
@MisterDA MisterDA mentioned this issue Nov 9, 2021
Merged
smorimoto pushed a commit to raphael-proust/lwt that referenced this issue Dec 2, 2021
@MisterDA @smorimoto
Add ?cloexec:bool argument to wrapped Unix functions in Lwt_unix
3f12585 
In the Lwt_unix module, add `?cloexec:bool` optional arguments to
functions that create file descriptors (`dup`, `dup2`, `pipe`,
`pipe_in`, `pipe_out`, `socket`, `socketpair`, `accept`, `accept_n`).
The `?cloexec` argument is simply forwarded to the wrapped Unix
function (with OCaml >= 4.05, see [ocaml/ocaml#650][650]), or emulated
as best-effort with `Unix.set_close_on_exec` on older OCaml versions.

Fix ocsigen#327. Fix ocsigen#847. See also ocsigen#872.

[650]: ocaml/ocaml#650
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Add ?cloexec:bool argument to wrapped Unix functions in Lwt_unix MisterDA/lwt
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