[Libguestfs] nbdkit | Failed pipeline for master | 9d4b87e0

[Richard W.M. Jones]

On Wed, Jun 21, 2023 at 10:07:34PM +0000, GitLab wrote:
> GitLab
>                ✖ Pipeline #907639365 has failed!
>  
> Project       nbdkit / nbdkit
> Branch        ● master
> Commit        ● 9d4b87e0
>               ocaml: Fix thread registration for OCaml 5 OCa...
> Commit Author ● Richard W.M. Jones
>  
>     Pipeline #907639365 triggered by ●   Richard W.M. Jones
>                        had 9 failed jobs
>                           Failed jobs
> ✖ builds x86_64-fedora-rawhide-clang-prebuilt-env
> ✖ builds    x86_64-almalinux-8-clang-prebuilt-env
> ✖ builds          x86_64-almalinux-8-prebuilt-env
> ✖ builds                         aarch64-macos-12
> ✖ builds      x86_64-centos-stream-8-prebuilt-env
> ✖ builds            x86_64-debian-11-prebuilt-env
> ✖ builds           x86_64-debian-sid-prebuilt-env
> ✖ builds       x86_64-fedora-rawhide-prebuilt-env
> ✖ builds            x86_64-fedora-36-prebuilt-env

Some of these tests are failing in:

  tests/test-shebang-cc-ocaml.sh
  tests/test-cc-ocaml.sh

after the OCaml changes I pushed yesterday, and yes this does appear
to be a genuine problem, but I'm not sure why it happens or how to fix it.

It seems as if the OCaml runtime gets confused after nbdkit forks,
which manifests as a hang here:

https://gitlab.com/nbdkit/nbdkit/-/blob/3e4c1b79a72970c17cb42b21070e61ec634a38bb/plugins/ocaml/plugin.c#L234

OCaml has a mechanism for registering an atfork handler which is
supposed to reinitialize the thread state, but for some reason that
doesn't work or isn't getting called.  Also this mechanism hasn't
changed much in OCaml 5, yet the tests appear to work there (although
it could also be that the mechanism or test is racy, and I only have
one machine with OCaml 5 installed).

Anyway, I will poke again at this later.

Rich.

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