[ocaml5-issue] Deadlock in Dynlink test on Cygwin+MinGW+MSVC

[shym]

Deadlock observed in a run on trunk Cygwin:
https://github.com/shym/multicoretests/actions/runs/4367430739/jobs/7638729550#step:21:764

Wed, 08 Mar 2023 22:46:19 GMT random seed: 366632243
Wed, 08 Mar 2023 22:46:19 GMT generated error fail pass / total     time test name
Wed, 08 Mar 2023 22:46:19 GMT
Wed, 08 Mar 2023 22:46:19 GMT [ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain
Wed, 08 Mar 2023 22:47:55 GMT [ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain (generating)
Wed, 08 Mar 2023 22:49:08 GMT [ ]    0    0    0    0 /  100    96.0s negative Lin DSL Dynlink test with Domain (shrinking:    1)
Thu, 09 Mar 2023 00:38:34 GMT [ ]    0    0    0    0 /  100   168.9s negative Lin DSL Dynlink test with Domain (shrinking:    3)
Thu, 09 Mar 2023 00:38:34 GMT Error: The operation was canceled.

As the code paths are completely different between Cygwin (which provides a dlopen()) and Windows (which uses flexdll), this is probably not related to #290.

[dra27]

Ah - actually, we do still use flexdll on Cygwin, so I expect this is related.

[shym]

Another point of interest, related but maybe involving something else: the Dynlink test on Cygwin can end up abruptly (like a segfault) but reporting no error ($? is 0). There might be another issue there, in the way some errors get dropped? 🤔

[jmid]

We are seeing several Cygwin timeouts during Dynlink, which may well be this bug being triggered

• https://github.com/ocaml-multicore/multicoretests/actions/runs/6049285277/job/16416279067 5.1
• https://github.com/ocaml-multicore/multicoretests/actions/runs/5950931125/job/16139719760 5.1
• https://github.com/ocaml-multicore/multicoretests/actions/runs/5942185755/job/16114588868 5.1
• https://github.com/ocaml-multicore/multicoretests/actions/runs/6042013562/job/16396215009 trunk

[jmid]

Seen again on Cygwin 5.1.0~rc2 when merging #389 into main
https://github.com/ocaml-multicore/multicoretests/actions/runs/6077015167/job/16485985404

random seed: 153981
generated error fail pass / total     time test name

[ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain
[ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain (generating)
Error: The operation was canceled.

[jmid]

This triggered again on the 0.3 branch for Cygwin trunk part1
https://github.com/ocaml-multicore/multicoretests/actions/runs/6481561492/job/17599326796

random seed: 406303381
generated error fail pass / total     time test name

[ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain
[ ]    0    0    0    0 /  100     0.0s negative Lin DSL Dynlink test with Domain (generating)
Error: The operation was canceled.