Alex Willmer

For completeness, what is the OS and Python version on the affected machines?

Notes to self > `pselect6(1, [0], NULL, NULL, NULL, NULL) = 1 (in [0])` pselect6() asked if a single fd (fd=0) was ready to read (such that read() would not...

Brainstorming possibilities (with [input from claude.ai](https://claude.ai/share/ac2d4e3f-c7d5-4bb0-bd31-cdb5dc24c464)), in roughly decending order of likelyhood by my gut feeling 1. EOF - remote end of pipe/socket that feeds fd=0 closed, or was reset...

> 1. EOF - remote end of pipe/socket that feeds fd=0 closed, or was reset If this is the case, does the parent notice? Does it do anything about it?...

Rather than diagnose/fix the exact cause, fixing the symptom may be more robust. E.g. have the first stage self-destruct if it hasn't reached the second stage within N seconds.

> Yeah, the [synchronous call](https://github.com/mitogen-hq/mitogen/commit/85d6046f2fbf4e80c472f7a06596bf8ad1fcd9e6#diff-0db6f9348a3e446380cf34f9d57daae2f2d55e007f5f7eac2aae40ebe3d2d526L1444) prior to [#1307](https://github.com/mitogen-hq/mitogen/pull/1307) did not had this issue. So something with the new way of reading the data fails where the previous detected that case!...

Please could you try https://github.com/mitogen-hq/mitogen/commit/9cc0ab0823b0280f5309d0f102a42f2cceb99b57, from #1349

> `&yellow 0.0h 1.2h 1100427 root /usr/bin/python3( mitogen:user@host:668520)` All the yellow (ide processes) are fork parents with argv `/path/to/python()` - they've `exec()`d a fresh Python, and it is waiting for...

> I was not able to reproduce anymore busy looping (red) processes using [9cc0ab0](https://github.com/mitogen-hq/mitogen/commit/9cc0ab0823b0280f5309d0f102a42f2cceb99b57), from [#1349](https://github.com/mitogen-hq/mitogen/pull/1349) cherry picked on top of most recent master [fdb5c62](https://github.com/mitogen-hq/mitogen/commit/fdb5c625324e941d867961c41c83e0bfc64db31f). I don't think you can...

@DanielRaapDev did you try the branch for #1349? (HEAD was [9cc0ab0](https://github.com/mitogen-hq/mitogen/commit/9cc0ab0823b0280f5309d0f102a42f2cceb99b57), now [03a0a15](https://github.com/mitogen-hq/mitogen/pull/1349/commits/03a0a151ff004959abbdff0b15d21cc3266dd960))