posix shutdown investigation/hacks [take 2]

[julianoes]

This PR is on top of #11525.

For me Ctrl+C and shutdown work on both Linux and Windows. Please cross-test and review.

I tried to get rid of all pthread_cancel so that one workaround in the lockstep scheduler can removed:
https://github.com/PX4/Firmware/blob/2ebb9d2ab52bce56a74d34d3b36c7130422577c2/platforms/posix/src/lockstep_scheduler/include/lockstep_scheduler/lockstep_scheduler.h#L24-L34

[julianoes]

@dagar I don't understand the path for this dyn test. It now works locally but still seems to fail for appveyor! 😞

[MaEtUgR]

Nice, thanks @julianoes! and @dagar for starting out 👍

• The shutdown command now works again on Windows.

• Just wanted to mention it prints two times Shutting down:

  pxh> shutdown
  Shutting down
  pxh> Shutting down
  
  $
  

  which is no problem at all.

• Note that Ctrl+C still hangs on Windows and waits for an enter before exiting with the SIGINT callback attached
  https://github.com/PX4/Firmware/blob/b54ca67de9b5900c7ed11bef323c7b4e5a0339b6/platforms/posix/src/main.cpp#L410-L416

  So we cannot get rid of that one yet. But I think that's a different smaller problem which was there before. Maybe I can solve that one.

[julianoes]

@MaEtUgR hm, so why did Ctrl+C work for me on Windows (Cygwin)?

[MaEtUgR]

@MaEtUgR hm, so why did Ctrl+C work for me on Windows (Cygwin)?

Ctrl+C still works because of the lines I added in #11305 and referenced above. This pr is fine and fixes the shutdown command but just does not yet allow to remove the hotfix for Ctrl+C.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.

[MaEtUgR]

We should have got this in before it had that many conflicts... @julianoes any plans to rebase (without any pressure)?

[julianoes]

@MaEtUgR yes we should get this in 😄 but it's far down my list.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.

[julianoes]

Impossible to rebase, closing.