GH-126910: Revert "Make _Py_get_machine_stack_pointer return the stack pointer (#147945)"

[encukou]

This reverts commit 255026d.

I suspect this commit broke a tier-1 buildbot; I'll use this PR to confirm.
Per PEP-11, any breakage should be fixed or reverted immediately.

• Issue: Supporting stack unwinding in the JIT compiler #126910

[encukou]

!buildbot AMD64.CentOS9.NoGIL

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @encukou for commit 6803150 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F147994%2Fmerge

The command will test the builders whose names match following regular expression: AMD64.CentOS9.NoGIL

The builders matched are:

• AMD64 CentOS9 NoGIL Refleaks PR
• AMD64 CentOS9 NoGIL PR

[encukou]

@Fidget-Spinner @markshannon Are you able to investigate/fix this today?
If not, let's revert so the buildbot can catch other issues, and re-apply later.

[markshannon]

I can't reproduce the failure on either fedora x86-64 or ubuntu Aarch64.

Note, that #147945 doesn't change the way frames are laid out or any aspect of the program, except:

• How JIT frames are laid out (there is no JIT active on the failing buildbot)
• How deep the stack can go before a RecursionError is raised.

Does CentOS have a glibc missing a way to tell the stack size?

I want to try increasing the estimated stack size a bit, as I suspect the combination of debug build, no-gil and perf trampolines is causing the stack to grow very fast.

[markshannon]

#148002

[markshannon]

It doesn't look like it is a stack issue.

It looks like py_trampoline_evaluator isn't calling the generated function for the code object. I don't know why.
It looks like whatever the problem is is being swallowed, not reported:
https://github.com/python/cpython/blob/main/Python/perf_trampoline.c#L452

@pablogsal any idea why py_trampoline_evaluator is not working?

[markshannon]

@encukou go ahead with the revert. I doubt this will be fixed before the weekend

[encukou]

I also can't reproduce on a centos container (on a Fedora kernel).