…t to be reused (gh-121428)

…ead (#121572)

)

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>

Export the PySignal_SetWakeupFd() function. Previously, the function
was documented but it couldn't be used in 3rd party code.

On heavily loaded machines, the subprocess may finish its sleep before
the parent process manages to synchronize with it via a failed lock.

This leads to errors like:

  Exception: failed to sync child in 300.3 sec

Use pipes instead to mutually synchronize between parent and child.

…nctions (#121538)

`munmap(NULL)` is not noop, like `free(NULL)` is.

Fixes an observed testsuite hang on 32-bit ARM systems.

…ld (GH-120672)

The only remaining race in dictobject.c was in _PyDict_CheckConsistency
when the dictionary has shared keys.

The functions look thread-safe and I haven't seen any warnings issued
when running the tests locally.

This fixes a mistake in gh-113012 and adds a test that verifies the fix.

Co-authored-by: Erlend E. Aasland <erlend@python.org>

…121451)