gh-137884: Added threading.get_native_id on Illumos/Solaris

[yuce]

Fixes: #137884

This PR enables threading.get_native_id on Illumos distributions and Solaris.

Illumos/Solaris defines the thr_self function which returns the thread ID, unique for the process:
https://docs.oracle.com/cd/E36784_01/html/E36874/thr-self-3c.html
On OmniOS and Solaris, thr_self returns the thread IDs from 1, incrementing it for each thread.
Since it is not unique in the system, it is not usable by itself per Python doc:
https://docs.python.org/3/library/threading.html#threading.get_native_id

get_native_id() -> integer
Return a non-negative integer identifying the thread as reported
by the OS (kernel). This may be used to uniquely identify a
particular thread within a system.

In order to make it unique within the system, I put the PID from getpid in the higher 4 bytes, and thread ID from thr_self in the lower 4 bytes of the returned unsigned long.

getpid doesn't return an error value, and it returns pid_t which is 4 bytes (int) on Illumos/Solaris:
https://docs.oracle.com/cd/E23824_01/html/821-1463/getpid-2.html

thr_self doesn't return an error value, and it returns thread_t which is 4 bytes (unsigned int) on Illumos/Solaris:
https://docs.oracle.com/cd/E36784_01/html/E36874/thr-self-3c.html

With the changes in this PR, test_native_id_after_fork in Lib/test/test_threading.py passes, which was skipped before.
This PR does not introduce any new test faliures.

• Issue: Illumos and Solaris Thread Native ID #137884

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[auvipy]

shouldn't we also try extra test for this the change?

[yuce]

@auvipy

shouldn't we also try extra test for this the change?

Could you explain that a bit?
Do you have a specific test in mind?

[serhiy-storchaka]

LGTM. 👍

[ZeroIntensity]

shouldn't we also try extra test for this the change?

test_threading already tests for this. The tests for threading.get_native_id are protected by a hasattr, so if a new system gets support for it, that hasattr now passes and runs the test.

Unfortunately, we don't have any working Solaris buildbots to confirm that those tests actually pass now.

[serhiy-storchaka]

I tested on OpenIndiana.