In CPython, we store (persistent) runtime data in several locations. (See https://github.com/ericsnowcurrently/multi-core-python/wiki/3-CPython's-Runtime#cpythons-run-time-data.)

The state of each interpreter (PyInterpreterState) encapsulates the data which is unique to that interpreter and isolated from other interpreters. That isolation is important for the proper operation of multiple interpreters in a process, and will be critical for a per-interpreter GIL, AKA PEP 684 (assuming it gets approved). There are still a number of gaps in isolation which we will address here.

The deficiencies may be categorized by the following:

• shared runtime state (_PyRuntimeState) conceptually better suited to each interpreter
• shared runtime state currently protected by the GIL
• shared global variables that shouldn't be shared
• shared global variables currently protected by the GIL

Linked PRs

• gh-100227: Port dup3_works to the module state variable. #100262
• gh-100227: Isolate the Import State to Each Interpreter #101941
• gh-100227: Move the dtoa State to PyInterpreterState #102331
• gh-100227: Move _str_replace_inf to PyInterpreterState #102333
• gh-100227: Move func_state.next_version to PyInterpreterState #102334
• gh-100227: Move next_keys_version to PyInterpreterState #102335
• gh-100227: Move dict_state.global_version to PyInterpreterState #102338
• gh-100227: Move the Dict of Interned Strings to PyInterpreterState #102339
• GH-100227: cleanup initialization of global interned dict #102682
• gh-100227: Make the Global Interned Dict Safe for Isolated Interpreters #102858
• gh-100227: Make the Global Interned Dict Safe for Isolated Interpreters #102925
• gh-100227: Make the Global PyModuleDef Cache Safe for Isolated Interpreters #102938
• gh-100227: Revert "gh-100227: Make the Global Interned Dict Safe for Isolated Interpreters (gh-102925)" #103063
• gh-100227: Make the Global PyModuleDef Cache Safe for Isolated Interpreters #103084
• gh-100227: Fix Cleanup of the Extensions Cache #103150
• gh-100227: Use an Array for _PyRuntime's Set of Locks During Init #103315
• gh-100227: Add a Granular Lock for _PyRuntime.imports.extensions.dict #103460
• gh-100227: Only Use deepfreeze for the Main Interpreter #103794
• gh-100227: Add Missing Locks for Specific Global Runtime State #105470
• gh-100227: Lock Around Use of the Global "atexit" State #105514
• gh-100227: Lock Around Adding Global Audit Hooks #105515
• gh-100227: Lock Around Modification of the Global Allocators State #105516
• [3.12] gh-100227: Lock Around Use of the Global "atexit" State (gh-105514) #105517
• [3.12] gh-100227: Lock Around Adding Global Audit Hooks (gh-105515) #105525
• [3.12] gh-100227: Lock Around Modification of the Global Allocators State (gh-105516) #105532
• gh-105766: Add Locking Around Custom Allocators #105619