Description
Feature or enhancement
The --disable-gil builds occasionally need to pause all but one thread. Some examples include:
- Cyclic garbage collection, where this is often called a "stop the world event"
- Before calling
fork(), to ensure a consistent state for internal data structures - During interpreter shutdown, to ensure that daemon threads aren't accessing Python objects
In the nogil-3.12 fork, a stop-the-world call paused all threads in all interpreters. In CPython 3.13, we probably want to provide two levels of "stop-the-world": per-interpreter and global. In general, per-interpreter pauses are preferable to global pauses, but there are some cases (like before fork()) where want all threads to pause, so that we don't fork() while a thread is modifying some global runtime structure.
In the default build, stop-the-world calls should generally be no-ops, but global pauses may be useful in a few cases, such as before fork() when using multiple interpreters each with their own "GIL".
In the nogil-3.12 fork, this was implemented together with other GC modifications: colesbury/nogil-3.12@2864b6b36e. I'd like to implement it separately in 3.13 to keep the PRs smaller.