gh-111964: Implement stop-the-world pauses by colesbury · Pull Request #112471

gh-111964: Implement stop-the-world pauses by colesbury · Pull Request #112471 · python/cpython

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

This adds the following functions to implement global and per-interpreter pauses:

* `_PyRuntimeState_StopTheWorld` and `_PyRuntimeState_StartTheWorld`
* `_PyInterpreterState_StopTheWorld` and `_PyInterpreterState_StartTheWorld`

These functions are no-ops outside of the `--disable-gil` build.

This also adds `_PyRWMutex`, a "readers-writer" lock, which is used to
serialize global stop-the-world pauses with per-interpreter pauses.

Starting in the "suspended" state blocks any _PyThreadState_Attach()
call until the stop-the-world event completes.

_PyThreadState_Suspend now switches to "detached" if there is no active
stop-the-world request.

aisk pushed a commit to aisk/cpython that referenced this pull request

Feb 11, 2024

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

This adds the following functions to implement global and per-interpreter pauses:

* `_PyEval_StopTheWorldAll()` and `_PyEval_StartTheWorldAll()` (for the global runtime)
* `_PyEval_StopTheWorld()` and `_PyEval_StartTheWorld()` (per-interpreter)

(The function names may change.)

These functions are no-ops outside of the `--disable-gil` build.

Glyphack pushed a commit to Glyphack/cpython that referenced this pull request

Sep 2, 2024

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

This adds the following functions to implement global and per-interpreter pauses:

* `_PyEval_StopTheWorldAll()` and `_PyEval_StartTheWorldAll()` (for the global runtime)
* `_PyEval_StopTheWorld()` and `_PyEval_StartTheWorld()` (per-interpreter)

(The function names may change.)

These functions are no-ops outside of the `--disable-gil` build.