gh-119053: Implement the fast path for list.__getitem__ (gh-119112)
(cherry picked from commit ab4263a82a)
Co-authored-by: Donghee Na <donghee.na@python.org>
The `list_preallocate_exact` function did not zero initialize array
contents. In the free-threaded build, this could expose uninitialized
memory to concurrent readers between the call to
`list_preallocate_exact` and the filling of the array contents with
items.
(cherry picked from commit 2402715e10)
Co-authored-by: Sam Gross <colesbury@gmail.com>
gh-118849: Fix "code will never be executed" warning in `dictobject.c` (GH-118850)
(cherry picked from commit 82abe75e77)
Co-authored-by: Nikita Sobolev <mail@sobolevn.me>
Use relaxed atomics when reading / writing to the field. There are still a
few places in the GC where we do not use atomics. Those should be safe as
the world is stopped.
(cherry picked from commit cb6f75a32c)
Co-authored-by: mpage <mpage@meta.com>
We already intern and immortalize most string constants. In the
free-threaded build, other constants can be a source of reference count
contention because they are shared by all threads running the same code
objects.
Add _PyType_LookupRef and use incref before setting attribute on type
Makes setting an attribute on a class and signaling type modified atomic
Avoid adding re-entrancy exposing the type cache in an inconsistent state by decrefing after type is updated
This interns the strings for `co_filename`, `co_name`, and `co_qualname`
on codeobjects in the free-threaded build. This partially addresses a
reference counting bottleneck when creating closures concurrently. The
closures take the name and qualified name from the code object.
This PR adds the ability to enable the GIL if it was disabled at
interpreter startup, and modifies the multi-phase module initialization
path to enable the GIL when loading a module, unless that module's spec
includes a slot indicating it can run safely without the GIL.
PEP 703 called the constant for the slot `Py_mod_gil_not_used`; I went
with `Py_MOD_GIL_NOT_USED` for consistency with gh-104148.
A warning will be issued up to once per interpreter for the first
GIL-using module that is loaded. If `-v` is given, a shorter message
will be printed to stderr every time a GIL-using module is loaded
(including the first one that issues a warning).
The module itself is a thin wrapper around calls to functions in
`Python/codecs.c`, so that's where the meaningful changes happened:
- Move codecs-related state that lives on `PyInterpreterState` to a
struct declared in `pycore_codecs.h`.
- In free-threaded builds, add a mutex to `codecs_state` to synchronize
operations on `search_path`. Because `search_path_mutex` is used as a
normal mutex and not a critical section, we must be extremely careful
with operations called while holding it.
- The codec registry is explicitly initialized as part of
`_PyUnicode_InitEncodings` to simplify thread-safety.
The code for Tier 2 is now only compiled when configured
with `--enable-experimental-jit[=yes|interpreter]`.
We drop support for `PYTHON_UOPS` and -`Xuops`,
but you can disable the interpreter or JIT
at runtime by setting `PYTHON_JIT=0`.
You can also build it without enabling it by default
using `--enable-experimental-jit=yes-off`;
enable with `PYTHON_JIT=1`.
On Windows, the `build.bat` script supports
`--experimental-jit`, `--experimental-jit-off`,
`--experimental-interpreter`.
In the C code, `_Py_JIT` is defined as before
when the JIT is enabled; the new variable
`_Py_TIER2` is defined when the JIT *or* the
interpreter is enabled. It is actually a bitmask:
1: JIT; 2: default-off; 4: interpreter.
Deferred reference counting is not fully implemented yet. As a temporary
measure, we immortalize objects that would use deferred reference
counting to avoid multi-threaded scaling bottlenecks.
This is only performed in the free-threaded build once the first
non-main thread is started. Additionally, some tests, including refleak
tests, suppress this behavior.
It's not safe to raise an exception in `PyObject_ClearWeakRefs()` if one
is not already set, since it may be called by `_Py_Dealloc()`, which
requires that the active exception does not change.
Additionally, make sure we clear the weakrefs even when tuple allocation
fails.
Miss Islington (bot)
Tian Gao
James Hilton-Balfe
Sam Gross
Dino Viehland
Mark Shannon
Thomas Grainger
Petr Viktorin
mpage
Brett Simmers
Jelle Zijlstra
Pablo Galindo Salgado
Guido van Rossum
Irit Katriel
Donghee Na
neonene
Serhiy Storchaka
Shantanu
Kirill Podoprigora