mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-10-06 23:21:06 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 10

gh-114271: Make _thread.ThreadHandle thread-safe in free-threaded builds (GH-115190)

Browse source 
Make `_thread.ThreadHandle` thread-safe in free-threaded builds

We protect the mutable state of `ThreadHandle` using a `_PyOnceFlag`.
Concurrent operations (i.e. `join` or `detach`) on `ThreadHandle` block
until it is their turn to execute or an earlier operation succeeds.
Once an operation has been applied successfully all future operations
complete immediately.

The `join()` method is now idempotent. It may be called multiple times
but the underlying OS thread will only be joined once. After `join()`
succeeds, any future calls to `join()` will succeed immediately.

The internal thread handle `detach()` method has been removed.
This commit is contained in:
mpage 2024-03-01 13:43:12 -08:00 • committed by GitHub
parent 5e0c7bc1d3
commit 9e88173d36
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
5 changed files with 230 additions and 106 deletions
Download patch file Download diff file Expand all files Collapse all files

24
Lib/threading.py
View file

@ -931,7 +931,6 @@ class Thread:
if _HAVE_THREAD_NATIVE_ID:
self._native_id = None
self._tstate_lock = None
self._join_lock = None
self._handle = None
self._started = Event()
self._is_stopped = False
@ -956,14 +955,11 @@ class Thread:
if self._tstate_lock is not None:
self._tstate_lock._at_fork_reinit()
self._tstate_lock.acquire()
if self._join_lock is not None:
self._join_lock._at_fork_reinit()
else:
# This thread isn't alive after fork: it doesn't have a tstate
# anymore.
self._is_stopped = True
self._tstate_lock = None
self._join_lock = None
self._handle = None
def __repr__(self):
@ -996,8 +992,6 @@ class Thread:
if self._started.is_set():
raise RuntimeError("threads can only be started once")
self._join_lock = _allocate_lock()
with _active_limbo_lock:
_limbo[self] = self
try:
@ -1167,17 +1161,9 @@ class Thread:
self._join_os_thread()
def _join_os_thread(self):
join_lock = self._join_lock
if join_lock is None:
return
with join_lock:
# Calling join() multiple times would raise an exception
# in one of the callers.
if self._handle is not None:
self._handle.join()
self._handle = None
# No need to keep this around
self._join_lock = None
# self._handle may be cleared post-fork
if self._handle is not None:
self._handle.join()
def _wait_for_tstate_lock(self, block=True, timeout=-1):
# Issue #18808: wait for the thread state to be gone.
@ -1478,6 +1464,10 @@ class _MainThread(Thread):
with _active_limbo_lock:
_active[self._ident] = self
def _join_os_thread(self):
# No ThreadHandle for main thread
pass
# Helper thread-local instance to detect when a _DummyThread
# is collected. Not a part of the public API.