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Title: gh-114271: Fix race in `Thread.join()` by mpage · Pull Request #114839 · python/cpython · GitHub

Open Graph Title: gh-114271: Fix race in `Thread.join()` by mpage · Pull Request #114839 · python/cpython

X Title: gh-114271: Fix race in `Thread.join()` by mpage · Pull Request #114839 · python/cpython

Description: This PR makes thread joining thread-safe in free-threaded builds and fixes gh-116372, which affects both default and free-threaded builds. The combination of _tstate_lock and _ThreadHandle is replaced by _ThreadHandle and the supporting infrastructure for _tstate_lock is removed. Joining a thread now joins its _ThreadHandle. The _ThreadHandles for all threads that we want to join on shutdown (non-daemon threads that were created by the threading module) are tracked in a linked-list attached to the _thread module. At shutdown we iterate over this list and join the handles. There is one wrinkle with this approach: the _MainThread instance. The _MainThread instance is joinable. Previously, it represented whatever thread imported the threading module. Typically this is the main thread of the main interpreter, but in some rare circumstances (embedding scenarios?) it might not be. The previous approach allowed the MainThread instance to be joined even if it wasn't the main thread of the main interpreter, but this isn't possible with the current approach. To work around this we change the _MainThread to always represent the main thread of the runtime, also fixing gh-83223. Issue: gh-114271

Open Graph Description: This PR makes thread joining thread-safe in free-threaded builds and fixes gh-116372, which affects both default and free-threaded builds. The combination of _tstate_lock and _ThreadHandle is repla...

X Description: This PR makes thread joining thread-safe in free-threaded builds and fixes gh-116372, which affects both default and free-threaded builds. The combination of _tstate_lock and _ThreadHandle is repla...

Opengraph URL: https://github.com/python/cpython/pull/114839

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Show all changes 34 commits https://github.com/python/cpython/pull/114839/files
fb13cf6 Fix race in `Thread.join()` mpage Jan 26, 2024 https://github.com/python/cpython/pull/114839/commits/fb13cf6dfa4b5f0420f283823581bcc6e2c9839d
b093e5d 📜🤖 Added by blurb_it. blurb-it[bot] Feb 1, 2024 https://github.com/python/cpython/pull/114839/commits/b093e5db2c9e4abf8f550f1d7b2af636d8f87baf
1039208 Fix NEWS entry mpage Feb 1, 2024 https://github.com/python/cpython/pull/114839/commits/1039208652c0254bccd70e26bd43327e3508ff5e
196081d Work around c-analyzer limitation mpage Feb 5, 2024 https://github.com/python/cpython/pull/114839/commits/196081d6346b994780667812aebea898c142c86d
19d7af1 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Feb 5, 2024 https://github.com/python/cpython/pull/114839/commits/19d7af12f14e615c4cb3f107c49084c8bbfcb314
c86d349 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Feb 7, 2024 https://github.com/python/cpython/pull/114839/commits/c86d349b4e935f3848f7d4dc42912effbdd9c963
40e4b36 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Feb 14, 2024 https://github.com/python/cpython/pull/114839/commits/40e4b36f5d93a4c277679bcc30604fc07d29948d
4ed1083 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Feb 14, 2024 https://github.com/python/cpython/pull/114839/commits/4ed10832b090a902a953e91ad78a6917fd9c7d7d
34b6065 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Mar 1, 2024 https://github.com/python/cpython/pull/114839/commits/34b60651ef36ca65b8957751c7ed85c3af064f37
1c82786 Fix two compilation errors post merge mpage Mar 1, 2024 https://github.com/python/cpython/pull/114839/commits/1c82786c20e2b4e9ba7c2f25bfb3f7d2d5954dbc
0e86cf9 Use ThreadHandle as the single abstraction for thread joining mpage Mar 2, 2024 https://github.com/python/cpython/pull/114839/commits/0e86cf97670d54391cf9f3a2fa444009e8b0a97c
76bde03 Isolate all logic in _threadmodule mpage Mar 4, 2024 https://github.com/python/cpython/pull/114839/commits/76bde036984431df51f2c432b4cd078e6a9ccc58
02123b8 Fix flag mpage Mar 5, 2024 https://github.com/python/cpython/pull/114839/commits/02123b84818079be7cb870fd2f14bd69fbcccee7
24c1d47 Note that the once flag serializes both join and set_done mpage Mar 6, 2024 https://github.com/python/cpython/pull/114839/commits/24c1d476f19260914ace0cbb3449bed6015da9c7
1a1bfde Fix unused variable warning mpage Mar 6, 2024 https://github.com/python/cpython/pull/114839/commits/1a1bfde979cba5059b134ffa278428252952d926
b3c2c45 Rename ThreadHandleObject to PyThreadHandleObject mpage Mar 6, 2024 https://github.com/python/cpython/pull/114839/commits/b3c2c4513b25435b8ad097029ed4dd901dfe024a
7b9d007 Be consistent with documentation of true values mpage Mar 6, 2024 https://github.com/python/cpython/pull/114839/commits/7b9d0074b6581ac9fffd908caa669d9987abc069
5d0dc7a Threads started using `start_joinable_thread` should be daemon thread… mpage Mar 6, 2024 https://github.com/python/cpython/pull/114839/commits/5d0dc7a77d53cf184d8311347203722e2082c72a
11bb826 Remove any remaining handles once the module is cleared mpage Mar 7, 2024 https://github.com/python/cpython/pull/114839/commits/11bb8267daaf987c923bab2197c5fc60bc7ec034
06f6787 Always have a _ThreadHandle in Thread mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/06f67879992e7aeb315834b0656f8a64ef45f227
d56f892 Check main thread handle during shutdown mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/d56f89226bf3e68a60f7ec5b06d442ac5c05f0f9
57e106d Merge branch 'main' into gh-114271-remove-tstate_lock mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/57e106dee41ce32e914afa970796428f99a30c0b
2218c0a Remove vestigial _PyEventRc declarations mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/2218c0a4b6406c303b9e6dcc1383685d3403fdf6
f9d3290 Remove duplicate declaration mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/f9d329078e8423e731c3406ed4e585b4023c790d
a7095e4 Revert order change in `_DummyThread.is_alive` mpage Mar 8, 2024 https://github.com/python/cpython/pull/114839/commits/a7095e47b60465c9a96fd1b2e7c822d7ae040f40
ccd1c2e Merge branch 'main' into gh-114271-remove-tstate_lock mpage Mar 11, 2024 https://github.com/python/cpython/pull/114839/commits/ccd1c2e3bc0db374b7b27c67e91b8109b53b040a
180300c Add handles to shutdown list before starting the thread mpage Mar 11, 2024 https://github.com/python/cpython/pull/114839/commits/180300c70fe8058c0aefa3ed97495ccfcc26008f
c486503 Move some code around to remove need for forward decls mpage Mar 12, 2024 https://github.com/python/cpython/pull/114839/commits/c486503616cb91932b247e6d35b57dc0ac8a8844
3121623 Simplify start failure path mpage Mar 12, 2024 https://github.com/python/cpython/pull/114839/commits/31216236c8bbe1a73b1b7f781a116cabbd49ee45
ee96259 Merge branch 'main' into gh-114271-remove-tstate_lock mpage Mar 15, 2024 https://github.com/python/cpython/pull/114839/commits/ee962590ded8a24a8d8b4c9c00d65afb443fc6b9
dc57ed2 Use infinitive in docstring for _shutdown mpage Mar 15, 2024 https://github.com/python/cpython/pull/114839/commits/dc57ed256a4a72b7c4f4fa91a35240472e631b65
48b86ae Update comment for _make_thread_handle mpage Mar 15, 2024 https://github.com/python/cpython/pull/114839/commits/48b86aee1e3fc74dbe87f8d7d08f61b51c321aec
9a8ea9b Merge branch 'main' into gh-114271-remove-tstate_lock pitrou Mar 16, 2024 https://github.com/python/cpython/pull/114839/commits/9a8ea9b5cca7fdc0e9cf0d3d4b40a87053c8be28
339b2e6 Merge branch 'main' into gh-114271-remove-tstate_lock pitrou Mar 16, 2024 https://github.com/python/cpython/pull/114839/commits/339b2e67784d0bbb157fb39f76e2b3160fbb6911
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