[3.13] gh-118727: Don't drop the GIL in drop_gil() unless the current thread holds it (GH-118745) #119474
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…t thread holds it (pythonGH-118745) `drop_gil()` assumes that its caller is attached, which means that the current thread holds the GIL if and only if the GIL is enabled, and the enabled-state of the GIL won't change. This isn't true, though, because `detach_thread()` calls `_PyEval_ReleaseLock()` after detaching and `_PyThreadState_DeleteCurrent()` calls it after removing the current thread from consideration for stop-the-world requests (effectively detaching it). Fix this by remembering whether or not a thread acquired the GIL when it last attached, in `PyThreadState._status.holds_gil`, and check this in `drop_gil()` instead of `gil->enabled`. This fixes a crash in `test_multiprocessing_pool_circular_import()`, so I've reenabled it. (cherry picked from commit be1dfcc) Co-authored-by: Brett Simmers <swtaarrs@users.noreply.github.com>
miss-islington requested review from brettcannon, ericsnowcurrently, ncoghlan and warsaw as code owners 
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drop_gil()assumes that its caller is attached, which means that the currentthread holds the GIL if and only if the GIL is enabled, and the enabled-state
of the GIL won't change. This isn't true, though, because
detach_thread()calls
_PyEval_ReleaseLock()after detaching and_PyThreadState_DeleteCurrent()calls it after removing the current threadfrom consideration for stop-the-world requests (effectively detaching it).
Fix this by remembering whether or not a thread acquired the GIL when it last
attached, in
PyThreadState._status.holds_gil, and check this indrop_gil()instead of
gil->enabled.This fixes a crash in
test_multiprocessing_pool_circular_import(), so I'vereenabled it.
(cherry picked from commit be1dfcc)
Co-authored-by: Brett Simmers swtaarrs@users.noreply.github.com
PyThreadState_DeleteCurrent: drop_gil: GIL is not locked (free-threading) #118727