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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Add HEAD_ISLOCKED to wrap GIL check","articleBody":"# Feature or enhancement\r\n\r\n### Proposal:\r\n\r\nThis issue is extracted from https://github.com/python/cpython/pull/125561.\r\nWhen interpretation_clear is changed, the `PyThreadState_Clear` function needs to be called when `HEAD_LOCK` is not held, but in fact we cannot be sure, but it existed before the change. In fact, PR solves the competition, but does not eliminate the risk of deadlock, so I give the following solution.\r\n\r\nFor `PyThreadState_Clear`, I want to add a `HEAD_ISLOCKED` macro to wrap `PyMutex_IsLocked`. This allows a check to be made when UNLOCK is called. Otherwise, if HEAD_LOCK is not called in the context, an is unlock error will occur when HEAD_UNLOCK is called. But in fact, we cannot be sure whether HEAD_LOCK is called in the context, and HEAD_IS_LOCK can be used to check it.\r\n\r\nchanged\r\n```\r\ndiff --git a/Python/pystate.c b/Python/pystate.c\r\nindex 6b4e1d470f8..dc67e50bc27 100644\r\n--- a/Python/pystate.c\r\n+++ b/Python/pystate.c\r\n@@ -796,6 +796,7 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)\r\n         // See https://github.com/python/cpython/issues/102126\r\n         // Must be called without HEAD_LOCK held as it can deadlock\r\n         // if any finalizer tries to acquire that lock.\r\n+        HEAD_UNLOCK(\u0026_PyRuntime);\r\n         PyThreadState_Clear(p);\r\n         p = p-\u003enext;\r\n     }\r\n```\r\nThe above code will show **no locked** when the context does not hold HEAD_LOCK, but this is not certain. So I want to add an if statement in front to unlock it when holding HEAD_LOCK. Ensure that there is no deadlock when calling `PyThreadState_Clear`.\r\n```\r\nif (HEAD_ISLOCKED(\u0026_PyRuntime)) {\r\n    HEAD_UNLOCK(\u0026_PyRuntime);\r\n}\r\nPyThreadState_Clear(p);\r\n```\r\n### Has this already been discussed elsewhere?\r\n\r\nNo response given\r\n\r\n### Links to previous discussion of this feature:\r\n\r\n_No response_","author":{"url":"https://github.com/rruuaanng","@type":"Person","name":"rruuaanng"},"datePublished":"2024-10-24T01:47:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/125908/cpython/issues/125908"}