gh-116738: Make _codecs module thread-safe
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colesbury
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Apr 10, 2024
colesbury
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Apr 15, 2024
…istry's return type
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This should be ready to go as of my last commit - let me know if any other changes are needed. |
colesbury
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May 2, 2024
SonicField
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May 8, 2024
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.
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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
PyInterpreterStateto a struct declared inpycore_codecs.h.In free-threaded builds, add two mutexes to
codecs_state, one to synchronize operations onsearch_path, and one to synchronize initialization._PyCodecRegistry_Init()is now_PyCodecRegistry_EnsureInit(), and is called unconditionally to ensure initialization, rather than only when initialization is needed. When it returns 0 (as opposed to -1 to indicate an error), thePyObject *members ofcodecs_statecan be read without further synchronization.Operations that mutate
codecs.search_pathmust be performed while holdingcodecs.search_path_mutex. This allowsPyCodec_Unregister()to search for and delete a specific item from the list. Becausesearch_path_mutexis used as a normal mutex and not a critical section, we must be extremely careful with operations called while holding it.Issue: Audit all built-in modules for thread safety #116738