gh-111924: Fix data races when swapping allocators #130287
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CPython current temporarily changes `PYMEM_DOMAIN_RAW` to the default allocator during initialization and shutdown. The motivation is to ensure that core runtime structures are allocated and freed using the same allocator. However, modifying the current allocator changes global state and is not thread-safe even with the GIL. Other threads may be allocating or freeing objects use PYMEM_DOMAIN_RAW; they are not required to hold the GIL to call PyMem_RawMalloc/PyMem_RawFree. This adds new internal-only functions like `_PyMem_DefaultRawMalloc` that aren't affected by calls to `PyMem_SetAllocator()`, so they're appropriate for Python runtime initialization and finalization. Use these calls in places where we previously swapped to the default raw allocator.
kumaraditya303
approved these changes
Feb 20, 2025
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CPython current temporarily changes
PYMEM_DOMAIN_RAWto the default allocator during initialization and shutdown. The motivation is to ensure that core runtime structures are allocated and freed using the same allocator. However, modifying the current allocator changes global state and is not thread-safe even with the GIL. Other threads may be allocating or freeing objects use PYMEM_DOMAIN_RAW; they are not required to hold the GIL to call PyMem_RawMalloc/PyMem_RawFree.This adds new internal-only functions like
_PyMem_DefaultRawMallocthat aren't affected by calls toPyMem_SetAllocator(), so they're appropriate for Python runtime initialization and finalization. Use these calls in places where we previously swapped to the default raw allocator.