570 lines
16 KiB
C
570 lines
16 KiB
C
// This header provides cross-platform low-level atomic operations
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// similar to C11 atomics.
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//
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// Operations are sequentially consistent unless they have a suffix indicating
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// otherwise. If in doubt, prefer the sequentially consistent operations.
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//
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// The "_relaxed" suffix for load and store operations indicates the "relaxed"
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// memory order. They don't provide synchronization, but (roughly speaking)
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// guarantee somewhat sane behavior for races instead of undefined behavior.
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// In practice, they correspond to "normal" hardware load and store
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// instructions, so they are almost as inexpensive as plain loads and stores
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// in C.
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//
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// Note that atomic read-modify-write operations like _Py_atomic_add_* return
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// the previous value of the atomic variable, not the new value.
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//
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// See https://en.cppreference.com/w/c/atomic for more information on C11
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// atomics.
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// See https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2020/p2055r0.pdf
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// "A Relaxed Guide to memory_order_relaxed" for discussion of and common usage
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// or relaxed atomics.
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//
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// Functions with pseudo Python code:
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//
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// def _Py_atomic_load(obj):
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// return obj # sequential consistency
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//
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// def _Py_atomic_load_relaxed(obj):
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// return obj # relaxed consistency
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//
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// def _Py_atomic_store(obj, value):
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// obj = value # sequential consistency
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//
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// def _Py_atomic_store_relaxed(obj, value):
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// obj = value # relaxed consistency
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//
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// def _Py_atomic_exchange(obj, value):
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// # sequential consistency
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// old_obj = obj
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// obj = value
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// return old_obj
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//
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// def _Py_atomic_compare_exchange(obj, expected, desired):
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// # sequential consistency
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// if obj == expected:
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// obj = desired
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// return True
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// else:
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// expected = obj
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// return False
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//
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// def _Py_atomic_add(obj, value):
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// # sequential consistency
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// old_obj = obj
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// obj += value
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// return old_obj
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//
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// def _Py_atomic_and(obj, value):
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// # sequential consistency
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// old_obj = obj
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// obj &= value
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// return old_obj
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//
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// def _Py_atomic_or(obj, value):
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// # sequential consistency
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// old_obj = obj
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// obj |= value
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// return old_obj
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//
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// Other functions:
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//
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// def _Py_atomic_load_ptr_acquire(obj):
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// return obj # acquire
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//
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// def _Py_atomic_store_ptr_release(obj):
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// return obj # release
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//
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// def _Py_atomic_fence_seq_cst():
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// # sequential consistency
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// ...
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//
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// def _Py_atomic_fence_release():
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// # release
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// ...
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#ifndef Py_CPYTHON_ATOMIC_H
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# error "this header file must not be included directly"
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#endif
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// --- _Py_atomic_add --------------------------------------------------------
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// Atomically adds `value` to `obj` and returns the previous value
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static inline int
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_Py_atomic_add_int(int *obj, int value);
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static inline int8_t
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_Py_atomic_add_int8(int8_t *obj, int8_t value);
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static inline int16_t
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_Py_atomic_add_int16(int16_t *obj, int16_t value);
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static inline int32_t
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_Py_atomic_add_int32(int32_t *obj, int32_t value);
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static inline int64_t
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_Py_atomic_add_int64(int64_t *obj, int64_t value);
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static inline intptr_t
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_Py_atomic_add_intptr(intptr_t *obj, intptr_t value);
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static inline unsigned int
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_Py_atomic_add_uint(unsigned int *obj, unsigned int value);
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static inline uint8_t
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_Py_atomic_add_uint8(uint8_t *obj, uint8_t value);
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static inline uint16_t
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_Py_atomic_add_uint16(uint16_t *obj, uint16_t value);
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static inline uint32_t
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_Py_atomic_add_uint32(uint32_t *obj, uint32_t value);
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static inline uint64_t
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_Py_atomic_add_uint64(uint64_t *obj, uint64_t value);
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static inline uintptr_t
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_Py_atomic_add_uintptr(uintptr_t *obj, uintptr_t value);
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static inline Py_ssize_t
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_Py_atomic_add_ssize(Py_ssize_t *obj, Py_ssize_t value);
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// --- _Py_atomic_compare_exchange -------------------------------------------
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// Performs an atomic compare-and-exchange.
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//
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// - If `*obj` and `*expected` are equal, store `desired` into `*obj`
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// and return 1 (success).
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// - Otherwise, store the `*obj` current value into `*expected`
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// and return 0 (failure).
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//
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// These correspond to the C11 atomic_compare_exchange_strong() function.
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static inline int
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_Py_atomic_compare_exchange_int(int *obj, int *expected, int desired);
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static inline int
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_Py_atomic_compare_exchange_int8(int8_t *obj, int8_t *expected, int8_t desired);
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static inline int
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_Py_atomic_compare_exchange_int16(int16_t *obj, int16_t *expected, int16_t desired);
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static inline int
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_Py_atomic_compare_exchange_int32(int32_t *obj, int32_t *expected, int32_t desired);
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static inline int
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_Py_atomic_compare_exchange_int64(int64_t *obj, int64_t *expected, int64_t desired);
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static inline int
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_Py_atomic_compare_exchange_intptr(intptr_t *obj, intptr_t *expected, intptr_t desired);
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static inline int
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_Py_atomic_compare_exchange_uint(unsigned int *obj, unsigned int *expected, unsigned int desired);
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static inline int
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_Py_atomic_compare_exchange_uint8(uint8_t *obj, uint8_t *expected, uint8_t desired);
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static inline int
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_Py_atomic_compare_exchange_uint16(uint16_t *obj, uint16_t *expected, uint16_t desired);
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static inline int
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_Py_atomic_compare_exchange_uint32(uint32_t *obj, uint32_t *expected, uint32_t desired);
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static inline int
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_Py_atomic_compare_exchange_uint64(uint64_t *obj, uint64_t *expected, uint64_t desired);
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static inline int
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_Py_atomic_compare_exchange_uintptr(uintptr_t *obj, uintptr_t *expected, uintptr_t desired);
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static inline int
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_Py_atomic_compare_exchange_ssize(Py_ssize_t *obj, Py_ssize_t *expected, Py_ssize_t desired);
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// NOTE: `obj` and `expected` are logically `void**` types, but we use `void*`
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// so that we can pass types like `PyObject**` without a cast.
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static inline int
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_Py_atomic_compare_exchange_ptr(void *obj, void *expected, void *value);
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// --- _Py_atomic_exchange ---------------------------------------------------
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// Atomically replaces `*obj` with `value` and returns the previous value of `*obj`.
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static inline int
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_Py_atomic_exchange_int(int *obj, int value);
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static inline int8_t
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_Py_atomic_exchange_int8(int8_t *obj, int8_t value);
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static inline int16_t
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_Py_atomic_exchange_int16(int16_t *obj, int16_t value);
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static inline int32_t
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_Py_atomic_exchange_int32(int32_t *obj, int32_t value);
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static inline int64_t
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_Py_atomic_exchange_int64(int64_t *obj, int64_t value);
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static inline intptr_t
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_Py_atomic_exchange_intptr(intptr_t *obj, intptr_t value);
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static inline unsigned int
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_Py_atomic_exchange_uint(unsigned int *obj, unsigned int value);
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static inline uint8_t
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_Py_atomic_exchange_uint8(uint8_t *obj, uint8_t value);
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static inline uint16_t
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_Py_atomic_exchange_uint16(uint16_t *obj, uint16_t value);
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static inline uint32_t
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_Py_atomic_exchange_uint32(uint32_t *obj, uint32_t value);
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static inline uint64_t
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_Py_atomic_exchange_uint64(uint64_t *obj, uint64_t value);
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static inline uintptr_t
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_Py_atomic_exchange_uintptr(uintptr_t *obj, uintptr_t value);
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static inline Py_ssize_t
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_Py_atomic_exchange_ssize(Py_ssize_t *obj, Py_ssize_t value);
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static inline void *
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_Py_atomic_exchange_ptr(void *obj, void *value);
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// --- _Py_atomic_and --------------------------------------------------------
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// Performs `*obj &= value` atomically and returns the previous value of `*obj`.
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static inline uint8_t
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_Py_atomic_and_uint8(uint8_t *obj, uint8_t value);
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static inline uint16_t
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_Py_atomic_and_uint16(uint16_t *obj, uint16_t value);
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static inline uint32_t
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_Py_atomic_and_uint32(uint32_t *obj, uint32_t value);
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static inline uint64_t
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_Py_atomic_and_uint64(uint64_t *obj, uint64_t value);
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static inline uintptr_t
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_Py_atomic_and_uintptr(uintptr_t *obj, uintptr_t value);
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// --- _Py_atomic_or ---------------------------------------------------------
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// Performs `*obj |= value` atomically and returns the previous value of `*obj`.
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static inline uint8_t
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_Py_atomic_or_uint8(uint8_t *obj, uint8_t value);
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static inline uint16_t
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_Py_atomic_or_uint16(uint16_t *obj, uint16_t value);
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static inline uint32_t
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_Py_atomic_or_uint32(uint32_t *obj, uint32_t value);
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static inline uint64_t
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_Py_atomic_or_uint64(uint64_t *obj, uint64_t value);
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static inline uintptr_t
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_Py_atomic_or_uintptr(uintptr_t *obj, uintptr_t value);
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// --- _Py_atomic_load -------------------------------------------------------
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// Atomically loads `*obj` (sequential consistency)
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static inline int
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_Py_atomic_load_int(const int *obj);
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static inline int8_t
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_Py_atomic_load_int8(const int8_t *obj);
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static inline int16_t
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_Py_atomic_load_int16(const int16_t *obj);
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static inline int32_t
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_Py_atomic_load_int32(const int32_t *obj);
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static inline int64_t
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_Py_atomic_load_int64(const int64_t *obj);
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static inline intptr_t
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_Py_atomic_load_intptr(const intptr_t *obj);
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static inline uint8_t
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_Py_atomic_load_uint8(const uint8_t *obj);
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static inline uint16_t
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_Py_atomic_load_uint16(const uint16_t *obj);
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static inline uint32_t
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_Py_atomic_load_uint32(const uint32_t *obj);
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static inline uint64_t
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_Py_atomic_load_uint64(const uint64_t *obj);
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static inline uintptr_t
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_Py_atomic_load_uintptr(const uintptr_t *obj);
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static inline unsigned int
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_Py_atomic_load_uint(const unsigned int *obj);
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static inline Py_ssize_t
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_Py_atomic_load_ssize(const Py_ssize_t *obj);
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static inline void *
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_Py_atomic_load_ptr(const void *obj);
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// --- _Py_atomic_load_relaxed -----------------------------------------------
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// Loads `*obj` (relaxed consistency, i.e., no ordering)
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static inline int
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_Py_atomic_load_int_relaxed(const int *obj);
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static inline int8_t
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_Py_atomic_load_int8_relaxed(const int8_t *obj);
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static inline int16_t
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_Py_atomic_load_int16_relaxed(const int16_t *obj);
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static inline int32_t
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_Py_atomic_load_int32_relaxed(const int32_t *obj);
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static inline int64_t
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_Py_atomic_load_int64_relaxed(const int64_t *obj);
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static inline intptr_t
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_Py_atomic_load_intptr_relaxed(const intptr_t *obj);
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static inline uint8_t
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_Py_atomic_load_uint8_relaxed(const uint8_t *obj);
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static inline uint16_t
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_Py_atomic_load_uint16_relaxed(const uint16_t *obj);
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static inline uint32_t
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_Py_atomic_load_uint32_relaxed(const uint32_t *obj);
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static inline uint64_t
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_Py_atomic_load_uint64_relaxed(const uint64_t *obj);
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static inline uintptr_t
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_Py_atomic_load_uintptr_relaxed(const uintptr_t *obj);
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static inline unsigned int
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_Py_atomic_load_uint_relaxed(const unsigned int *obj);
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static inline Py_ssize_t
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_Py_atomic_load_ssize_relaxed(const Py_ssize_t *obj);
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static inline void *
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_Py_atomic_load_ptr_relaxed(const void *obj);
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static inline unsigned long long
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_Py_atomic_load_ullong_relaxed(const unsigned long long *obj);
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// --- _Py_atomic_store ------------------------------------------------------
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// Atomically performs `*obj = value` (sequential consistency)
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static inline void
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_Py_atomic_store_int(int *obj, int value);
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static inline void
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_Py_atomic_store_int8(int8_t *obj, int8_t value);
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static inline void
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_Py_atomic_store_int16(int16_t *obj, int16_t value);
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static inline void
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_Py_atomic_store_int32(int32_t *obj, int32_t value);
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static inline void
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_Py_atomic_store_int64(int64_t *obj, int64_t value);
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static inline void
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_Py_atomic_store_intptr(intptr_t *obj, intptr_t value);
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static inline void
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_Py_atomic_store_uint8(uint8_t *obj, uint8_t value);
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static inline void
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_Py_atomic_store_uint16(uint16_t *obj, uint16_t value);
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static inline void
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_Py_atomic_store_uint32(uint32_t *obj, uint32_t value);
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static inline void
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_Py_atomic_store_uint64(uint64_t *obj, uint64_t value);
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static inline void
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_Py_atomic_store_uintptr(uintptr_t *obj, uintptr_t value);
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static inline void
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_Py_atomic_store_uint(unsigned int *obj, unsigned int value);
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static inline void
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_Py_atomic_store_ptr(void *obj, void *value);
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static inline void
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_Py_atomic_store_ssize(Py_ssize_t* obj, Py_ssize_t value);
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// --- _Py_atomic_store_relaxed ----------------------------------------------
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// Stores `*obj = value` (relaxed consistency, i.e., no ordering)
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static inline void
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_Py_atomic_store_int_relaxed(int *obj, int value);
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static inline void
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_Py_atomic_store_int8_relaxed(int8_t *obj, int8_t value);
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static inline void
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_Py_atomic_store_int16_relaxed(int16_t *obj, int16_t value);
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static inline void
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_Py_atomic_store_int32_relaxed(int32_t *obj, int32_t value);
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static inline void
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_Py_atomic_store_int64_relaxed(int64_t *obj, int64_t value);
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static inline void
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_Py_atomic_store_intptr_relaxed(intptr_t *obj, intptr_t value);
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static inline void
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_Py_atomic_store_uint8_relaxed(uint8_t* obj, uint8_t value);
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static inline void
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_Py_atomic_store_uint16_relaxed(uint16_t *obj, uint16_t value);
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static inline void
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_Py_atomic_store_uint32_relaxed(uint32_t *obj, uint32_t value);
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static inline void
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_Py_atomic_store_uint64_relaxed(uint64_t *obj, uint64_t value);
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static inline void
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_Py_atomic_store_uintptr_relaxed(uintptr_t *obj, uintptr_t value);
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static inline void
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_Py_atomic_store_uint_relaxed(unsigned int *obj, unsigned int value);
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static inline void
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_Py_atomic_store_ptr_relaxed(void *obj, void *value);
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static inline void
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_Py_atomic_store_ssize_relaxed(Py_ssize_t *obj, Py_ssize_t value);
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static inline void
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_Py_atomic_store_ullong_relaxed(unsigned long long *obj,
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unsigned long long value);
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// --- _Py_atomic_load_ptr_acquire / _Py_atomic_store_ptr_release ------------
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// Loads `*obj` (acquire operation)
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static inline void *
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_Py_atomic_load_ptr_acquire(const void *obj);
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static inline uintptr_t
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_Py_atomic_load_uintptr_acquire(const uintptr_t *obj);
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// Stores `*obj = value` (release operation)
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static inline void
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_Py_atomic_store_ptr_release(void *obj, void *value);
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static inline void
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_Py_atomic_store_uintptr_release(uintptr_t *obj, uintptr_t value);
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static inline void
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_Py_atomic_store_ssize_release(Py_ssize_t *obj, Py_ssize_t value);
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static inline void
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_Py_atomic_store_int_release(int *obj, int value);
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static inline int
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_Py_atomic_load_int_acquire(const int *obj);
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static inline void
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_Py_atomic_store_uint32_release(uint32_t *obj, uint32_t value);
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static inline void
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_Py_atomic_store_uint64_release(uint64_t *obj, uint64_t value);
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static inline uint64_t
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_Py_atomic_load_uint64_acquire(const uint64_t *obj);
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static inline uint32_t
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_Py_atomic_load_uint32_acquire(const uint32_t *obj);
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static inline Py_ssize_t
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_Py_atomic_load_ssize_acquire(const Py_ssize_t *obj);
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// --- _Py_atomic_fence ------------------------------------------------------
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// Sequential consistency fence. C11 fences have complex semantics. When
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// possible, use the atomic operations on variables defined above, which
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// generally do not require explicit use of a fence.
|
|
// See https://en.cppreference.com/w/cpp/atomic/atomic_thread_fence
|
|
static inline void _Py_atomic_fence_seq_cst(void);
|
|
|
|
// Acquire fence
|
|
static inline void _Py_atomic_fence_acquire(void);
|
|
|
|
// Release fence
|
|
static inline void _Py_atomic_fence_release(void);
|
|
|
|
|
|
#ifndef _Py_USE_GCC_BUILTIN_ATOMICS
|
|
# if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8))
|
|
# define _Py_USE_GCC_BUILTIN_ATOMICS 1
|
|
# elif defined(__clang__)
|
|
# if __has_builtin(__atomic_load)
|
|
# define _Py_USE_GCC_BUILTIN_ATOMICS 1
|
|
# endif
|
|
# endif
|
|
#endif
|
|
|
|
#if _Py_USE_GCC_BUILTIN_ATOMICS
|
|
# define Py_ATOMIC_GCC_H
|
|
# include "pyatomic_gcc.h"
|
|
# undef Py_ATOMIC_GCC_H
|
|
#elif __STDC_VERSION__ >= 201112L && !defined(__STDC_NO_ATOMICS__)
|
|
# define Py_ATOMIC_STD_H
|
|
# include "pyatomic_std.h"
|
|
# undef Py_ATOMIC_STD_H
|
|
#elif defined(_MSC_VER)
|
|
# define Py_ATOMIC_MSC_H
|
|
# include "pyatomic_msc.h"
|
|
# undef Py_ATOMIC_MSC_H
|
|
#else
|
|
# error "no available pyatomic implementation for this platform/compiler"
|
|
#endif
|
|
|
|
|
|
// --- aliases ---------------------------------------------------------------
|
|
|
|
#if SIZEOF_LONG == 8
|
|
# define _Py_atomic_load_ulong(p) \
|
|
_Py_atomic_load_uint64((uint64_t *)p)
|
|
# define _Py_atomic_load_ulong_relaxed(p) \
|
|
_Py_atomic_load_uint64_relaxed((uint64_t *)p)
|
|
# define _Py_atomic_store_ulong(p, v) \
|
|
_Py_atomic_store_uint64((uint64_t *)p, v)
|
|
# define _Py_atomic_store_ulong_relaxed(p, v) \
|
|
_Py_atomic_store_uint64_relaxed((uint64_t *)p, v)
|
|
#elif SIZEOF_LONG == 4
|
|
# define _Py_atomic_load_ulong(p) \
|
|
_Py_atomic_load_uint32((uint32_t *)p)
|
|
# define _Py_atomic_load_ulong_relaxed(p) \
|
|
_Py_atomic_load_uint32_relaxed((uint32_t *)p)
|
|
# define _Py_atomic_store_ulong(p, v) \
|
|
_Py_atomic_store_uint32((uint32_t *)p, v)
|
|
# define _Py_atomic_store_ulong_relaxed(p, v) \
|
|
_Py_atomic_store_uint32_relaxed((uint32_t *)p, v)
|
|
#else
|
|
# error "long must be 4 or 8 bytes in size"
|
|
#endif // SIZEOF_LONG
|