d4ac7582f3
This introduces a backport of C11 atomics. It has four implementations; ranked in order of preference, they are: - GCC/Clang __atomic builtins - GCC/Clang __sync builtins - MSVC _Interlocked builtins - C11 atomics, from <stdatomic.h> The primary advantages are: - Close adherence to the standard API gives us a defined memory model. - Type safety: atomic objects are now separate types from non-atomic ones, so that it's impossible to mix up atomic and non-atomic updates (which is undefined behavior that compilers are starting to take advantage of). - Efficiency: we can specify ordering for operations, avoiding fences and atomic operations on strongly ordered architectures (example: `atomic_write_u32(ptr, val);` involves a CAS loop, whereas `atomic_store(ptr, val, ATOMIC_RELEASE);` is a plain store. This diff leaves in the current atomics API (implementing them in terms of the backport). This lets us transition uses over piecemeal. Testing: This is by nature hard to test. I've manually tested the first three options on Linux on gcc by futzing with the #defines manually, on freebsd with gcc and clang, on MSVC, and on OS X with clang. All of these were x86 machines though, and we don't have any test infrastructure set up for non-x86 platforms.
126 lines
4.0 KiB
C
126 lines
4.0 KiB
C
#ifndef JEMALLOC_INTERNAL_ATOMIC_GCC_ATOMIC_H
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#define JEMALLOC_INTERNAL_ATOMIC_GCC_ATOMIC_H
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#define ATOMIC_INIT(...) {__VA_ARGS__}
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typedef enum {
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atomic_memory_order_relaxed,
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atomic_memory_order_acquire,
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atomic_memory_order_release,
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atomic_memory_order_acq_rel,
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atomic_memory_order_seq_cst
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} atomic_memory_order_t;
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ATOMIC_INLINE int
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atomic_enum_to_builtin(atomic_memory_order_t mo) {
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switch (mo) {
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case atomic_memory_order_relaxed:
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return __ATOMIC_RELAXED;
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case atomic_memory_order_acquire:
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return __ATOMIC_ACQUIRE;
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case atomic_memory_order_release:
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return __ATOMIC_RELEASE;
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case atomic_memory_order_acq_rel:
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return __ATOMIC_ACQ_REL;
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case atomic_memory_order_seq_cst:
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return __ATOMIC_SEQ_CST;
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}
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/* Can't actually happen; the switch is exhaustive. */
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return __ATOMIC_SEQ_CST;
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}
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ATOMIC_INLINE void
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atomic_fence(atomic_memory_order_t mo) {
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__atomic_thread_fence(atomic_enum_to_builtin(mo));
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}
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#define JEMALLOC_GENERATE_ATOMICS(type, short_type, \
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/* unused */ lg_size) \
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typedef struct { \
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type repr; \
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} atomic_##short_type##_t; \
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\
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ATOMIC_INLINE type \
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atomic_load_##short_type(const atomic_##short_type##_t *a, \
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atomic_memory_order_t mo) { \
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type result; \
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__atomic_load(&a->repr, &result, atomic_enum_to_builtin(mo)); \
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return result; \
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} \
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\
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ATOMIC_INLINE void \
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atomic_store_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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__atomic_store(&a->repr, &val, atomic_enum_to_builtin(mo)); \
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} \
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\
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ATOMIC_INLINE type \
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atomic_exchange_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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type result; \
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__atomic_exchange(&a->repr, &val, &result, \
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atomic_enum_to_builtin(mo)); \
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return result; \
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} \
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\
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ATOMIC_INLINE bool \
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atomic_compare_exchange_weak_##short_type(atomic_##short_type##_t *a, \
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type *expected, type desired, atomic_memory_order_t success_mo, \
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atomic_memory_order_t failure_mo) { \
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return __atomic_compare_exchange(&a->repr, expected, &desired, \
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true, atomic_enum_to_builtin(success_mo), \
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atomic_enum_to_builtin(failure_mo)); \
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} \
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\
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ATOMIC_INLINE bool \
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atomic_compare_exchange_strong_##short_type(atomic_##short_type##_t *a, \
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type *expected, type desired, atomic_memory_order_t success_mo, \
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atomic_memory_order_t failure_mo) { \
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return __atomic_compare_exchange(&a->repr, expected, &desired, \
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false, \
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atomic_enum_to_builtin(success_mo), \
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atomic_enum_to_builtin(failure_mo)); \
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}
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#define JEMALLOC_GENERATE_INT_ATOMICS(type, short_type, \
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/* unused */ lg_size) \
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JEMALLOC_GENERATE_ATOMICS(type, short_type, /* unused */ lg_size) \
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\
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ATOMIC_INLINE type \
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atomic_fetch_add_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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return __atomic_fetch_add(&a->repr, val, \
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atomic_enum_to_builtin(mo)); \
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} \
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\
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ATOMIC_INLINE type \
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atomic_fetch_sub_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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return __atomic_fetch_sub(&a->repr, val, \
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atomic_enum_to_builtin(mo)); \
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} \
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\
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ATOMIC_INLINE type \
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atomic_fetch_and_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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return __atomic_fetch_and(&a->repr, val, \
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atomic_enum_to_builtin(mo)); \
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} \
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\
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ATOMIC_INLINE type \
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atomic_fetch_or_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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return __atomic_fetch_or(&a->repr, val, \
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atomic_enum_to_builtin(mo)); \
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} \
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\
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ATOMIC_INLINE type \
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atomic_fetch_xor_##short_type(atomic_##short_type##_t *a, type val, \
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atomic_memory_order_t mo) { \
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return __atomic_fetch_xor(&a->repr, val, \
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atomic_enum_to_builtin(mo)); \
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}
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#endif /* JEMALLOC_INTERNAL_ATOMIC_GCC_ATOMIC_H */
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