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https://github.com/openvswitch/ovs
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15ba057e05
Compiler implementations may provide sub-optimal support for a memory_order passed in as a run-time value (ref. https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html). Document that OVS atomics require the memory order to be passed in as a compile-time constant. It should be noted, however, that when inlining is disabled (i.e., compiling without optimization) even compile-time constants may be passed as run-time values to (non-inlined) functions. Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com> Acked-by: Ben Pfaff <blp@nicira.com>
194 lines
7.0 KiB
C
194 lines
7.0 KiB
C
/*
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* Copyright (c) 2013, 2014 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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/* This header implements atomic operation primitives on GCC 4.x. */
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#ifndef IN_OVS_ATOMIC_H
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#error "This header should only be included indirectly via ovs-atomic.h."
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#endif
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#include "ovs-atomic-locked.h"
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#define OVS_ATOMIC_GCC4P_IMPL 1
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#define ATOMIC(TYPE) TYPE
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#define ATOMIC_BOOL_LOCK_FREE 2
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#define ATOMIC_CHAR_LOCK_FREE 2
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#define ATOMIC_SHORT_LOCK_FREE 2
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#define ATOMIC_INT_LOCK_FREE 2
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#define ATOMIC_LONG_LOCK_FREE (ULONG_MAX <= UINTPTR_MAX ? 2 : 0)
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#define ATOMIC_LLONG_LOCK_FREE (ULLONG_MAX <= UINTPTR_MAX ? 2 : 0)
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#define ATOMIC_POINTER_LOCK_FREE 2
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typedef enum {
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memory_order_relaxed,
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memory_order_consume,
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memory_order_acquire,
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memory_order_release,
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memory_order_acq_rel,
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memory_order_seq_cst
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} memory_order;
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#define IS_LOCKLESS_ATOMIC(OBJECT) (sizeof(OBJECT) <= sizeof(void *))
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#define ATOMIC_VAR_INIT(VALUE) VALUE
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#define atomic_init(OBJECT, VALUE) (*(OBJECT) = (VALUE), (void) 0)
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static inline void
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atomic_thread_fence(memory_order order)
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{
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if (order != memory_order_relaxed) {
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__sync_synchronize();
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}
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}
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static inline void
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atomic_thread_fence_if_seq_cst(memory_order order)
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{
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if (order == memory_order_seq_cst) {
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__sync_synchronize();
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}
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}
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static inline void
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atomic_signal_fence(memory_order order)
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{
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if (order != memory_order_relaxed) {
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asm volatile("" : : : "memory");
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}
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}
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#define atomic_is_lock_free(OBJ) \
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((void) *(OBJ), \
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IS_LOCKLESS_ATOMIC(*(OBJ)) ? 2 : 0)
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#define atomic_store(DST, SRC) \
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atomic_store_explicit(DST, SRC, memory_order_seq_cst)
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#define atomic_store_explicit(DST, SRC, ORDER) \
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({ \
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typeof(DST) dst__ = (DST); \
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typeof(SRC) src__ = (SRC); \
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\
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if (IS_LOCKLESS_ATOMIC(*dst__)) { \
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atomic_thread_fence(ORDER); \
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*dst__ = src__; \
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atomic_thread_fence_if_seq_cst(ORDER); \
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} else { \
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atomic_store_locked(dst__, src__); \
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} \
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(void) 0; \
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})
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#define atomic_read(SRC, DST) \
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atomic_read_explicit(SRC, DST, memory_order_seq_cst)
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#define atomic_read_explicit(SRC, DST, ORDER) \
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({ \
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typeof(DST) dst__ = (DST); \
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typeof(SRC) src__ = (SRC); \
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\
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if (IS_LOCKLESS_ATOMIC(*src__)) { \
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atomic_thread_fence_if_seq_cst(ORDER); \
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*dst__ = *src__; \
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} else { \
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atomic_read_locked(src__, dst__); \
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} \
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(void) 0; \
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})
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#define atomic_compare_exchange_strong(DST, EXP, SRC) \
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({ \
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typeof(DST) dst__ = (DST); \
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typeof(EXP) expp__ = (EXP); \
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typeof(SRC) src__ = (SRC); \
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typeof(SRC) exp__ = *expp__; \
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typeof(SRC) ret__; \
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\
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ret__ = __sync_val_compare_and_swap(dst__, exp__, src__); \
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if (ret__ != exp__) { \
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*expp__ = ret__; \
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} \
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ret__ == exp__; \
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})
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#define atomic_compare_exchange_strong_explicit(DST, EXP, SRC, ORD1, ORD2) \
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((void) (ORD1), (void) (ORD2), \
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atomic_compare_exchange_strong(DST, EXP, SRC))
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#define atomic_compare_exchange_weak \
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atomic_compare_exchange_strong
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#define atomic_compare_exchange_weak_explicit \
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atomic_compare_exchange_strong_explicit
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#define atomic_op__(RMW, OP, ARG, ORIG) \
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({ \
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typeof(RMW) rmw__ = (RMW); \
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typeof(ARG) arg__ = (ARG); \
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typeof(ORIG) orig__ = (ORIG); \
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\
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if (IS_LOCKLESS_ATOMIC(*rmw__)) { \
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*orig__ = __sync_fetch_and_##OP(rmw__, arg__); \
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} else { \
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atomic_op_locked(rmw__, OP, arg__, orig__); \
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} \
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})
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#define atomic_add(RMW, ARG, ORIG) atomic_op__(RMW, add, ARG, ORIG)
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#define atomic_sub(RMW, ARG, ORIG) atomic_op__(RMW, sub, ARG, ORIG)
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#define atomic_or( RMW, ARG, ORIG) atomic_op__(RMW, or, ARG, ORIG)
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#define atomic_xor(RMW, ARG, ORIG) atomic_op__(RMW, xor, ARG, ORIG)
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#define atomic_and(RMW, ARG, ORIG) atomic_op__(RMW, and, ARG, ORIG)
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#define atomic_add_explicit(RMW, OPERAND, ORIG, ORDER) \
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((void) (ORDER), atomic_add(RMW, OPERAND, ORIG))
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#define atomic_sub_explicit(RMW, OPERAND, ORIG, ORDER) \
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((void) (ORDER), atomic_sub(RMW, OPERAND, ORIG))
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#define atomic_or_explicit(RMW, OPERAND, ORIG, ORDER) \
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((void) (ORDER), atomic_or(RMW, OPERAND, ORIG))
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#define atomic_xor_explicit(RMW, OPERAND, ORIG, ORDER) \
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((void) (ORDER), atomic_xor(RMW, OPERAND, ORIG))
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#define atomic_and_explicit(RMW, OPERAND, ORIG, ORDER) \
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((void) (ORDER), atomic_and(RMW, OPERAND, ORIG))
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/* atomic_flag */
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typedef struct {
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int b;
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} atomic_flag;
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#define ATOMIC_FLAG_INIT { false }
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static inline bool
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atomic_flag_test_and_set(volatile atomic_flag *object)
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{
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return __sync_lock_test_and_set(&object->b, 1);
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}
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static inline bool
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atomic_flag_test_and_set_explicit(volatile atomic_flag *object,
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memory_order order OVS_UNUSED)
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{
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return atomic_flag_test_and_set(object);
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}
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static inline void
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atomic_flag_clear(volatile atomic_flag *object)
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{
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__sync_lock_release(&object->b);
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}
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static inline void
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atomic_flag_clear_explicit(volatile atomic_flag *object,
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memory_order order OVS_UNUSED)
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{
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atomic_flag_clear(object);
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}
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