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ATOMIC_OP_RETURN宏定义了内存屏蔽操作smp_mb,不过"memory"命令也有内存屏蔽的功能;
#define ATOMIC_OP_RETURN(op, asm_op) \
static inline int atomic_##op##_return(int i, atomic_t *v) \
{ \
asm volatile("// atomic_" #op "_return\n" \
... ...
: "memory"); \
\
smp_mb(); \
}
#define ATOMIC_OPS(op, asm_op) \
ATOMIC_OP(op, asm_op) \
ATOMIC_OP_RETURN(op, asm_op)
下面两个宏定义了4个原子操作:
ATOMIC_OPS(add, add) -> atomic_add/atomic_add_return
ATOMIC_OPS(sub, sub) -> atomic_sub/atomic_sub_return
其它操作基本都是基于这两个操作:
#define atomic_inc(v) atomic_add(1, v)
#define atomic_dec(v) atomic_sub(1, v)
#define atomic_inc_and_test(v) (atomic_add_return(1, v) == 0)
#define atomic_dec_and_test(v) (atomic_sub_return(1, v) == 0)
... ...
atomic_read/atomic_set/atomic_add/atomic_sub没发现内存屏蔽,带return的操作有多处理器内存屏蔽; |
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