assembly - 如何以原子方式读取 x86 ASM 中的值？

Question

我知道如何在 x86 ASM 中以原子方式写入值。但是我怎么读呢？ LOCK 前缀不能与 mov 一起使用。

为了增加值(value)，我正在做:

lock inc dword ptr Counter

如何以线程安全的方式读取 Counter？

Answer 1

正如我在 this 中向您解释的那样邮政:

Accesses to cacheable memory that are split across bus widths, cache lines, and page boundaries are not guaranteed to be atomic by the Intel Core 2 Duo, Intel Core Duo, Pentium M, Pentium 4, Intel Xeon, P6 family, Pentium, and Intel486 processors. The Intel Core 2 Duo, Intel Core Duo, Pentium M, Pentium 4, Intel Xeon, and P6 family processors provide bus control signals that permit external memory subsystems to make split accesses atomic; however, nonaligned data accesses will seriously impact the performance of the processor and should be avoided.

所以使用:

LOCK        CMPXCHG   EAX, [J]

LOCK CMPXCHG 首先隔离缓存，然后将 EAX 与目标值进行比较，如果目标值不相等，则 EAX 中的结果为目标值。

编辑:
链接到:

Intel® 64 and IA-32 Architectures Software Developer’s Manuals

在 Volume 3A: System Programming Guide检查第 8.1.1 节

同时检查: Optimization Reference Manual section: CHAPTER 7 OPTIMIZING CACHE USAGE