当多个线程同时*读取*同一内存时，这是数据竞争吗？
Is it a data-race when several thread *read* the same memory at the same time?
cppreference.com says:
Threads and data races
When an evaluation of an expression writes to a memory location and
another evaluation reads or modifies the same memory location, the
expressions are said to conflict. A program that has two conflicting
evaluations has a data race unless...
这里说的是'thread1-write thread2-read'（W-R）的场景和'thread1-write thread2-write'（W-W）的场景。
'thread1-read thread2-read' (R-R) 呢？
没有。只要没有线程在该内存位置写入未排序的内存，多个线程读取内存就不是数据竞争。
这种情况可能被排除在数据竞争的描述之外，因为这种情况不是数据竞争。
cppreference.com says:
Threads and data races
When an evaluation of an expression writes to a memory location and another evaluation reads or modifies the same memory location, the expressions are said to conflict. A program that has two conflicting evaluations has a data race unless...
这里说的是'thread1-write thread2-read'（W-R）的场景和'thread1-write thread2-write'（W-W）的场景。
'thread1-read thread2-read' (R-R) 呢？
没有。只要没有线程在该内存位置写入未排序的内存，多个线程读取内存就不是数据竞争。
这种情况可能被排除在数据竞争的描述之外，因为这种情况不是数据竞争。