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Confused in atomic class: memory_order_relaxed

I am studying this site: https://gcc.gnu.org/wiki/Atomic/GCCMM/AtomicSync , which is very useful for understanding the topic of the atomic class.

But this relaxed example is hard to understand:

    /*Thread 1:*/

    y.store (20, memory_order_relaxed)
    x.store (10, memory_order_relaxed)
    /*Thread 2*/
 if (x.load (memory_order_relaxed) == 10)
      {
        assert (y.load(memory_order_relaxed) == 20) /* assert A */
        y.store (10, memory_order_relaxed)
      }
 /*Thread 3*/
     if (y.load (memory_order_relaxed) == 10)
        assert (x.load(memory_order_relaxed) == 10) /* assert B */

For me, statement B should never fail, since x must be 10 and y = 10 due to the fact that thread 2 is due to this.

But the website says that either the statement in this example can actually CORRECT.

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3 answers

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+1

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y.store (10, memory_order_release);

// thread 3
if (y.load (memory_order_acquire) == 10)

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+4

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+1

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