What is the logic of Volatile.Read and Volatile.Write?

Question

From MSDN Volatile.Read():

Reads a field value. On systems that require this, a memory barrier is inserted that prevents the processor from reordering the following operations: If reading or writing code appears after this method, the processor cannot move it before this method.

and Volatile.Write():

Writes a value to a field. On systems that require this, a memory barrier is inserted that prevents the processor from reordering the following operations: if a reading appears before this method or writing to the code, the processor cannot move it after this method.

I think I can understand the use cases Volatile.Read()and Volatile.Write(), and I saw many examples explaining why these two methods help to ensure the correctness of the program.

But I still wonder what the logic of these rules is.

Take, Volatile.Read()as an example, why it requires operations after , it cannot be moved before , but does not require anything from operations before that?

And why is it the opposite Volatile.Write()?

Thank!

Answer 1

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Answer 2

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