Will two READ_ONCE()s in a row execute in order

Valentin Vidić vvidic at valentin-vidic.from.hr
Mon Oct 25 05:37:37 EDT 2021

On Mon, Oct 25, 2021 at 04:32:41PM +0800, Zhang Zeren wrote:
> It seems that these two READ_ONCE()s can be executed in any order. But if I
> run this test in a x86 machine, which has a more strict memory model,
> result 1:r0=1; 1:r1=0; disappears. So the order depends on the memory model
> provided by the CPU architecture? Isn't this contradicted with
> memory-barrier.txt?

The documentation example has two memory acceses where the second uses
the value from the first one, so they are order dependent:


In your example there seems to be no dependency between x and y so they
could be reordered?


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