Linux doesn't even obey ISO C's Memory Model. Linux was multi-processor many years before ISO C11 documents a Memory Model (the same one as C++ 11) and so it had many years to decide how this stuff should work in practice on actual multi-processor hardware.

https://lwn.net/Articles/718628/

The Linux model and the C++ 11 (as subsequently modified) model are similar in the sense that they respect how the CPU actually works, necessarily in the case of Linux and for practical low level C or C++, but in details they differ, sometimes for good reason and sometimes just because Linux was here first.