Re: [PATCH RFC] tools/memory-model: Adjust ctrl dependency definition

From: Alan Stern
Date: Fri Jul 15 2022 - 09:27:38 EST

On Fri, Jul 15, 2022 at 02:27:28PM +0200, Paul Heidekrüger wrote:
> I have just been thinking about how to word this patch; am I correct in
> assuming that the LKMM does not deal with loop conditions? Or in other
> words, there is no way for a loop condition to impose a ctrl dependency on
> any WRITE_ONCE's in the loop body? It are only if and switch statements the
> LKMM is concerned with in the case of ctrl dependencies?

In theory, the LKMM does say that a loop condition imposes a control
dependency on any memory accesses within the loop body. However, the
herd7 tool has only very limited support for looping constructs, so in
practice it's not possible to create suitable litmus tests with loops.