Re: [PATCH v6 03/14] PM: Introduce an Energy Model management framework

[Quentin Perret]

Hi Andrea,

On Tuesday 11 Sep 2018 at 11:34:56 (+0200), Andrea Parri wrote:
> FYI, the directory "tools/memory-model/" provides an "automated
> memory-barriers.txt": in short, you encode your "memory ordering
> questions" into "litmus tests" to be passed to the tool/simulator;
> the tool will then answer with "Yes/No" (plus other information).
> 
> Some preparation is required to set up and learn how to use the
> LKMM tools, but once there, I expect them to be more "efficient"
> than reading memory-barriers.txt... ;-)

Thanks for pointing this out, I'll have a look.

> Please don't hesitate
> to contact me/the LKMM maintainers if you need help with this.

And thanks for that too.

> You'd need some info in order to write down a _well-formed litmus
> test, e.g., matching barrier/synchronization and interested memory
> accesses on the reader side (IAC, the replacement "store-release
> -> store-once+smp_wmb" discussed above is suspicious...).

Regarding the disccusion above, I was actually planning on removing the
smp_wmb entirely and rely on WRITE_ONCE + mutex_{un}lock here. Do you
see something obviously wrong with that ?

I guess the LKMM tools should give me the yes/no answer I want, but if
that's a no, I'd also like to understand why ... :-)

Thanks,
Quentin