Re: Internal vs. external barriers (was: Re: Interesting LKMM litmus test)

Alan Stern
2023-01-18T17:08:46Z

On Wed, Jan 18, 2023 at 08:59:55AM -0800, Boqun Feng wrote:
> On Wed, Jan 18, 2023 at 11:03:35AM -0500, Alan Stern wrote:
> > On Tue, Jan 17, 2023 at 09:17:04PM -0800, Paul E. McKenney wrote:
> > > On Tue, Jan 17, 2023 at 09:15:15PM -0500, Alan Stern wrote:
> > > > Maybe we don't. Please test the patch below; I think it will do what
> > > > you want -- and it doesn't rule out nesting.
> > >
> > > It works like a champ on manual/kernel/C-srcu*.litmus in the litmus
> > > repository on github, good show and thank you!!!
> > >
> > > I will make more tests, and am checking this against the rest of the
> > > litmus tests in the repo, but in the meantime would you be willing to
> > > have me add your Signed-off-by?
> >
> > I'll email a real patch submission in the not-too-distant future,
> > assuming you don't find any problems with the new code.
>
> I haven't tested the following, but I think we also need it to avoid
> (although rare) mixing srcu_struct with normal memory access?
>
> Since you are working on a patch, I think I better mention this ;-)
>
> Regards,
> Boqun
>
> diff --git a/tools/memory-model/lock.cat b/tools/memory-model/lock.cat
> index 6b52f365d73a..c134c2027224 100644
> --- a/tools/memory-model/lock.cat
> +++ b/tools/memory-model/lock.cat
> @@ -37,7 +37,7 @@ let RU = try RU with emptyset
> let LF = LF | RL
>
> (* There should be no ordinary R or W accesses to spinlocks *)
> -let ALL-LOCKS = LKR | LKW | UL | LF | RU
> +let ALL-LOCKS = LKR | LKW | UL | LF | RU | Srcu-lock | Srcu-unlock
> flag ~empty [M \ IW] ; loc ; [ALL-LOCKS] as mixed-lock-accesses
>
> (* Link Lock-Reads to their RMW-partner Lock-Writes *)

Great point! I'll at this to the patch, thanks.

Alan