Re: [PATCH v7 1/9] rust: Introduce atomic API helpers

On Wed, Jul 16, 2025 at 02:47:13PM +0200, Peter Zijlstra wrote:
> On Wed, Jul 16, 2025 at 11:23:09AM +0200, Greg Kroah-Hartman wrote:
> > On Sun, Jul 13, 2025 at 10:36:48PM -0700, Boqun Feng wrote:
> > > In order to support LKMM atomics in Rust, add rust_helper_* for atomic
> > > APIs. These helpers ensure the implementation of LKMM atomics in Rust is
> > > the same as in C. This could save the maintenance burden of having two
> > > similar atomic implementations in asm.
> > > 
> > > Originally-by: Mark Rutland <[email protected]>
> > > Reviewed-by: Alice Ryhl <[email protected]>
> > > Signed-off-by: Boqun Feng <[email protected]>
> > > ---
> > >  rust/helpers/atomic.c                     | 1040 +++++++++++++++++++++
> > >  rust/helpers/helpers.c                    |    1 +
> > >  scripts/atomic/gen-atomics.sh             |    1 +
> > >  scripts/atomic/gen-rust-atomic-helpers.sh |   67 ++
> > >  4 files changed, 1109 insertions(+)
> > >  create mode 100644 rust/helpers/atomic.c
> > >  create mode 100755 scripts/atomic/gen-rust-atomic-helpers.sh
> > > 
> > > diff --git a/rust/helpers/atomic.c b/rust/helpers/atomic.c
> > > new file mode 100644
> > > index 000000000000..cf06b7ef9a1c
> > > --- /dev/null
> > > +++ b/rust/helpers/atomic.c
> > > @@ -0,0 +1,1040 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +
> > > +// Generated by scripts/atomic/gen-rust-atomic-helpers.sh
> > > +// DO NOT MODIFY THIS FILE DIRECTLY
> > 
> > As this is auto-generated, how do we know when to auto-generate it
> > again?  What files does it depend on?  And why can't we just
> > auto-generate it at build time instead of having a static file in the
> > tree that no one knows when to regenerate it?  :)
> 
> It depends on the scripts/atomic/* bits. They hardly if ever change. We
> do it this way because:
> 
>  - generating these files every build is 'slow'-ish;
>  - code navigation suffers;
>  - Linus asked for this.
> 
> Specifically, pretty much the entire atomic_*() namespace would
> disappear from ctags / code-browsing-tool-of-choice if we would not
> check in these files.

Ah, ok, that makes sense in a sad way.  As long as someone knows to
regenerate these files when needed, hopefully when the C files change
someone knows to update these rust ones...

thanks,

greg k-h