Re: [PATCH] lockdep: avoid struct return in lock_stats()

[Boqun Feng <boqun.feng@gmail.com>]

On Wed, Jun 18, 2025 at 08:51:07PM +0300, Andy Shevchenko wrote:
> On Tue, Jun 17, 2025 at 10:17:32PM -0700, Boqun Feng wrote:
> > On Tue, Jun 10, 2025 at 11:29:21AM +0200, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@arndb.de>
> > > 
> > > Returning a large structure from the lock_stats() function causes clang
> > > to have multiple copies of it on the stack and copy between them, which
> > > can end up exceeding the frame size warning limit:
> > > 
> > > kernel/locking/lockdep.c:300:25: error: stack frame size (1464) exceeds limit (1280) in 'lock_stats' [-Werror,-Wframe-larger-than]
> > >   300 | struct lock_class_stats lock_stats(struct lock_class *class)
> > > 
> > > Change the calling conventions to directly operate on the caller's copy,
> > > which apparently is what gcc does already.
> > > 
> > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > 
> > Queued for more tests and reviews, thanks!
> 
> What about this one:
>     lockdep: change 'static const' variables to enum values
> 
> ?
> 
> (I can't quickly find the pointer right now, but I think in lore.kernel.org you can find it)
> 

This one:

	https://lore.kernel.org/lkml/20250409122314.2848028-6-arnd@kernel.org/

? I will take a look (give me some time to learn about that compiler
option), but seems trivial enough, should be in the next merge window if
no problem found. Thanks for bringing it up.

Regards,
Boqun

> -- 
> With Best Regards,
> Andy Shevchenko
> 
>