Re: [PATCH v2 03/13] rust: lock: introduce `Mutex`

Peter Zijlstra
2023-04-05T20:31:21Z

On Wed, Apr 05, 2023 at 05:21:44PM -0300, Wedson Almeida Filho wrote:
> On Wed, Apr 05, 2023 at 09:18:26PM +0200, Peter Zijlstra wrote:
> > On Wed, Apr 05, 2023 at 08:04:22PM +0200, Greg KH wrote:
> > > On Wed, Apr 05, 2023 at 08:03:11PM +0200, Greg KH wrote:
> > > > On Wed, Apr 05, 2023 at 02:51:01PM -0300, Wedson Almeida Filho wrote:
> > > > > +void rust_helper_mutex_lock(struct mutex *lock)
> > > > > +{
> > > > > + mutex_lock(lock);
> > > > > +}
> > > > > +EXPORT_SYMBOL_GPL(rust_helper_mutex_lock);
> > > > > +
> > > >
> > > > No need to ever unlock a mutex?
> > >
> > > Oh nevermind, mutex_lock() is a macro, mutex_unlock() is not...
> >
> > Yeah, so I despise all these stupid helpers... but I suppose it's the
> > best they could come up with to interface the languages :/
> >
> > The only hope is that the thing can do cross-language LTO or something
> > to re-inline stuff.
>
> One thing we could to do improve the situation is to convert some of the
> existing macros into inline functions on the header files.
>
> We can't do it for all cases (e.g., cases like mutex_init that declare a new
> static variable when lockdep is enabled) but mutex_lock is just a function
> when lockdep is disabled, and just calls mutex_lock_nested() when it is enabled.
>
> How do you feel about this?
>
> -#define mutex_lock(lock) mutex_lock_nested(lock, 0)
> +static inline void mutex_lock(struct mutex *lock)
> +{
> + mutex_lock_nested(lock, 0);
> +}

Can rust actually parse C headers and inline C functions ? I thought the
whole problem was that it can only call C ABI symbols (which inline
functions are not).