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

[Peter Zijlstra]

On Thu, Mar 30, 2023 at 11:47:12AM -0700, Boqun Feng wrote:
> On Thu, Mar 30, 2023 at 03:01:08PM +0200, Peter Zijlstra wrote:
> > On Thu, Mar 30, 2023 at 01:39:44AM -0300, Wedson Almeida Filho wrote:
> > > From: Wedson Almeida Filho <walmeida@xxxxxxxxxxxxx>
> > > 
> > > This is the `struct mutex` lock backend and allows Rust code to use the
> > > kernel mutex idiomatically.
> > 
> > What, if anything, are the plans to support the various lockdep
> > annotations? Idem for the spinlock thing in the other patch I suppose.
> 
> FWIW:
> 
> *	At the init stage, SpinLock and Mutex in Rust use initializers
> 	that are aware of the lockdep, so everything (lockdep_map and
> 	lock_class) is all set up.
> 
> *	At acquire or release time, Rust locks just use ffi to call C
> 	functions that have lockdep annotations in them, so lockdep
> 	should just work.
> 

ffi is what the C++ world calls RAII ?

But yes, I got that far, but I wondered about things like
spin_lock_nested(&foo, SINGLE_DEPTH_NESTING) and other such 'advanced'
annotations.

Surely we're going to be needing them at some point. I suppose you can
do the single depth nesting one with a special guard type (or whatever
you call that in the rust world) ?