Re: [PATCH 01/31] rhashtable: Allow rhashtable to be used from irq-safe contexts

[Tejun Heo]

Hello,

On Wed, Nov 30, 2022 at 08:35:13AM -0800, Linus Torvalds wrote:
> On Wed, Nov 30, 2022 at 12:23 AM Tejun Heo <tj@xxxxxxxxxx> wrote:
> >
> >
> >  static inline void rht_lock(struct bucket_table *tbl,
> > -                           struct rhash_lock_head __rcu **bkt)
> > +                           struct rhash_lock_head __rcu **bkt,
> > +                           unsigned long *flags)
> 
> I guess it doesn't matter as long as this actually gets inlined, but
> wouldn't it be better to have
> 
>    flags = rht_lock(..);
>    ...
>    rht_unlock(.., flags);
> 
> as the calling convention? Rather than passing a pointer to the stack around.

Sure thing.

> That's what the native _raw_spin_lock_irqsave() interface is (even if
> "spin_lock_irqsave()" itself for historical reasons uses that inline
> asm-like "pass argument by reference *without* using a pointer")

Yeah, it always feels kinda weird to wrap irqsave/restore due to the special
reference passing.

> And gaah, we should have made 'flags' be a real type long ago, but I
> guess 'unsigned long' is too ingrained and traditional to change that
> now.

Hahaha, that's gonna be an epic patchset.

Thanks.

-- 
tejun