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

From: Linus Torvalds
Date: Wed Nov 30 2022 - 11:35:58 EST


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.

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")

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.

Linus