netdev - Re: [PATCH net-next v7 1/5] rust: core abstractions for network PHY drivers

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Date: Wed, 22 Nov 2023 10:16:44 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: tmgross@...ch.edu, andrew@...n.ch, gregkh@...uxfoundation.org,
	aliceryhl@...gle.com, benno.lossin@...ton.me,
	miguel.ojeda.sandonis@...il.com, netdev@...r.kernel.org,
	rust-for-linux@...r.kernel.org, wedsonaf@...il.com
Subject: Re: [PATCH net-next v7 1/5] rust: core abstractions for network PHY
 drivers

On Tue, Nov 21, 2023 at 11:13:06AM +0900, FUJITA Tomonori wrote:
[...]
> 
> I'm not sure we discussed but making DriverVTable Sync works.
> 
> #[repr(transparent)]
> pub struct DriverVTable(Opaque<bindings::phy_driver>);
> 
> // SAFETY: DriverVTable has no &self methods, so immutable references to it are useless.

Minor nitpicking, I would add one more sentense in the safety comment:

	therefore it's safe to share immutable references between
	threads.

or 
	therefore it's safe to share immutable references between
	execution contexts.

once we decide the term here ;-)

The reason is to match Sync definition [1]:

"""
Types for which it is safe to share references between threads.

This trait is automatically implemented when the compiler determines
it’s appropriate.

The precise definition is: a type T is Sync if and only if &T is Send.
In other words, if there is no possibility of undefined behavior
(including data races) when passing &T references between threads.
"""

[1]: https://doc.rust-lang.org/std/marker/trait.Sync.html

Regards,
Boqun

> unsafe impl Sync for DriverVTable {}
> 
> 
> looks correct?
>