linux-kernel - Re: [PATCH v3 3/4] rust: devres: get rid of Devres' inner Arc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <DAWHL4FKR25G.3PFDJX0SGX00E@kernel.org>
Date: Thu, 26 Jun 2025 15:07:47 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Danilo Krummrich" <dakr@...nel.org>
Cc: "Boqun Feng" <boqun.feng@...il.com>, <gregkh@...uxfoundation.org>,
 <rafael@...nel.org>, <ojeda@...nel.org>, <alex.gaynor@...il.com>,
 <gary@...yguo.net>, <bjorn3_gh@...tonmail.com>, <a.hindborg@...nel.org>,
 <aliceryhl@...gle.com>, <tmgross@...ch.edu>, <david.m.ertman@...el.com>,
 <ira.weiny@...el.com>, <leon@...nel.org>, <kwilczynski@...nel.org>,
 <bhelgaas@...gle.com>, <rust-for-linux@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] rust: devres: get rid of Devres' inner Arc

On Thu Jun 26, 2025 at 1:07 PM CEST, Danilo Krummrich wrote:
> On Thu, Jun 26, 2025 at 12:27:18PM +0200, Benno Lossin wrote:
>> On Thu Jun 26, 2025 at 12:01 PM CEST, Danilo Krummrich wrote:
>> > On Wed, Jun 25, 2025 at 09:13:24PM -0700, Boqun Feng wrote:
>> >> On Tue, Jun 24, 2025 at 11:54:01PM +0200, Danilo Krummrich wrote:
>> >> [...]
>> >> > +#[pin_data(PinnedDrop)]
>> >> > +pub struct Devres<T> {
>> >> 
>> >> It makes me realize: I think we need to make `T` being `Send`? Because
>> >> the devm callback can happen on a different thread other than
>> >> `Devres::new()` and the callback may drop `T` because of revoke(), so we
>> >> are essientially sending `T`. Alternatively we can make `Devres::new()`
>> >> and its friend require `T` being `Send`.
>> >> 
>> >> If it's true, we need a separate patch that "Fixes" this.
>> >
>> > Indeed, that needs a fix.
>> 
>> Oh and we have no `'static` bound on `T` either... We should require
>> that as well.
>
> I don't think we actually need that, The Devres instance can't out-live a &T
> passed into it. And the &T can't out-live the &Device<Bound>, hence we're
> guaranteed that devres_callback() is never called because Devres::drop() will be
> able successfully unregister the callback given that we're still in the
> &Device<Bound> scope.

Yeah that's correct, I got confused.

> The only thing that could technically out-live the &Device<Bound> would be
> &'static T, but that would obviously be fine.
>
> Do I miss anything?

Nope :)

---
Cheers,
Benno