linux-kernel - Re: [PATCH RFC 0/2] rcu box container for Rust + maple tree load

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] [day] [month] [year] [list]

Message-Id: <DFR0M1EO7KHO.2SQJO7S2NXC3P@garyguo.net>
Date: Sat, 17 Jan 2026 16:46:12 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Boqun Feng" <boqun.feng@...il.com>, "Alice Ryhl" <aliceryhl@...gle.com>
Cc: "Paul E. McKenney" <paulmck@...nel.org>, "Liam R. Howlett"
 <Liam.Howlett@...cle.com>, "Gary Guo" <gary@...yguo.net>, "Miguel Ojeda"
 <ojeda@...nel.org>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, "Benno Lossin" <lossin@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Trevor Gross" <tmgross@...ch.edu>,
 "Danilo Krummrich" <dakr@...nel.org>, "Frederic Weisbecker"
 <frederic@...nel.org>, "Neeraj Upadhyay" <neeraj.upadhyay@...nel.org>,
 "Joel Fernandes" <joelagnelf@...dia.com>, "Josh Triplett"
 <josh@...htriplett.org>, "Uladzislau Rezki" <urezki@...il.com>, "Steven
 Rostedt" <rostedt@...dmis.org>, "Mathieu Desnoyers"
 <mathieu.desnoyers@...icios.com>, "Lai Jiangshan" <jiangshanlai@...il.com>,
 "Zqiang" <qiang.zhang@...ux.dev>, "Andrew Ballance"
 <andrewjballance@...il.com>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <rcu@...r.kernel.org>,
 <maple-tree@...ts.infradead.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH RFC 0/2] rcu box container for Rust + maple tree
 load_rcu

On Sat Jan 17, 2026 at 3:39 PM GMT, Boqun Feng wrote:
> On Sat, Jan 17, 2026 at 10:05:18PM +0800, Boqun Feng wrote:
>> On Sat, Jan 17, 2026 at 01:29:25PM +0000, Alice Ryhl wrote:
>> > On Sat, Jan 17, 2026 at 09:11:49PM +0800, Boqun Feng wrote:
>> > > In Rcu + RcuOld design, RcuBox is just a Box
>> > > because these two pointer types handle reclaim + accesses.
>> > 
>> > How would that work? Dropping my RcuBox<_> must use kfree_rcu() or
>> > synchronize_rcu() or it is unsound. So it can't just be a Box.
>> > 
>> 
>> RcuOld<P: ForeignOwnable> will call synchronize_rcu() before dropping
>> `P`. And I think we can have an asynchronous drop pointer type like
>> `RcuOld<P, Async>` that requires `P` is a type like `Box<HasRcuHead>`,
>
> One blocker on that is Drop impls cannot be specialized. We probably
> need a different pointer type like RcuOldAsync...

I won't be too worried on this apsect, you could just branch on a const in the
drop function.

Alternatively, we can have a method like this

impl<T: HasRcuHead> RcuOld<Box<T>> {
    fn drop_async(self) {
        // do call_rcu
    }
}

Best,
Gary