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McKenney" , "Liam R. Howlett" , Gary Guo , Miguel Ojeda , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Trevor Gross , Danilo Krummrich , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Uladzislau Rezki , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Andrew Ballance , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH RFC 0/2] rcu box container for Rust + maple tree load_rcu Message-ID: References: <20260116-rcu-box-v1-0-38ebfbcd53f0@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: nq5tj1qsxmi7yifmurutfob7ckkrq4m8 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 6226620003 X-Rspam-User: X-HE-Tag: 1768664391-643541 X-HE-Meta: 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 XZp5Sdef 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 will call synchronize_rcu() before dropping > `P`. And I think we can have an asynchronous drop pointer type like > `RcuOld` that requires `P` is a type like `Box`, One blocker on that is Drop impls cannot be specialized. We probably need a different pointer type like RcuOldAsync... Regards, Boqun > and the drop of `RcuOld, Async>` would be `call_rcu()` > or `kfree_rcu()`. > > Regards, > Boqun > > > Alice