From: Boqun Feng <boqun@kernel.org>
To: Alice Ryhl <aliceryhl@google.com>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Carlos Llamas" <cmllamas@google.com>,
"Christian Brauner" <brauner@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
"Alexander Viro" <viro@zeniv.linux.org.uk>,
"Jan Kara" <jack@suse.cz>, "Miguel Ojeda" <ojeda@kernel.org>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Gary Guo" <gary@garyguo.net>,
linux-fsdevel@vger.kernel.org, rust-for-linux@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 1/2] rust: poll: use kfree_rcu() for PollCondVar
Date: Fri, 10 Jul 2026 07:23:06 -0700 [thread overview]
Message-ID: <alEASpx0UvbYnxqy@tardis.local> (raw)
In-Reply-To: <20260707-upgrade-poll-v6-1-4b8fae7bf1d9@google.com>
On Tue, Jul 07, 2026 at 10:43:12AM +0000, Alice Ryhl wrote:
> Rust Binder currently uses PollCondVar, but it calls synchronize_rcu()
> in the destructor, which we would like to avoid. Add a variation of
> PollCondVar that kfree_rcu() instead.
>
> One could avoid the `rcu` field and allocate the rcu_head on drop using
> a fallback to synchronize_rcu() on ENOMEM. However, I'd prefer to avoid
> the potential for synchronize_rcu(), and Binder will only use this for a
> small fraction of processes, so even if it changes which kmalloc bucket
> it falls into, the extra memory is not a problem.
>
> Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Let's switch to a better abstraction like RcuFreeBox later, but I don't
see any issue of this approach in general.
Reviewed-by: Boqun Feng <boqun@kernel.org>
Regards,
Boqun
> ---
> rust/kernel/sync/poll.rs | 73 +++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 72 insertions(+), 1 deletion(-)
>
[..]
next prev parent reply other threads:[~2026-07-10 14:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-07 10:43 [PATCH v6 0/2] Avoid synchronize_rcu() for every thread drop in Rust Binder Alice Ryhl
2026-07-07 10:43 ` [PATCH v6 1/2] rust: poll: use kfree_rcu() for PollCondVar Alice Ryhl
2026-07-10 14:23 ` Boqun Feng [this message]
2026-07-07 10:43 ` [PATCH v6 2/2] rust_binder: move (e)poll wait queue to Process Alice Ryhl
2026-07-11 0:30 ` Boqun Feng
2026-07-11 10:32 ` Alice Ryhl
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