linux-kernel - Re: [PATCH 10/10] rust: xarray: fix false positive lockdep warnings

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Message-ID: <aXHr5kxJgogHHW1o@google.com>
Date: Thu, 22 Jan 2026 09:20:38 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Tamir Duberstein <tamird@...il.com>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Daniel Gomez <da.gomez@...nel.org>, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/10] rust: xarray: fix false positive lockdep warnings

On Wed, Dec 03, 2025 at 11:26:40PM +0100, Andreas Hindborg wrote:
> Replace the `xa_init_flags` helper with direct initialization of XArray
> structures using `__spin_lock_init`. This allows each XArray to have
> its own lock class key for lockdep, preventing false positive warnings
> about lock ordering violations.
> 
> Add a `new_xarray!` macro that automatically generates a unique lock
> class key for each XArray instantiation site. The macro accepts an
> optional name parameter and uses the `optional_name!` and
> `static_lock_class!` macros to generate appropriate names and lock
> classes.
> 
> Update the `XArray::new` method signature to accept explicit name and
> lock class key parameters. This enables proper lockdep tracking while
> maintaining flexibility for advanced use cases.
> 
> Remove `rust_helper_xa_init_flags` as it is now dead code.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>

IMO this should have a Fixes: tag and probably land separately from the
rest of this series.

There is a similar situation with workqueue, which was solved by using a
custom helper. See rust/helpers/workqueue.c for details.

Alice