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

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Message-ID: <87cy2iosv3.fsf@t14s.mail-host-address-is-not-set>
Date: Fri, 06 Feb 2026 15:21:20 +0100
From: Andreas Hindborg <a.hindborg@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
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

Alice Ryhl <aliceryhl@...gle.com> writes:

> 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.

Ok.

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

I don't think coding a custom helper in C is better than open codng the
initalization in rust?


Best regards,
Andreas Hindborg