linux-kernel - Re: [PATCH v1 2/2] rust: Add read_poll

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Message-ID: <87y0rqf844.fsf@t14s.mail-host-address-is-not-set>
Date: Mon, 11 Aug 2025 12:47:07 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: FUJITA Tomonori <fujita.tomonori@...il.com>, alex.gaynor@...il.com,
 ojeda@...nel.org
Cc: aliceryhl@...gle.com, anna-maria@...utronix.de,
 bjorn3_gh@...tonmail.com, boqun.feng@...il.com, dakr@...nel.org,
 frederic@...nel.org, gary@...yguo.net, jstultz@...gle.com,
 linux-kernel@...r.kernel.org, lossin@...nel.org, lyude@...hat.com,
 rust-for-linux@...r.kernel.org, sboyd@...nel.org, tglx@...utronix.de,
 tmgross@...ch.edu, acourbot@...dia.com, daniel.almeida@...labora.com,
 Fiona Behrens <me@...enk.dev>
Subject: Re: [PATCH v1 2/2] rust: Add read_poll_timeout functions

"FUJITA Tomonori" <fujita.tomonori@...il.com> writes:

> Add read_poll_timeout functions which poll periodically until a
> condition is met or a timeout is reached.
>
> The C's read_poll_timeout (include/linux/iopoll.h) is a complicated
> macro and a simple wrapper for Rust doesn't work. So this implements
> the same functionality in Rust.
>
> The C version uses usleep_range() while the Rust version uses
> fsleep(), which uses the best sleep method so it works with spans that
> usleep_range() doesn't work nicely with.
>
> The sleep_before_read argument isn't supported since there is no user
> for now. It's rarely used in the C version.
>
> read_poll_timeout() can only be used in a nonatomic context. This
> requirement is not checked by these abstractions, but it is intended
> that klint [1] or a similar tool will be used to check it in the
> future.
>
> Link: https://rust-for-linux.com/klint [1]
> Reviewed-by: Fiona Behrens <me@...enk.dev>
> Tested-by: Daniel Almeida <daniel.almeida@...labora.com>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>

With the example removed:

-///
-/// ```rust
-/// use kernel::sync::{SpinLock, new_spinlock};
-/// use kernel::time::Delta;
-/// use kernel::time::poll::read_poll_timeout;
-///
-/// let lock = KBox::pin_init(new_spinlock!(()), kernel::alloc::flags::GFP_KERNEL)?;
-/// let g = lock.lock();
-/// read_poll_timeout(|| Ok(()), |()| true, Delta::from_micros(42), Some(Delta::from_micros(42)));
-/// drop(g);
-///
-/// # Ok::<(), Error>(())
-/// ```

Reviewed-by: Andreas Hindborg <a.hindborg@...nel.org>


Best regards,
Andreas Hindborg