Re: [PATCH 3/5] rust: add pr_*_ratelimit! macros for printing

[Gary Guo]

On Tue Jun 23, 2026 at 4:38 PM BST, Alice Ryhl wrote:
> Printing can be very expensive if it occurs often, so printing that can
> be triggered by userspace should be rate limited. For this purpose, add
> a Rust wrapper around `struct ratelimit_state` and use it in the new
> macros.
>
> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
> ---
>  rust/helpers/helpers.c   |   1 +
>  rust/helpers/ratelimit.c |  14 ++++
>  rust/kernel/lib.rs       |   1 +
>  rust/kernel/prelude.rs   |   8 ++
>  rust/kernel/ratelimit.rs | 202 +++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 226 insertions(+)
>
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index d17eaec76450..2184b11c927f 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -80,6 +80,7 @@
>  #include "processor.c"
>  #include "property.c"
>  #include "pwm.c"
> +#include "ratelimit.c"
>  #include "rbtree.c"
>  #include "rcu.c"
>  #include "refcount.c"
> diff --git a/rust/helpers/ratelimit.c b/rust/helpers/ratelimit.c
> new file mode 100644
> index 000000000000..e5052f568b81
> --- /dev/null
> +++ b/rust/helpers/ratelimit.c
> @@ -0,0 +1,14 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/ratelimit.h>
> +
> +__rust_helper void rust_helper_ratelimit_state_init(struct ratelimit_state *rs,
> +						    int interval, int burst)
> +{
> +	ratelimit_state_init(rs, interval, burst);
> +}
> +
> +__rust_helper void rust_helper_ratelimit_state_exit(struct ratelimit_state *rs)
> +{
> +	ratelimit_state_exit(rs);
> +}
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index b72b2fbe046d..ba65ab4f0b8c 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -111,6 +111,7 @@
>  pub mod ptr;
>  #[cfg(CONFIG_RUST_PWM_ABSTRACTIONS)]
>  pub mod pwm;
> +pub mod ratelimit;
>  pub mod rbtree;
>  pub mod regulator;
>  pub mod revocable;
> diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
> index 44edf72a4a24..5a66028dd973 100644
> --- a/rust/kernel/prelude.rs
> +++ b/rust/kernel/prelude.rs
> @@ -89,13 +89,21 @@
>      },
>      init::InPlaceInit,
>      pr_alert,
> +    pr_alert_ratelimited,
>      pr_crit,
> +    pr_crit_ratelimited,
>      pr_debug,
> +    pr_debug_ratelimited,
>      pr_emerg,
> +    pr_emerg_ratelimited,
>      pr_err,
> +    pr_err_ratelimited,
>      pr_info,
> +    pr_info_ratelimited,
>      pr_notice,
> +    pr_notice_ratelimited,
>      pr_warn,
> +    pr_warn_ratelimited,
>      static_assert,
>      str::CStrExt as _,

I really want this to be just a variant of pr_, not a entire new family of
macros.

Last time I raise this in
https://lore.kernel.org/rust-for-linux/20260108125523.5c7810ae.gary@xxxxxxxxxxx/
, I was suggesting unifying pr_ and dev_ too, which might be a step too much. 

But I think just making ratelimited a keyword in `pr_` macro should be alright?

pr_info!("foo"); // pr_info("foo\n");
pr_info!(once, "foo"); // pr_info_once("foo\n");
pr_info!(ratelimited, "foo"); // pr_info_ratelimited("foo\n");
dev_info!(dev, "foo"); // dev_info(dev, "foo\n");
dev_info!(dev, once, "foo"); // dev_info_once(dev, "foo\n");
dev_info!(dev, ratelimited, "foo"); // dev_info_ratelimited(dev, "foo\n");

Best,
Gary