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

[Alice Ryhl <aliceryhl@google.com>]

On Tue, Jun 23, 2026 at 04:55:31PM +0100, Gary Guo wrote:
> 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@google.com>
> > ---
> >  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@garyguo.net/
> , 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");

I did it this way for consistency with the existing pr_*_once!.

Alice