Add an iterator for `Cpumask` making use of C's `cpumask_next`.
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
---
rust/helpers/cpumask.c | 5 +++++
rust/kernel/cpumask.rs | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 52 insertions(+), 1 deletion(-)
diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c
index eb10598a0242..d95bfa111191 100644
--- a/rust/helpers/cpumask.c
+++ b/rust/helpers/cpumask.c
@@ -42,6 +42,11 @@ bool rust_helper_cpumask_full(struct cpumask *srcp)
return cpumask_full(srcp);
}
+unsigned int rust_helper_cpumask_next(int n, struct cpumask *srcp)
+{
+ return cpumask_next(n, srcp);
+}
+
unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)
{
return cpumask_weight(srcp);
diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
index 3fcbff438670..b7401848f59e 100644
--- a/rust/kernel/cpumask.rs
+++ b/rust/kernel/cpumask.rs
@@ -6,7 +6,7 @@
use crate::{
alloc::{AllocError, Flags},
- cpu::CpuId,
+ cpu::{self, CpuId},
prelude::*,
types::Opaque,
};
@@ -161,6 +161,52 @@ pub fn copy(&self, dstp: &mut Self) {
}
}
+/// Iterator for a `Cpumask`.
+pub struct CpumaskIter<'a> {
+ mask: &'a Cpumask,
+ last: Option<u32>,
+}
+
+impl<'a> CpumaskIter<'a> {
+ /// Creates a new `CpumaskIter` for the given `Cpumask`.
+ fn new(mask: &'a Cpumask) -> CpumaskIter<'a> {
+ Self { mask, last: None }
+ }
+}
+
+impl<'a> Iterator for CpumaskIter<'a> {
+ type Item = CpuId;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ // SAFETY: By the type invariant, `self.mask.as_raw` is a `struct cpumask *`.
+ let next = unsafe {
+ bindings::cpumask_next(
+ if let Some(last) = self.last {
+ last.try_into().unwrap()
+ } else {
+ -1
+ },
+ self.mask.as_raw(),
+ )
+ };
+
+ if next == cpu::nr_cpu_ids() {
+ None
+ } else {
+ self.last = Some(next);
+ // SAFETY: `cpumask_next` returns either `nr_cpu_ids` or a valid CPU ID.
+ unsafe { Some(CpuId::from_u32_unchecked(next)) }
+ }
+ }
+}
+
+impl Cpumask {
+ /// Returns an iterator over the set bits in the cpumask.
+ pub fn iter(&self) -> CpumaskIter<'_> {
+ CpumaskIter::new(self)
+ }
+}
+
/// A CPU Mask pointer.
///
/// Rust abstraction for the C `struct cpumask_var_t`.
--
2.34.1On Wed, Nov 05, 2025 at 03:01:13PM -0800, Mitchell Levy wrote:
> Add an iterator for `Cpumask` making use of C's `cpumask_next`.
>
> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
> ---
> rust/helpers/cpumask.c | 5 +++++
> rust/kernel/cpumask.rs | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c
> index eb10598a0242..d95bfa111191 100644
> --- a/rust/helpers/cpumask.c
> +++ b/rust/helpers/cpumask.c
> @@ -42,6 +42,11 @@ bool rust_helper_cpumask_full(struct cpumask *srcp)
> return cpumask_full(srcp);
> }
>
> +unsigned int rust_helper_cpumask_next(int n, struct cpumask *srcp)
> +{
> + return cpumask_next(n, srcp);
> +}
> +
> unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)
> {
> return cpumask_weight(srcp);
> diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
> index 3fcbff438670..b7401848f59e 100644
> --- a/rust/kernel/cpumask.rs
> +++ b/rust/kernel/cpumask.rs
> @@ -6,7 +6,7 @@
>
> use crate::{
> alloc::{AllocError, Flags},
> - cpu::CpuId,
> + cpu::{self, CpuId},
> prelude::*,
> types::Opaque,
> };
> @@ -161,6 +161,52 @@ pub fn copy(&self, dstp: &mut Self) {
> }
> }
>
> +/// Iterator for a `Cpumask`.
> +pub struct CpumaskIter<'a> {
> + mask: &'a Cpumask,
> + last: Option<u32>,
This is not the last, it's a current CPU.
> +}
> +
> +impl<'a> CpumaskIter<'a> {
> + /// Creates a new `CpumaskIter` for the given `Cpumask`.
> + fn new(mask: &'a Cpumask) -> CpumaskIter<'a> {
> + Self { mask, last: None }
> + }
> +}
> +
> +impl<'a> Iterator for CpumaskIter<'a> {
> + type Item = CpuId;
> +
> + fn next(&mut self) -> Option<Self::Item> {
> + // SAFETY: By the type invariant, `self.mask.as_raw` is a `struct cpumask *`.
> + let next = unsafe {
> + bindings::cpumask_next(
> + if let Some(last) = self.last {
> + last.try_into().unwrap()
> + } else {
> + -1
> + },
> + self.mask.as_raw(),
> + )
> + };
> +
> + if next == cpu::nr_cpu_ids() {
> + None
Please: if next >= cpu::nr_cpu_ids() {
> + } else {
> + self.last = Some(next);
> + // SAFETY: `cpumask_next` returns either `nr_cpu_ids` or a valid CPU ID.
Now that you've handled the no-found case in the previous block, the
comment doesn't look correct. Can you either move it on top of the
if-else, or just drop entirely?
> + unsafe { Some(CpuId::from_u32_unchecked(next)) }
> + }
> + }
> +}
> +
> +impl Cpumask {
> + /// Returns an iterator over the set bits in the cpumask.
> + pub fn iter(&self) -> CpumaskIter<'_> {
> + CpumaskIter::new(self)
> + }
> +}
> +
> /// A CPU Mask pointer.
> ///
> /// Rust abstraction for the C `struct cpumask_var_t`.
>
> --
> 2.34.1
On Thu, Nov 06, 2025 at 07:25:27PM -0500, Yury Norov wrote:
> On Wed, Nov 05, 2025 at 03:01:13PM -0800, Mitchell Levy wrote:
> > Add an iterator for `Cpumask` making use of C's `cpumask_next`.
> >
> > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
> > ---
> > rust/helpers/cpumask.c | 5 +++++
> > rust/kernel/cpumask.rs | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 52 insertions(+), 1 deletion(-)
> >
> > diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c
> > index eb10598a0242..d95bfa111191 100644
> > --- a/rust/helpers/cpumask.c
> > +++ b/rust/helpers/cpumask.c
> > @@ -42,6 +42,11 @@ bool rust_helper_cpumask_full(struct cpumask *srcp)
> > return cpumask_full(srcp);
> > }
> >
> > +unsigned int rust_helper_cpumask_next(int n, struct cpumask *srcp)
> > +{
> > + return cpumask_next(n, srcp);
> > +}
> > +
> > unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)
> > {
> > return cpumask_weight(srcp);
> > diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
> > index 3fcbff438670..b7401848f59e 100644
> > --- a/rust/kernel/cpumask.rs
> > +++ b/rust/kernel/cpumask.rs
> > @@ -6,7 +6,7 @@
> >
> > use crate::{
> > alloc::{AllocError, Flags},
> > - cpu::CpuId,
> > + cpu::{self, CpuId},
> > prelude::*,
> > types::Opaque,
> > };
> > @@ -161,6 +161,52 @@ pub fn copy(&self, dstp: &mut Self) {
> > }
> > }
> >
> > +/// Iterator for a `Cpumask`.
> > +pub struct CpumaskIter<'a> {
> > + mask: &'a Cpumask,
> > + last: Option<u32>,
>
> This is not the last, it's a current CPU.
Ah, I meant it in the sense of "the last cpuid we've seen", though now
that you point it out I agree the naming here is poor. Will correct to
`current`.
> > +}
> > +
> > +impl<'a> CpumaskIter<'a> {
> > + /// Creates a new `CpumaskIter` for the given `Cpumask`.
> > + fn new(mask: &'a Cpumask) -> CpumaskIter<'a> {
> > + Self { mask, last: None }
> > + }
> > +}
> > +
> > +impl<'a> Iterator for CpumaskIter<'a> {
> > + type Item = CpuId;
> > +
> > + fn next(&mut self) -> Option<Self::Item> {
> > + // SAFETY: By the type invariant, `self.mask.as_raw` is a `struct cpumask *`.
> > + let next = unsafe {
> > + bindings::cpumask_next(
> > + if let Some(last) = self.last {
> > + last.try_into().unwrap()
> > + } else {
> > + -1
> > + },
> > + self.mask.as_raw(),
> > + )
> > + };
> > +
> > + if next == cpu::nr_cpu_ids() {
> > + None
>
> Please: if next >= cpu::nr_cpu_ids() {
>
> > + } else {
> > + self.last = Some(next);
> > + // SAFETY: `cpumask_next` returns either `nr_cpu_ids` or a valid CPU ID.
>
> Now that you've handled the no-found case in the previous block, the
> comment doesn't look correct. Can you either move it on top of the
> if-else, or just drop entirely?
Actually, now that I'm looking at this again, I think this whole if-else
thing should just be:
```
CpuId::from_u32(next)
```
which does exactly what we want here. I think this should address both
of your concerns, though please let me know if it doesn't.
Thanks,
Mitchell
> > + unsafe { Some(CpuId::from_u32_unchecked(next)) }
> > + }
> > + }
> > +}
> > +
> > +impl Cpumask {
> > + /// Returns an iterator over the set bits in the cpumask.
> > + pub fn iter(&self) -> CpumaskIter<'_> {
> > + CpumaskIter::new(self)
> > + }
> > +}
> > +
> > /// A CPU Mask pointer.
> > ///
> > /// Rust abstraction for the C `struct cpumask_var_t`.
> >
> > --
> > 2.34.1
On Fri, Nov 07, 2025 at 04:06:19PM -0800, Mitchell Levy wrote:
> On Thu, Nov 06, 2025 at 07:25:27PM -0500, Yury Norov wrote:
> > On Wed, Nov 05, 2025 at 03:01:13PM -0800, Mitchell Levy wrote:
> > > Add an iterator for `Cpumask` making use of C's `cpumask_next`.
> > >
> > > Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
> > > Signed-off-by: Mitchell Levy <levymitchell0@gmail.com>
> > > ---
> > > rust/helpers/cpumask.c | 5 +++++
> > > rust/kernel/cpumask.rs | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
> > > 2 files changed, 52 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c
> > > index eb10598a0242..d95bfa111191 100644
> > > --- a/rust/helpers/cpumask.c
> > > +++ b/rust/helpers/cpumask.c
> > > @@ -42,6 +42,11 @@ bool rust_helper_cpumask_full(struct cpumask *srcp)
> > > return cpumask_full(srcp);
> > > }
> > >
> > > +unsigned int rust_helper_cpumask_next(int n, struct cpumask *srcp)
> > > +{
> > > + return cpumask_next(n, srcp);
> > > +}
> > > +
> > > unsigned int rust_helper_cpumask_weight(struct cpumask *srcp)
> > > {
> > > return cpumask_weight(srcp);
> > > diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
> > > index 3fcbff438670..b7401848f59e 100644
> > > --- a/rust/kernel/cpumask.rs
> > > +++ b/rust/kernel/cpumask.rs
> > > @@ -6,7 +6,7 @@
> > >
> > > use crate::{
> > > alloc::{AllocError, Flags},
> > > - cpu::CpuId,
> > > + cpu::{self, CpuId},
> > > prelude::*,
> > > types::Opaque,
> > > };
> > > @@ -161,6 +161,52 @@ pub fn copy(&self, dstp: &mut Self) {
> > > }
> > > }
> > >
> > > +/// Iterator for a `Cpumask`.
> > > +pub struct CpumaskIter<'a> {
> > > + mask: &'a Cpumask,
> > > + last: Option<u32>,
> >
> > This is not the last, it's a current CPU.
>
> Ah, I meant it in the sense of "the last cpuid we've seen", though now
> that you point it out I agree the naming here is poor. Will correct to
> `current`.
>
> > > +}
> > > +
> > > +impl<'a> CpumaskIter<'a> {
> > > + /// Creates a new `CpumaskIter` for the given `Cpumask`.
> > > + fn new(mask: &'a Cpumask) -> CpumaskIter<'a> {
> > > + Self { mask, last: None }
> > > + }
> > > +}
> > > +
> > > +impl<'a> Iterator for CpumaskIter<'a> {
> > > + type Item = CpuId;
> > > +
> > > + fn next(&mut self) -> Option<Self::Item> {
> > > + // SAFETY: By the type invariant, `self.mask.as_raw` is a `struct cpumask *`.
> > > + let next = unsafe {
> > > + bindings::cpumask_next(
> > > + if let Some(last) = self.last {
> > > + last.try_into().unwrap()
> > > + } else {
> > > + -1
> > > + },
> > > + self.mask.as_raw(),
> > > + )
> > > + };
> > > +
> > > + if next == cpu::nr_cpu_ids() {
> > > + None
> >
> > Please: if next >= cpu::nr_cpu_ids() {
> >
> > > + } else {
> > > + self.last = Some(next);
> > > + // SAFETY: `cpumask_next` returns either `nr_cpu_ids` or a valid CPU ID.
> >
> > Now that you've handled the no-found case in the previous block, the
> > comment doesn't look correct. Can you either move it on top of the
> > if-else, or just drop entirely?
>
> Actually, now that I'm looking at this again, I think this whole if-else
> thing should just be:
> ```
> CpuId::from_u32(next)
> ```
> which does exactly what we want here. I think this should address both
> of your concerns, though please let me know if it doesn't.
Looks like that.
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