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Fri, 10 Apr 2026 14:36:21 -0700 (PDT) From: Mitchell Levy Date: Fri, 10 Apr 2026 14:35:31 -0700 Subject: [PATCH v5 1/8] rust: cpumask: Add a `Cpumask` iterator Precedence: bulk X-Mailing-List: rust-for-linux@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260410-rust-percpu-v5-1-4292380d7a41@gmail.com> References: <20260410-rust-percpu-v5-0-4292380d7a41@gmail.com> In-Reply-To: <20260410-rust-percpu-v5-0-4292380d7a41@gmail.com> To: Miguel Ojeda , Alex Gaynor , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Andrew Morton , Dennis Zhou , Tejun Heo , Christoph Lameter , Danilo Krummrich , Benno Lossin , Yury Norov , Viresh Kumar , Boqun Feng Cc: Tyler Hicks , Allen Pais , linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-mm@kvack.org, Mitchell Levy X-Mailer: b4 0.15.1 X-Developer-Signature: v=1; a=ed25519-sha256; t=1775856978; l=2878; i=levymitchell0@gmail.com; s=20240719; h=from:subject:message-id; bh=BETYXv/iPQABug1OuKQYEFZYT26teVkAoSalVy+DWvg=; b=XwjVmH2pYFv3eafAe1fjdPZKz8H5eTGdm8cmz3xV4HYLP+EHPiCfuzPJVwN/Yjd+JMCLv6Wnp AS9Kw9gl3CcAMjDQbDNlLeQK3O9aaHxYfUQ5eZRr2Un5733dXgLh4dI X-Developer-Key: i=levymitchell0@gmail.com; a=ed25519; pk=n6kBmUnb+UNmjVkTnDwrLwTJAEKUfs2e8E+MFPZI93E= Add an iterator for `Cpumask` making use of C's `cpumask_next`. Acked-by: Viresh Kumar Signed-off-by: Mitchell Levy --- rust/helpers/cpumask.c | 6 ++++++ rust/kernel/cpumask.rs | 51 +++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 56 insertions(+), 1 deletion(-) diff --git a/rust/helpers/cpumask.c b/rust/helpers/cpumask.c index 5deced5b975e..76990e14dfdd 100644 --- a/rust/helpers/cpumask.c +++ b/rust/helpers/cpumask.c @@ -50,6 +50,12 @@ bool rust_helper_cpumask_full(struct cpumask *srcp) return cpumask_full(srcp); } +__rust_helper +unsigned int rust_helper_cpumask_next(int n, struct cpumask *srcp) +{ + return cpumask_next(n, srcp); +} + __rust_helper unsigned int rust_helper_cpumask_weight(struct cpumask *srcp) { diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs index 44bb36636ee3..b74a3fccf4b4 100644 --- a/rust/kernel/cpumask.rs +++ b/rust/kernel/cpumask.rs @@ -14,7 +14,10 @@ #[cfg(CONFIG_CPUMASK_OFFSTACK)] use core::ptr::{self, NonNull}; -use core::ops::{Deref, DerefMut}; +use core::{ + iter::FusedIterator, + ops::{Deref, DerefMut}, +}; /// A CPU Mask. /// @@ -161,6 +164,52 @@ pub fn copy(&self, dstp: &mut Self) { } } +/// Iterator for a `Cpumask`. +pub struct CpumaskIter<'a> { + mask: &'a Cpumask, + /// [`None`] if no bits have been returned yet, or the index of the last bit returned by the + /// iterator. Equal to [`kernel::cpu::nr_cpu_ids()`] when the iterator has been exhausted. + last: Option, +} + +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 { + // cpumask_next WARNs if the first argument is >= nr_cpu_ids when CONFIG_DEBUG_PER_CPU_MAPS + // is set. So, early out in that case + if let Some(last) = self.last { + if last >= kernel::cpu::nr_cpu_ids() { + return None; + } + } + + // SAFETY: By the type invariant, `self.mask.as_raw` is a `struct cpumask *`. + let next = unsafe { + bindings::cpumask_next(self.last.map_or(-1, |l| l as i32), self.mask.as_raw()) + }; + + self.last = Some(next); + CpuId::from_u32(next) + } +} + +impl<'a> FusedIterator for CpumaskIter<'a> {} + +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