[PATCH 3/4] cpumask: add cpumask_{first,next}_andnot() API

Yury Norov
2025-04-07T15:39:03Z

From: Yury Norov [NVIDIA] <yury.norov@gmail.com>

With the lack of the functions, client code has to abuse less efficient
cpumask_nth().

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
---
include/linux/cpumask.h | 59 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 59 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 0f816092c891..9067c3411cd0 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -178,6 +178,19 @@ unsigned int cpumask_first_and(const struct cpumask *srcp1, const struct cpumask
return find_first_and_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
}

+/**
+ * cpumask_first_andnot - return the first cpu from *srcp1 & ~*srcp2
+ * @srcp1: the first input
+ * @srcp2: the second input
+ *
+ * Return: >= nr_cpu_ids if no such cpu found.
+ */
+static __always_inline
+unsigned int cpumask_first_andnot(const struct cpumask *srcp1, const struct cpumask *srcp2)
+{
+ return find_first_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
+}
+
/**
* cpumask_first_and_and - return the first cpu from *srcp1 & *srcp2 & *srcp3
* @srcp1: the first input
@@ -284,6 +297,25 @@ unsigned int cpumask_next_and(int n, const struct cpumask *src1p,
small_cpumask_bits, n + 1);
}

+/**
+ * cpumask_next_andnot - get the next cpu in *src1p & ~*src2p
+ * @n: the cpu prior to the place to search (i.e. return will be > @n)
+ * @src1p: the first cpumask pointer
+ * @src2p: the second cpumask pointer
+ *
+ * Return: >= nr_cpu_ids if no further cpus set in both.
+ */
+static __always_inline
+unsigned int cpumask_next_andnot(int n, const struct cpumask *src1p,
+ const struct cpumask *src2p)
+{
+ /* -1 is a legal arg here. */
+ if (n != -1)
+ cpumask_check(n);
+ return find_next_andnot_bit(cpumask_bits(src1p), cpumask_bits(src2p),
+ small_cpumask_bits, n + 1);
+}
+
/**
* cpumask_next_and_wrap - get the next cpu in *src1p & *src2p, starting from
* @n+1. If nothing found, wrap around and start from
@@ -458,6 +490,33 @@ unsigned int cpumask_any_and_but(const struct cpumask *mask1,
return cpumask_next_and(cpu, mask1, mask2);
}

+/**
+ * cpumask_andnot_any_but - pick an arbitrary cpu from *mask1 & ~*mask2, but not this one.
+ * @mask1: the first input cpumask
+ * @mask2: the second input cpumask
+ * @cpu: the cpu to ignore
+ *
+ * If @cpu == -1, the function returns the first matching cpu.
+ * Returns >= nr_cpu_ids if no cpus set.
+ */
+static __always_inline
+unsigned int cpumask_andnot_any_but(const struct cpumask *mask1,
+ const struct cpumask *mask2,
+ unsigned int cpu)
+{
+ unsigned int i;
+
+ /* -1 is a legal arg here. */
+ if (cpu != -1)
+ cpumask_check(cpu);
+
+ i = cpumask_first_andnot(mask1, mask2);
+ if (i != cpu)
+ return i;
+
+ return cpumask_next_andnot(cpu, mask1, mask2);
+}
+
/**
* cpumask_nth - get the Nth cpu in a cpumask
* @srcp: the cpumask pointer
--
2.43.0