linux-kernel - [PATCH v3 6/6] cpumask: Implement cpumask_{first,next}

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Message-Id: <20240830191043.1028827-7-mathieu.desnoyers@efficios.com>
Date: Fri, 30 Aug 2024 15:10:43 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: [PATCH v3 6/6] cpumask: Implement cpumask_{first,next}_{nor,andnot}

Allow finding the first or next bit within two input cpumasks which is
either:

- both zero and zero,
- respectively one and zero.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Yury Norov <yury.norov@...il.com>
Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
---
Changes since v0:
- Rename "notandnot" to "nor".
- Use __always_inline.
Changes since v1:
- Use small_cpumask_bits instead of nr_cpumask_bits, which is better
  optimized for NR_CPUS < BITS_PER_LONG.
---
 include/linux/cpumask.h | 60 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 23686bed441d..0bf6aabae62c 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -204,6 +204,32 @@ unsigned int cpumask_first_and_and(const struct cpumask *srcp1,
 				      cpumask_bits(srcp3), small_cpumask_bits);
 }
 
+/**
+ * cpumask_first_andnot - return the first cpu from *srcp1 & ~*srcp2
+ * @src1p: the first input
+ * @src2p: the second input
+ *
+ * Returns >= nr_cpu_ids if no cpus match in both.
+ */
+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_nor - return the first cpu from ~(*srcp1 | *srcp2)
+ * @src1p: the first input
+ * @src2p: the second input
+ *
+ * Returns >= nr_cpu_ids if no cpus match in both.
+ */
+static __always_inline
+unsigned int cpumask_first_nor(const struct cpumask *srcp1, const struct cpumask *srcp2)
+{
+	return find_first_nor_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits);
+}
+
 /**
  * cpumask_last - get the last CPU in a cpumask
  * @srcp:	- the cpumask pointer
@@ -246,6 +272,40 @@ static inline unsigned int cpumask_next_zero(int n, const struct cpumask *srcp)
 	return find_next_zero_bit(cpumask_bits(srcp), small_cpumask_bits, n+1);
 }
 
+/**
+ * cpumask_next_andnot - return the next cpu from *srcp1 & ~*srcp2
+ * @n: the cpu prior to the place to search (ie. return will be > @n)
+ * @src1p: the first input
+ * @src2p: the second input
+ *
+ * Returns >= nr_cpu_ids if no cpus match in both.
+ */
+static __always_inline
+unsigned int cpumask_next_andnot(int n, const struct cpumask *srcp1, const struct cpumask *srcp2)
+{
+	/* -1 is a legal arg here. */
+	if (n != -1)
+		cpumask_check(n);
+	return find_next_andnot_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits, n+1);
+}
+
+/**
+ * cpumask_next_nor - return the next cpu from ~(*srcp1 | *srcp2)
+ * @n: the cpu prior to the place to search (ie. return will be > @n)
+ * @src1p: the first input
+ * @src2p: the second input
+ *
+ * Returns >= nr_cpu_ids if no cpus match in both.
+ */
+static __always_inline
+unsigned int cpumask_next_nor(int n, const struct cpumask *srcp1, const struct cpumask *srcp2)
+{
+	/* -1 is a legal arg here. */
+	if (n != -1)
+		cpumask_check(n);
+	return find_next_nor_bit(cpumask_bits(srcp1), cpumask_bits(srcp2), small_cpumask_bits, n+1);
+}
+
 #if NR_CPUS == 1
 /* Uniprocessor: there is only one valid CPU */
 static inline unsigned int cpumask_local_spread(unsigned int i, int node)
-- 
2.39.2