[RFC PATCH 1/2] cpumask: Implement cpumask_next_andnot

[Mathieu Desnoyers]

Allow finding the next bit within two input cpumasks which is
respectively one and zero.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Yury Norov <yury.norov@xxxxxxxxx>
Cc: Rasmus Villemoes <linux@xxxxxxxxxxxxxxxxxx>
---
 include/linux/cpumask.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 23686bed441d..5da1c66cfa65 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -246,6 +246,23 @@ 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);
+}
+
 #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