for_each_cpu_and() is very convenient as it saves having to allocate a
temporary cpumask to store the result of cpumask_and(). The same issue
applies to cpumask_andnot() which doesn't actually need temporary storage
for iteration purposes.
Following what has been done for for_each_cpu_and(), introduce
for_each_cpu_andnot().
Signed-off-by: Valentin Schneider <vschneid@xxxxxxxxxx>
---
include/linux/cpumask.h | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 0d435d0edbcb..295b137717bb 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -237,6 +237,25 @@ unsigned int cpumask_next_and(int n, const struct cpumask *src1p,
nr_cpumask_bits, n + 1);
}
+/**
+ * cpumask_next_andnot - get the next cpu in *src1p & ~*src2p
+ * @n: the cpu prior to the place to search (ie. return will be > @n)
+ * @src1p: the first cpumask pointer
+ * @src2p: the second cpumask pointer
+ *
+ * Returns >= nr_cpu_ids if no further cpus set in *src1p & ~*src2p
+ */
+static 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),
+ nr_cpumask_bits, n + 1);
+}
+
/**
* for_each_cpu - iterate over every cpu in a mask
* @cpu: the (optionally unsigned) integer iterator
@@ -297,6 +316,25 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
(cpu) = cpumask_next_and((cpu), (mask1), (mask2)), \
(cpu) < nr_cpu_ids;)
+/**
+ * for_each_cpu_andnot - iterate over every cpu in one mask but not in the other
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask1: the first cpumask pointer
+ * @mask2: the second cpumask pointer
+ *
+ * This saves a temporary CPU mask in many places. It is equivalent to:
+ * struct cpumask tmp;
+ * cpumask_andnot(&tmp, &mask1, &mask2);
+ * for_each_cpu(cpu, &tmp)
+ * ...
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_andnot(cpu, mask1, mask2) \
+ for ((cpu) = -1; \
+ (cpu) = cpumask_next_andnot((cpu), (mask1), (mask2)), \
+ (cpu) < nr_cpu_ids;)
+
/**
* cpumask_any_but - return a "random" in a cpumask, but not this one.
* @mask: the cpumask to search
--
2.31.1
