linux-kernel - [RFC PATCH 1/2] cpumask: Implement cpumask_next

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Message-Id: <20240903190650.53644-2-mathieu.desnoyers@efficios.com>
Date: Tue,  3 Sep 2024 15:06:49 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Cc: linux-kernel@...r.kernel.org,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Valentin Schneider <vschneid@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ben Segall <bsegall@...gle.com>,
	Yury Norov <yury.norov@...il.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: [RFC PATCH 1/2] cpumask: Implement cpumask_next_andnot

Allow finding the next bit within two input cpumasks which is
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>
---
 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