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From: Daniel Jordan <daniel.m.jordan@oracle.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sasha Levin <sashal@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>,
	Herbert Xu <herbert@gondor.apana.org.au>,
	Mathias Krause <minipli@googlemail.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	stable@vger.kernel.org, linux-crypto@vger.kernel.org,
	Daniel Jordan <daniel.m.jordan@oracle.com>
Subject: [stable-4.4 2/5] sched/fair, cpumask: Export for_each_cpu_wrap()
Date: Thu, 21 May 2020 16:51:42 -0400
Message-ID: <20200521205145.1953392-2-daniel.m.jordan@oracle.com> (raw)
In-Reply-To: <20200521205145.1953392-1-daniel.m.jordan@oracle.com>

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit c743f0a5c50f2fcbc628526279cfa24f3dabe182 ]

More users for for_each_cpu_wrap() have appeared. Promote the construct
to generic cpumask interface.

The implementation is slightly modified to reduce arguments.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Lauro Ramos Venancio <lvenanci@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: lwang@redhat.com
Link: http://lkml.kernel.org/r/20170414122005.o35me2h5nowqkxbv@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[dj: include only what's added to the cpumask interface, 4.4 doesn't
     have them in the scheduler]
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
---
 include/linux/cpumask.h | 17 +++++++++++++++++
 lib/cpumask.c           | 32 ++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index bb3a4bb35183..1322883e7b46 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -232,6 +232,23 @@ unsigned int cpumask_local_spread(unsigned int i, int node);
 		(cpu) = cpumask_next_zero((cpu), (mask)),	\
 		(cpu) < nr_cpu_ids;)
 
+extern int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap);
+
+/**
+ * for_each_cpu_wrap - iterate over every cpu in a mask, starting at a specified location
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask: the cpumask poiter
+ * @start: the start location
+ *
+ * The implementation does not assume any bit in @mask is set (including @start).
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_wrap(cpu, mask, start)					\
+	for ((cpu) = cpumask_next_wrap((start)-1, (mask), (start), false);	\
+	     (cpu) < nr_cpumask_bits;						\
+	     (cpu) = cpumask_next_wrap((cpu), (mask), (start), true))
+
 /**
  * for_each_cpu_and - iterate over every cpu in both masks
  * @cpu: the (optionally unsigned) integer iterator
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 5a70f6196f57..24f06e7abf92 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -42,6 +42,38 @@ int cpumask_any_but(const struct cpumask *mask, unsigned int cpu)
 	return i;
 }
 
+/**
+ * cpumask_next_wrap - helper to implement for_each_cpu_wrap
+ * @n: the cpu prior to the place to search
+ * @mask: the cpumask pointer
+ * @start: the start point of the iteration
+ * @wrap: assume @n crossing @start terminates the iteration
+ *
+ * Returns >= nr_cpu_ids on completion
+ *
+ * Note: the @wrap argument is required for the start condition when
+ * we cannot assume @start is set in @mask.
+ */
+int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
+{
+	int next;
+
+again:
+	next = cpumask_next(n, mask);
+
+	if (wrap && n < start && next >= start) {
+		return nr_cpumask_bits;
+
+	} else if (next >= nr_cpumask_bits) {
+		wrap = true;
+		n = -1;
+		goto again;
+	}
+
+	return next;
+}
+EXPORT_SYMBOL(cpumask_next_wrap);
+
 /* These are not inline because of header tangles. */
 #ifdef CONFIG_CPUMASK_OFFSTACK
 /**
-- 
2.26.2


  reply index

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-21 20:51 [stable-4.4 1/5] padata: set cpu_index of unused CPUs to -1 Daniel Jordan
2020-05-21 20:51 ` Daniel Jordan [this message]
2020-05-21 20:51 ` [stable-4.4 3/5] padata: Replace delayed timer with immediate workqueue in padata_reorder Daniel Jordan
2020-05-21 20:51 ` [stable-4.4 4/5] padata: initialize pd->cpu with effective cpumask Daniel Jordan
2020-05-21 20:51 ` [stable-4.4 5/5] padata: purge get_cpu and reorder_via_wq from padata_do_serial Daniel Jordan
2020-05-22  0:20 ` [stable-4.4 1/5] padata: set cpu_index of unused CPUs to -1 Ben Hutchings

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