linux-kernel - [PATCH 3/3] cpuset: make nr

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Date:   Tue,  1 Aug 2017 17:24:06 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Zefan Li <lizefan@...wei.com>
Subject: [PATCH 3/3] cpuset: make nr_cpusets private

Any use of key->enabled (that is static_key_enabled and static_key_count)
outside jump_label_lock should handle its own serialization.  In the case
of cpusets_enabled_key, the key is always incremented/decremented under
cpuset_mutex, and hence the same rule applies to nr_cpusets.  The rule
*is* respected currently, but the mutex is static so nr_cpusets should
be static too.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Zefan Li <lizefan@...wei.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 include/linux/cpuset.h | 6 ------
 kernel/cgroup/cpuset.c | 7 +++++++
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 119a3f9604b0..cedcc910b7a7 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -24,12 +24,6 @@ static inline bool cpusets_enabled(void)
 	return static_branch_unlikely(&cpusets_enabled_key);
 }
 
-static inline int nr_cpusets(void)
-{
-	/* jump label reference count + the top-level cpuset */
-	return static_key_count(&cpusets_enabled_key.key) + 1;
-}
-
 static inline void cpuset_inc(void)
 {
 	static_branch_inc(&cpusets_enabled_key);
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index ae643412948a..f65db17e9e23 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -576,6 +576,13 @@ static void update_domain_attr_tree(struct sched_domain_attr *dattr,
 	rcu_read_unlock();
 }
 
+/* Must be called with cpuset_mutex held.  */
+static inline int nr_cpusets(void)
+{
+	/* jump label reference count + the top-level cpuset */
+	return static_key_count(&cpusets_enabled_key.key) + 1;
+}
+
 /*
  * generate_sched_domains()
  *
-- 
1.8.3.1