[tip:locking/core] cpuset: Make nr_cpusets private

[tip-bot for Paolo Bonzini <tipbot@zytor.com>]

Commit-ID:  be040bea9085a9c2b1700c9e60888777baeb96d5
Gitweb:     http://git.kernel.org/tip/be040bea9085a9c2b1700c9e60888777baeb96d5
Author:     Paolo Bonzini <pbonzini@redhat.com>
AuthorDate: Tue, 1 Aug 2017 17:24:06 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 10 Aug 2017 12:28:57 +0200

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.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Zefan Li <lizefan@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1501601046-35683-4-git-send-email-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 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 898cfe2..e74655d 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -37,12 +37,6 @@ 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_pre_enable_key);
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 8d51516..9ed6a05 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -577,6 +577,13 @@ 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()
  *