From 43759fe5a137389e94ed6d4680c3c63c17273158 Mon Sep 17 00:00:00 2001
From: Frederic Weisbecker <frederic@kernel.org>
Date: Wed, 11 Nov 2020 23:53:13 +0100
Subject: [PATCH] cpu/hotplug: Add lockdep_is_cpus_held()

This commit adds a lockdep_is_cpus_held() function to verify that the
proper locks are held and that various operations are running in the
correct context.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 include/linux/cpu.h | 2 ++
 kernel/cpu.c        | 7 +++++++
 2 files changed, 9 insertions(+)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index d6428aaf67e7..3aaa0687e8df 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -111,6 +111,8 @@ static inline void cpu_maps_update_done(void)
 #endif /* CONFIG_SMP */
 extern struct bus_type cpu_subsys;
 
+extern int lockdep_is_cpus_held(void);
+
 #ifdef CONFIG_HOTPLUG_CPU
 extern void cpus_write_lock(void);
 extern void cpus_write_unlock(void);
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 4e11e91010e1..1b6302ecbabe 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -330,6 +330,13 @@ void lockdep_assert_cpus_held(void)
 	percpu_rwsem_assert_held(&cpu_hotplug_lock);
 }
 
+#ifdef CONFIG_LOCKDEP
+int lockdep_is_cpus_held(void)
+{
+	return percpu_rwsem_is_held(&cpu_hotplug_lock);
+}
+#endif
+
 static void lockdep_acquire_cpus_lock(void)
 {
 	rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);