From 88e77dc6a354095ddaaae715bc0d3b55702fa3db Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 20 Feb 2018 16:01:36 +0100
Subject: [PATCH] locking/mutex: Add comment to __mutex_owner() to deter usage

Attempt to deter usage, this is not a public interface. It is entirely
possible to implement a conformant mutex without having this owner
field (in fact, we used to have that).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/mutex.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index f25c13423bd4..cb3bbed4e633 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -66,6 +66,11 @@ struct mutex {
 #endif
 };
 
+/*
+ * Internal helper function; C doesn't allow us to hide it :/
+ *
+ * DO NOT USE (outside of mutex code).
+ */
 static inline struct task_struct *__mutex_owner(struct mutex *lock)
 {
 	return (struct task_struct *)(atomic_long_read(&lock->owner) & ~0x07);