[tip:locking/core] locking/lockdep: Make global debug_locks* variables read-mostly

[tip-bot for Waiman Long]

Commit-ID:  01a14bda11add9dcd4a59200f13834d634559935
Gitweb:     https://git.kernel.org/tip/01a14bda11add9dcd4a59200f13834d634559935
Author:     Waiman Long <longman@xxxxxxxxxx>
AuthorDate: Thu, 18 Oct 2018 21:45:18 -0400
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 19 Oct 2018 07:53:18 +0200

locking/lockdep: Make global debug_locks* variables read-mostly

Make the frequently used lockdep global variable debug_locks read-mostly.
As debug_locks_silent is sometime used together with debug_locks,
it is also made read-mostly so that they can be close together.

With false cacheline sharing, cacheline contention problem can happen
depending on what get put into the same cacheline as debug_locks.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Link: http://lkml.kernel.org/r/1539913518-15598-2-git-send-email-longman@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 include/linux/debug_locks.h | 4 ++--
 lib/debug_locks.c           | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/linux/debug_locks.h b/include/linux/debug_locks.h
index 120225e9a366..257ab3c92cb8 100644
--- a/include/linux/debug_locks.h
+++ b/include/linux/debug_locks.h
@@ -8,8 +8,8 @@
 
 struct task_struct;
 
-extern int debug_locks;
-extern int debug_locks_silent;
+extern int debug_locks __read_mostly;
+extern int debug_locks_silent __read_mostly;
 
 
 static inline int __debug_locks_off(void)
diff --git a/lib/debug_locks.c b/lib/debug_locks.c
index 124fdf238b3d..ce51749cc145 100644
--- a/lib/debug_locks.c
+++ b/lib/debug_locks.c
@@ -21,7 +21,7 @@
  * that would just muddy the log. So we report the first one and
  * shut up after that.
  */
-int debug_locks = 1;
+int debug_locks __read_mostly = 1;
 EXPORT_SYMBOL_GPL(debug_locks);
 
 /*
@@ -29,7 +29,7 @@ EXPORT_SYMBOL_GPL(debug_locks);
  * 'silent failure': nothing is printed to the console when
  * a locking bug is detected.
  */
-int debug_locks_silent;
+int debug_locks_silent __read_mostly;
 EXPORT_SYMBOL_GPL(debug_locks_silent);
 
 /*