From 6e8c1ccbe24d4adf3b4648324fdf5c401dcff5e7 Mon Sep 17 00:00:00 2001
From: Mateusz Guzik <mjg@FreeBSD.org>
Date: Fri, 7 Dec 2018 12:06:03 +0000
Subject: [PATCH] Annotate Giant drop/pickup macros with __predict_false

They are used in important places of the kernel with the lock not being held
majority of the time.

Sponsored by:	The FreeBSD Foundation
---
 sys/kern/kern_lock.c | 4 ++--
 sys/sys/mutex.h      | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 65a52340e59..d844cfc47cc 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -96,14 +96,14 @@ CTASSERT(LK_UNLOCKED == (LK_UNLOCKED &
 	int _i = 0;							\
 	WITNESS_SAVE_DECL(Giant)
 #define	GIANT_RESTORE() do {						\
-	if (_i > 0) {							\
+	if (__predict_false(_i > 0)) {					\
 		while (_i--)						\
 			mtx_lock(&Giant);				\
 		WITNESS_RESTORE(&Giant.lock_object, Giant);		\
 	}								\
 } while (0)
 #define	GIANT_SAVE() do {						\
-	if (mtx_owned(&Giant)) {					\
+	if (__predict_false(mtx_owned(&Giant))) {			\
 		WITNESS_SAVE(&Giant.lock_object, Giant);		\
 		while (mtx_owned(&Giant)) {				\
 			_i++;						\
diff --git a/sys/sys/mutex.h b/sys/sys/mutex.h
index d4c9d1cbc81..caacf2ef427 100644
--- a/sys/sys/mutex.h
+++ b/sys/sys/mutex.h
@@ -496,7 +496,7 @@ do {									\
 	int _giantcnt = 0;						\
 	WITNESS_SAVE_DECL(Giant);					\
 									\
-	if (mtx_owned(&Giant)) {					\
+	if (__predict_false(mtx_owned(&Giant))) {			\
 		WITNESS_SAVE(&Giant.lock_object, Giant);		\
 		for (_giantcnt = 0; mtx_owned(&Giant) &&		\
 		    !SCHEDULER_STOPPED(); _giantcnt++)			\
@@ -509,7 +509,7 @@ do {									\
 
 #define PARTIAL_PICKUP_GIANT()						\
 	mtx_assert(&Giant, MA_NOTOWNED);				\
-	if (_giantcnt > 0) {						\
+	if (__predict_false(_giantcnt > 0)) {				\
 		while (_giantcnt--)					\
 			mtx_lock(&Giant);				\
 		WITNESS_RESTORE(&Giant.lock_object, Giant);		\