linux-kernel - [PATCH] driver core: Add branch prediction hints in really

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Message-Id: <20181106134630.29591-1-smuchun@gmail.com>
Date:   Tue,  6 Nov 2018 21:46:30 +0800
From:   Muchun Song <smuchun@...il.com>
To:     gregkh@...uxfoundation.org, rafael@...nel.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH] driver core: Add branch prediction hints in really_probe()

If condition is false in most cases. So, add an unlikely() to the if
condition, so that the optimizer assumes that the condition is false.

Signed-off-by: Muchun Song <smuchun@...il.com>
---
 drivers/base/dd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 169412ee4ae8..8eba453c4e5d 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -450,7 +450,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 	bool test_remove = IS_ENABLED(CONFIG_DEBUG_TEST_DRIVER_REMOVE) &&
 			   !drv->suppress_bind_attrs;
 
-	if (defer_all_probes) {
+	if (unlikely(defer_all_probes)) {
 		/*
 		 * Value of defer_all_probes can be set only by
 		 * device_defer_all_probes_enable() which, in turn, will call
@@ -508,7 +508,7 @@ static int really_probe(struct device *dev, struct device_driver *drv)
 			goto probe_failed;
 	}
 
-	if (test_remove) {
+	if (unlikely(test_remove)) {
 		test_remove = false;
 
 		if (dev->bus->remove)
-- 
2.17.1