linux-kernel - [PATCH] kernel/notifier: Use BUG_ON instead of if condition followed by BUG

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Message-Id: <1619164597-69309-1-git-send-email-zhouchuangao@vivo.com>
Date:   Fri, 23 Apr 2021 00:56:34 -0700
From:   zhouchuangao <zhouchuangao@...o.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Joerg Roedel <jroedel@...e.de>, Ingo Molnar <mingo@...nel.org>,
        zhouchuangao <zhouchuangao@...o.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kernel/notifier: Use BUG_ON instead of if condition followed by BUG

BUG_ON uses unlikely in if(). Through disassembly, we can see that
brk #0x800 is compiled to the end of the function.
As you can see below:
    ......
    ffffff8008660bec:   d65f03c0    ret
    ffffff8008660bf0:   d4210000    brk #0x800

Usually, the condition in if () is not satisfied. For the
multi-stage pipeline, we do not need to perform fetch decode
and excute operation on brk instruction.

In my opinion, this can improve the efficiency of the
multi-stage pipeline.

Signed-off-by: zhouchuangao <zhouchuangao@...o.com>
---
 kernel/notifier.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/notifier.c b/kernel/notifier.c
index 1b019cb..2b0ed7d 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -522,8 +522,7 @@ EXPORT_SYMBOL_GPL(srcu_notifier_call_chain);
 void srcu_init_notifier_head(struct srcu_notifier_head *nh)
 {
 	mutex_init(&nh->mutex);
-	if (init_srcu_struct(&nh->srcu) < 0)
-		BUG();
+	BUG_ON(init_srcu_struct(&nh->srcu) < 0);
 	nh->head = NULL;
 }
 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
-- 
2.7.4