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

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Date:   Sat, 17 Apr 2021 03:22:01 -0700
From:   zhouchuangao <zhouchuangao@...o.com>
To:     Jessica Yu <jeyu@...nel.org>, linux-kernel@...r.kernel.org
Cc:     zhouchuangao <zhouchuangao@...o.com>
Subject: [PATCH] kernel/module: Use BUG_ON instead of if condition followed by BUG.

First:
This patch comes from cocinelle warning.

Second:
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/module.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 3047935..f46fc4f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1014,8 +1014,8 @@ void __symbol_put(const char *symbol)
 	};

 	preempt_disable();
-	if (!find_symbol(&fsa))
-		BUG();
+	BUG_ON(!find_symbol(&fsa));
+
 	module_put(fsa.owner);
 	preempt_enable();
 }
-- 
2.7.4