linux-kernel - [PATCH RFC] BKL not necessary in cpuid

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Date:	Wed, 7 Oct 2009 20:19:32 +0200 (CEST)
From:	John Kacur <jkacur@...hat.com>
To:	tglx@...utronix.de, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
cc:	linux-rt-users@...r.kernel.org,
	Clark Williams <williams@...hat.com>
Subject: [PATCH RFC] BKL not necessary in cpuid_open


I've been staring at the BKL lock in cpuid_open, and I can't see what it 
is protecting. However, I may have missed something - even something 
obvious, so comments are welcome.

>From 25c0f07b3ec5533c0e690e06198baa4300ee4a8c Mon Sep 17 00:00:00 2001
From: John Kacur <jkacur@...hat.com>
Date: Wed, 7 Oct 2009 20:06:12 +0200
Subject: [PATCH] The BKL is not necessary in cpuid_open
 Most of the variables are local to the function. It IS possible that for
 struct cpuinfo_x86 *c
 c could point to the same area. However, this is used read only.

Signed-off-by: John Kacur <jkacur@...hat.com>
---
 arch/x86/kernel/cpuid.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 6a52d4b..8bb8401 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -118,8 +118,6 @@ static int cpuid_open(struct inode *inode, struct file *file)
 	struct cpuinfo_x86 *c;
 	int ret = 0;
 
-	lock_kernel();
-
 	cpu = iminor(file->f_path.dentry->d_inode);
 	if (cpu >= nr_cpu_ids || !cpu_online(cpu)) {
 		ret = -ENXIO;	/* No such CPU */
@@ -129,7 +127,6 @@ static int cpuid_open(struct inode *inode, struct file *file)
 	if (c->cpuid_level < 0)
 		ret = -EIO;	/* CPUID not supported */
 out:
-	unlock_kernel();
 	return ret;
 }
 
-- 
1.6.0.6

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