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From: Arnd Bergmann on 11 Jul 2010 17:30
All these files use the big kernel lock in a trivial
way to serialize their private file operations,
typically resulting from an earlier semi-automatic
pushdown from VFS.

None of these drivers appears to want to lock against
other code, and they all use the BKL as the top-level
lock in their file operations, meaning that there
is no lock-order inversion problem.

Consequently, we can remove the BKL completely,
replacing it with a per-file mutex in every case.
Using a scripted approach means we can avoid
typos.

file=$1
name=$2
if grep -q lock_kernel ${file} ; then
if grep -q 'include.*linux.mutex.h' ${file} ; then
sed -i '/include.*<linux\/smp_lock.h>/d' ${file}
else
sed -i 's/include.*<linux\/smp_lock.h>.*$/include <linux\/mutex.h>/g' ${file}
fi
sed -i ${file} \
-e "/^#include.*linux.mutex.h/,$ {
1,/^\(static\|int\|long\)/ {
/^\(static\|int\|long\)/istatic DEFINE_MUTEX(${name}_mutex);

} }" \
-e "s/\(un\)*lock_kernel\>[ ]*()/mutex_\1lock(\&${name}_mutex)/g" \
-e '/[ ]*cycle_kernel_lock();/d'
else
sed -i -e '/include.*\<smp_lock.h\>/d' ${file} \
-e '/cycle_kernel_lock()/d'
fi

Signed-off-by: Arnd Bergmann <arnd(a)arndb.de>
Cc: linux-cris-kernel(a)axis.com
Cc: Jesper Nilsson <jesper.nilsson(a)axis.com>
---
arch/cris/arch-v10/drivers/eeprom.c | 2 --
arch/cris/arch-v10/drivers/i2c.c | 2 --
arch/cris/arch-v32/drivers/cryptocop.c | 2 --
arch/cris/arch-v32/drivers/i2c.c | 12 ++++++------
4 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/cris/arch-v10/drivers/eeprom.c b/arch/cris/arch-v10/drivers/eeprom.c
index c340550..5047a33 100644
--- a/arch/cris/arch-v10/drivers/eeprom.c
+++ b/arch/cris/arch-v10/drivers/eeprom.c
@@ -28,7 +28,6 @@
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/interrupt.h>
-#include <linux/smp_lock.h>
#include <linux/wait.h>
#include <asm/uaccess.h>
#include "i2c.h"
@@ -376,7 +375,6 @@ int __init eeprom_init(void)
/* Opens the device. */
static int eeprom_open(struct inode * inode, struct file * file)
{
- cycle_kernel_lock();
if(iminor(inode) != EEPROM_MINOR_NR)
return -ENXIO;
if(imajor(inode) != EEPROM_MAJOR_NR)
diff --git a/arch/cris/arch-v10/drivers/i2c.c b/arch/cris/arch-v10/drivers/i2c.c
index a8737a8..f34fe71 100644
--- a/arch/cris/arch-v10/drivers/i2c.c
+++ b/arch/cris/arch-v10/drivers/i2c.c
@@ -14,7 +14,6 @@

#include <linux/module.h>
#include <linux/sched.h>
-#include <linux/smp_lock.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
@@ -566,7 +565,6 @@ i2c_readreg(unsigned char theSlave, unsigned char theReg)
static int
i2c_open(struct inode *inode, struct file *filp)
{
- cycle_kernel_lock();
return 0;
}

diff --git a/arch/cris/arch-v32/drivers/cryptocop.c b/arch/cris/arch-v32/drivers/cryptocop.c
index b70fb34..9f80da0 100644
--- a/arch/cris/arch-v32/drivers/cryptocop.c
+++ b/arch/cris/arch-v32/drivers/cryptocop.c
@@ -11,7 +11,6 @@
#include <linux/string.h>
#include <linux/fs.h>
#include <linux/mm.h>
-#include <linux/smp_lock.h>
#include <linux/spinlock.h>
#include <linux/stddef.h>

@@ -2307,7 +2306,6 @@ static int cryptocop_open(struct inode *inode, struct file *filp)
{
int p = iminor(inode);

- cycle_kernel_lock();
if (p != CRYPTOCOP_MINOR) return -EINVAL;

filp->private_data = NULL;
diff --git a/arch/cris/arch-v32/drivers/i2c.c b/arch/cris/arch-v32/drivers/i2c.c
index 2fd6a74..5a3e900 100644
--- a/arch/cris/arch-v32/drivers/i2c.c
+++ b/arch/cris/arch-v32/drivers/i2c.c
@@ -32,7 +32,7 @@
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>

#include <asm/etraxi2c.h>

@@ -47,6 +47,7 @@
#define D(x)

#define I2C_MAJOR 123 /* LOCAL/EXPERIMENTAL */
+static DEFINE_MUTEX(i2c_mutex);
static const char i2c_name[] = "i2c";

#define CLOCK_LOW_TIME 8
@@ -636,7 +637,6 @@ i2c_readreg(unsigned char theSlave, unsigned char theReg)
static int
i2c_open(struct inode *inode, struct file *filp)
{
- cycle_kernel_lock();
return 0;
}

@@ -665,11 +665,11 @@ i2c_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
I2C_ARGREG(arg),
I2C_ARGVALUE(arg)));

- lock_kernel();
+ mutex_lock(&i2c_mutex);
ret = i2c_writereg(I2C_ARGSLAVE(arg),
I2C_ARGREG(arg),
I2C_ARGVALUE(arg));
- unlock_kernel();
+ mutex_unlock(&i2c_mutex);
return ret;

case I2C_READREG:
@@ -679,9 +679,9 @@ i2c_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
D(printk("i2cr %d %d ",
I2C_ARGSLAVE(arg),
I2C_ARGREG(arg)));
- lock_kernel();
+ mutex_lock(&i2c_mutex);
val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg));
- unlock_kernel();
+ mutex_unlock(&i2c_mutex);
D(printk("= %d\n", val));
return val;
}
--
1.7.1

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Next: [PATCH 06/12] net: autoconvert trivial BKL users to private mutex