drivers: autoconvert trivial BKL users to private mutex

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.

These drivers do not seem to be under active
maintainance from my brief investigation. Apologies
to those maintainers that I have missed.

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@arndb.de>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/rtc/rtc-m41t80.c b/drivers/rtc/rtc-m41t80.c
index d60557c..512dca1 100644
--- a/drivers/rtc/rtc-m41t80.c
+++ b/drivers/rtc/rtc-m41t80.c
@@ -20,7 +20,7 @@
 #include <linux/module.h>
 #include <linux/rtc.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/string.h>
 #ifdef CONFIG_RTC_DRV_M41T80_WDT
 #include <linux/fs.h>
@@ -68,6 +68,7 @@
 
 #define DRV_VERSION "0.05"
 
+static DEFINE_MUTEX(m41t80_rtc_mutex);
 static const struct i2c_device_id m41t80_id[] = {
 	{ "m41t62", M41T80_FEATURE_SQ | M41T80_FEATURE_SQ_ALT },
 	{ "m41t65", M41T80_FEATURE_HT | M41T80_FEATURE_WD },
@@ -677,9 +678,9 @@ static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
 {
 	int ret;
 
-	lock_kernel();
+	mutex_lock(&m41t80_rtc_mutex);
 	ret = wdt_ioctl(file, cmd, arg);
-	unlock_kernel();
+	mutex_unlock(&m41t80_rtc_mutex);
 
 	return ret;
 }
@@ -693,16 +694,16 @@ static long wdt_unlocked_ioctl(struct file *file, unsigned int cmd,
 static int wdt_open(struct inode *inode, struct file *file)
 {
 	if (MINOR(inode->i_rdev) == WATCHDOG_MINOR) {
-		lock_kernel();
+		mutex_lock(&m41t80_rtc_mutex);
 		if (test_and_set_bit(0, &wdt_is_open)) {
-			unlock_kernel();
+			mutex_unlock(&m41t80_rtc_mutex);
 			return -EBUSY;
 		}
 		/*
 		 *	Activate
 		 */
 		wdt_is_open = 1;
-		unlock_kernel();
+		mutex_unlock(&m41t80_rtc_mutex);
 		return nonseekable_open(inode, file);
 	}
 	return -ENODEV;