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, 6 insertions, 5 deletions

diff --git a/drivers/char/nvram.c b/drivers/char/nvram.c
index 66d2917b003f..166f1e7aaa7e 100644
--- a/drivers/char/nvram.c
+++ b/drivers/char/nvram.c
@@ -109,10 +109,11 @@
 #include <linux/spinlock.h>
 #include <linux/io.h>
 #include <linux/uaccess.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 
 #include <asm/system.h>
 
+static DEFINE_MUTEX(nvram_mutex);
 static DEFINE_SPINLOCK(nvram_state_lock);
 static int nvram_open_cnt;	/* #times opened */
 static int nvram_open_mode;	/* special open modes */
@@ -308,7 +309,7 @@ static long nvram_ioctl(struct file *file, unsigned int cmd,
 		if (!capable(CAP_SYS_ADMIN))
 			return -EACCES;
 
-		lock_kernel();
+		mutex_lock(&nvram_mutex);
 		spin_lock_irq(&rtc_lock);
 
 		for (i = 0; i < NVRAM_BYTES; ++i)
@@ -316,7 +317,7 @@ static long nvram_ioctl(struct file *file, unsigned int cmd,
 		__nvram_set_checksum();
 
 		spin_unlock_irq(&rtc_lock);
-		unlock_kernel();
+		mutex_unlock(&nvram_mutex);
 		return 0;
 
 	case NVRAM_SETCKS:
@@ -325,11 +326,11 @@ static long nvram_ioctl(struct file *file, unsigned int cmd,
 		if (!capable(CAP_SYS_ADMIN))
 			return -EACCES;
 
-		lock_kernel();
+		mutex_lock(&nvram_mutex);
 		spin_lock_irq(&rtc_lock);
 		__nvram_set_checksum();
 		spin_unlock_irq(&rtc_lock);
-		unlock_kernel();
+		mutex_unlock(&nvram_mutex);
 		return 0;
 
 	default: