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/misc/phantom.c b/drivers/misc/phantom.c
index 75ee0d3f6f45..3712e5077e25 100644
--- a/drivers/misc/phantom.c
+++ b/drivers/misc/phantom.c
@@ -24,7 +24,7 @@
 #include <linux/slab.h>
 #include <linux/phantom.h>
 #include <linux/sched.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 
 #include <asm/atomic.h>
 #include <asm/io.h>
@@ -38,6 +38,7 @@
 #define PHB_RUNNING		1
 #define PHB_NOT_OH		2
 
+static DEFINE_MUTEX(phantom_mutex);
 static struct class *phantom_class;
 static int phantom_major;
 
@@ -215,17 +216,17 @@ static int phantom_open(struct inode *inode, struct file *file)
 	struct phantom_device *dev = container_of(inode->i_cdev,
 			struct phantom_device, cdev);
 
-	lock_kernel();
+	mutex_lock(&phantom_mutex);
 	nonseekable_open(inode, file);
 
 	if (mutex_lock_interruptible(&dev->open_lock)) {
-		unlock_kernel();
+		mutex_unlock(&phantom_mutex);
 		return -ERESTARTSYS;
 	}
 
 	if (dev->opened) {
 		mutex_unlock(&dev->open_lock);
-		unlock_kernel();
+		mutex_unlock(&phantom_mutex);
 		return -EINVAL;
 	}
 
@@ -236,7 +237,7 @@ static int phantom_open(struct inode *inode, struct file *file)
 	atomic_set(&dev->counter, 0);
 	dev->opened++;
 	mutex_unlock(&dev->open_lock);
-	unlock_kernel();
+	mutex_unlock(&phantom_mutex);
 	return 0;
 }