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/char/genrtc.c b/drivers/char/genrtc.c
index b6c2cc167c11..2aa69f97360d 100644
--- a/drivers/char/genrtc.c
+++ b/drivers/char/genrtc.c
@@ -52,7 +52,7 @@
 #include <linux/init.h>
 #include <linux/poll.h>
 #include <linux/proc_fs.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/workqueue.h>
 
 #include <asm/uaccess.h>
@@ -66,6 +66,7 @@
  *      ioctls.
  */
 
+static DEFINE_MUTEX(gen_rtc_mutex);
 static DECLARE_WAIT_QUEUE_HEAD(gen_rtc_wait);
 
 /*
@@ -337,9 +338,9 @@ static long gen_rtc_unlocked_ioctl(struct file *file, unsigned int cmd,
 {
         int ret;
 
-        lock_kernel();
+        mutex_lock(&gen_rtc_mutex);
         ret = gen_rtc_ioctl(file, cmd, arg);
-        unlock_kernel();
+        mutex_unlock(&gen_rtc_mutex);
 
         return ret;
 }
@@ -352,16 +353,16 @@ static long gen_rtc_unlocked_ioctl(struct file *file, unsigned int cmd,
 
 static int gen_rtc_open(struct inode *inode, struct file *file)
 {
-        lock_kernel();
+        mutex_lock(&gen_rtc_mutex);
         if (gen_rtc_status & RTC_IS_OPEN) {
-                unlock_kernel();
+                mutex_unlock(&gen_rtc_mutex);
                 return -EBUSY;
         }
 
         gen_rtc_status |= RTC_IS_OPEN;
         gen_rtc_irq_data = 0;
         irq_active = 0;
-        unlock_kernel();
+        mutex_unlock(&gen_rtc_mutex);
 
         return 0;
 }