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, 4 insertions, 3 deletions

diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
index ea7c99f..fe46978 100644
--- a/drivers/char/mmtimer.c
+++ b/drivers/char/mmtimer.c
@@ -32,7 +32,7 @@
 #include <linux/interrupt.h>
 #include <linux/time.h>
 #include <linux/math64.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/slab.h>
 
 #include <asm/uaccess.h>
@@ -59,6 +59,7 @@ extern unsigned long sn_rtc_cycles_per_second;
 
 #define rtc_time()              (*RTC_COUNTER_ADDR)
 
+static DEFINE_MUTEX(mmtimer_mutex);
 static long mmtimer_ioctl(struct file *file, unsigned int cmd,
 						unsigned long arg);
 static int mmtimer_mmap(struct file *file, struct vm_area_struct *vma);
@@ -371,7 +372,7 @@ static long mmtimer_ioctl(struct file *file, unsigned int cmd,
 {
 	int ret = 0;
 
-	lock_kernel();
+	mutex_lock(&mmtimer_mutex);
 
 	switch (cmd) {
 	case MMTIMER_GETOFFSET:	/* offset of the counter */
@@ -414,7 +415,7 @@ static long mmtimer_ioctl(struct file *file, unsigned int cmd,
 		ret = -ENOTTY;
 		break;
 	}
-	unlock_kernel();
+	mutex_unlock(&mmtimer_mutex);
 	return ret;
 }