sbus: 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.

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/sbus/char/uctrl.c b/drivers/sbus/char/uctrl.c
index 5f253665a1d..079da4cb45a 100644
--- a/drivers/sbus/char/uctrl.c
+++ b/drivers/sbus/char/uctrl.c
@@ -9,7 +9,7 @@
 #include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/ioport.h>
 #include <linux/init.h>
 #include <linux/miscdevice.h>
@@ -72,6 +72,7 @@ struct ts102_regs {
 #define UCTRL_STAT_RXNE_STA        0x04    /* receive FIFO not empty status */
 #define UCTRL_STAT_RXO_STA         0x08    /* receive FIFO overflow status */
 
+static DEFINE_MUTEX(uctrl_mutex);
 static const char *uctrl_extstatus[16] = {
         "main power available",
         "internal battery attached",
@@ -210,10 +211,10 @@ uctrl_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 static int
 uctrl_open(struct inode *inode, struct file *file)
 {
-	lock_kernel();
+	mutex_lock(&uctrl_mutex);
 	uctrl_get_event_status(global_driver);
 	uctrl_get_external_status(global_driver);
-	unlock_kernel();
+	mutex_unlock(&uctrl_mutex);
 	return 0;
 }