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, 3 insertions, 3 deletions

diff --git a/drivers/char/xilinx_hwicap/xilinx_hwicap.c b/drivers/char/xilinx_hwicap/xilinx_hwicap.c
index b663d57..d985204 100644
--- a/drivers/char/xilinx_hwicap/xilinx_hwicap.c
+++ b/drivers/char/xilinx_hwicap/xilinx_hwicap.c
@@ -81,7 +81,6 @@
 #include <linux/poll.h>
 #include <linux/proc_fs.h>
 #include <linux/mutex.h>
-#include <linux/smp_lock.h>
 #include <linux/sysctl.h>
 #include <linux/fs.h>
 #include <linux/cdev.h>
@@ -112,6 +111,7 @@
 #define HWICAP_DEVICES 1
 
 /* An array, which is set to true when the device is registered. */
+static DEFINE_MUTEX(hwicap_mutex);
 static bool probed_devices[HWICAP_DEVICES];
 static struct mutex icap_sem;
 
@@ -502,7 +502,7 @@ static int hwicap_open(struct inode *inode, struct file *file)
 	struct hwicap_drvdata *drvdata;
 	int status;
 
-	lock_kernel();
+	mutex_lock(&hwicap_mutex);
 	drvdata = container_of(inode->i_cdev, struct hwicap_drvdata, cdev);
 
 	status = mutex_lock_interruptible(&drvdata->sem);
@@ -528,7 +528,7 @@ static int hwicap_open(struct inode *inode, struct file *file)
  error:
 	mutex_unlock(&drvdata->sem);
  out:
-	unlock_kernel();
+	mutex_unlock(&hwicap_mutex);
 	return status;
 }