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, 8 insertions, 7 deletions

diff --git a/drivers/watchdog/cpwd.c b/drivers/watchdog/cpwd.c
index 566343b..b7d96e6 100644
--- a/drivers/watchdog/cpwd.c
+++ b/drivers/watchdog/cpwd.c
@@ -25,7 +25,7 @@
 #include <linux/ioport.h>
 #include <linux/timer.h>
 #include <linux/slab.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
@@ -89,6 +89,7 @@ struct cpwd {
 	} devs[WD_NUMDEVS];
 };
 
+static DEFINE_MUTEX(cpwd_mutex);
 static struct cpwd *cpwd_device;
 
 /* Sun uses Altera PLD EPF8820ATC144-4
@@ -368,7 +369,7 @@ static int cpwd_open(struct inode *inode, struct file *f)
 {
 	struct cpwd *p = cpwd_device;
 
-	lock_kernel();
+	mutex_lock(&cpwd_mutex);
 	switch (iminor(inode)) {
 	case WD0_MINOR:
 	case WD1_MINOR:
@@ -376,7 +377,7 @@ static int cpwd_open(struct inode *inode, struct file *f)
 		break;
 
 	default:
-		unlock_kernel();
+		mutex_unlock(&cpwd_mutex);
 		return -ENODEV;
 	}
 
@@ -386,13 +387,13 @@ static int cpwd_open(struct inode *inode, struct file *f)
 				IRQF_SHARED, DRIVER_NAME, p)) {
 			printk(KERN_ERR PFX "Cannot register IRQ %d\n",
 				p->irq);
-			unlock_kernel();
+			mutex_unlock(&cpwd_mutex);
 			return -EBUSY;
 		}
 		p->initialized = true;
 	}
 
-	unlock_kernel();
+	mutex_unlock(&cpwd_mutex);
 
 	return nonseekable_open(inode, f);
 }
@@ -482,9 +483,9 @@ static long cpwd_compat_ioctl(struct file *file, unsigned int cmd,
 	case WIOCSTART:
 	case WIOCSTOP:
 	case WIOCGSTAT:
-		lock_kernel();
+		mutex_lock(&cpwd_mutex);
 		rval = cpwd_ioctl(file, cmd, arg);
-		unlock_kernel();
+		mutex_unlock(&cpwd_mutex);
 		break;
 
 	/* everything else is handled by the generic compat layer */