tlckl: BKL pushdown

Put explicit lock_kernel calls into tlclk_open()
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

drivers/char/tlclk.c

@@ -36,6 +36,7 @@
 #include <linux/ioport.h>
 #include <linux/interrupt.h>
 #include <linux/spinlock.h>
+#include <linux/smp_lock.h>
 #include <linux/timer.h>
 #include <linux/sysfs.h>
 #include <linux/device.h>
@@ -204,11 +205,14 @@ static int tlclk_open(struct inode *inode, struct file *filp)
 {
 	int result;
 
-	if (test_and_set_bit(0, &useflags))
-		return -EBUSY;
+	lock_kernel();
+	if (test_and_set_bit(0, &useflags)) {
+		result = -EBUSY;
 		/* this legacy device is always one per system and it doesn't
 		 * know how to handle multiple concurrent clients.
 		 */
+		goto out;
+	}
 
 	/* Make sure there is no interrupt pending while
 	 * initialising interrupt handler */
@@ -218,13 +222,14 @@ static int tlclk_open(struct inode *inode, struct file *filp)
 	 * we can't share this IRQ */
 	result = request_irq(telclk_interrupt, &tlclk_interrupt,
 			     IRQF_DISABLED, "telco_clock", tlclk_interrupt);
-	if (result == -EBUSY) {
+	if (result == -EBUSY)
 		printk(KERN_ERR "tlclk: Interrupt can't be reserved.\n");
-		return -EBUSY;
-	}
-	inb(TLCLK_REG6);	/* Clear interrupt events */
+	else
+		inb(TLCLK_REG6);	/* Clear interrupt events */
 
-	return 0;
+out:
+	unlock_kernel();
+	return result;
 }
 
 static int tlclk_release(struct inode *inode, struct file *filp)