[PATCH] fix race and remove BKL from wdt977

We've seen this in several other drivers, most recently the indydog one.
  If two simultaneous opens occur, they race, they device gets opened
twice, blah, blah, blah.  Using atomic bitops fixes this.  The BKL is
not needed.

drivers/char/wdt977.c

@@ -90,7 +90,7 @@ int kick_wdog(void)
 static int wdt977_open(struct inode *inode, struct file *file)
 {
 
-	if(timer_alive)
+	if( test_and_set_bit(0,&timer_alive) )
 		return -EBUSY;
 
 	/* convert seconds to minutes, rounding up */
@@ -104,7 +104,6 @@ static int wdt977_open(struct inode *inode, struct file *file)
 		/* do not permit disabling the watchdog by writing 0 to reg. 0xF2 */
 		if (!timeoutM) timeoutM = DEFAULT_TIMEOUT;
 	}
-	timer_alive++;
 
 	if (machine_is_netwinder())
 	{
@@ -165,8 +164,6 @@ static int wdt977_release(struct inode *inode, struct file *file)
 	 */
 	if (!nowayout)
 	{
-		lock_kernel();
-
 		/* unlock the SuperIO chip */
 		outb(0x87,0x370);
 		outb(0x87,0x370);
@@ -196,8 +193,7 @@ static int wdt977_release(struct inode *inode, struct file *file)
 		/* lock the SuperIO chip */
 		outb(0xAA,0x370);
 
-		timer_alive=0;
-		unlock_kernel();
+		clear_bit(0,&timer_alive);
 
 		printk(KERN_INFO "Wdt977 Watchdog: shutdown\n");
 	}