Add a bunch of cycle_kernel_lock() calls

All of the open() functions which don't need the BKL on their face may
still depend on its acquisition to serialize opens against driver
initialization.  So make those functions acquire then release the BKL to be
on the safe side.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

drivers/char/dtlk.c

@@ -56,6 +56,7 @@
 #include <linux/errno.h>	/* for -EBUSY */
 #include <linux/ioport.h>	/* for request_region */
 #include <linux/delay.h>	/* for loops_per_jiffy */
+#include <linux/smp_lock.h>	/* cycle_kernel_lock() */
 #include <asm/io.h>		/* for inb_p, outb_p, inb, outb, etc. */
 #include <asm/uaccess.h>	/* for get_user, etc. */
 #include <linux/wait.h>		/* for wait_queue */
@@ -288,12 +289,12 @@ static int dtlk_ioctl(struct inode *inode,
 	}
 }
 
-/* No BKL needed here; "dtlk_busy" is the only global resource,
-   and it is not ever set by anybody (test is broken) */
+/* Note that nobody ever sets dtlk_busy... */
 static int dtlk_open(struct inode *inode, struct file *file)
 {
 	TRACE_TEXT("(dtlk_open");
 
+	cycle_kernel_lock();
 	nonseekable_open(inode, file);
 	switch (iminor(inode)) {
 	case DTLK_MINOR: