monreader: BKL pushdown

[jmc: added <linux/smp_lock.h>]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

drivers/s390/char/monreader.c

@@ -11,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/init.h>
+#include <linux/smp_lock.h>
 #include <linux/errno.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
@@ -340,6 +341,7 @@ static int mon_open(struct inode *inode, struct file *filp)
 	/*
 	 * only one user allowed
 	 */
+	lock_kernel();
 	rc = -EBUSY;
 	if (test_and_set_bit(MON_IN_USE, &mon_in_use))
 		goto out;
@@ -377,6 +379,7 @@ static int mon_open(struct inode *inode, struct file *filp)
 	}
 	P_INFO("open, established connection to *MONITOR service\n\n");
 	filp->private_data = monpriv;
+	unlock_kernel();
 	return nonseekable_open(inode, filp);
 
 out_path:
@@ -386,6 +389,7 @@ static int mon_open(struct inode *inode, struct file *filp)
 out_use:
 	clear_bit(MON_IN_USE, &mon_in_use);
 out:
+	unlock_kernel();
 	return rc;
 }