x86-mce: BKL pushdown

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/x86/kernel/cpu/mcheck/mce_64.c

@@ -9,6 +9,7 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/sched.h>
+#include <linux/smp_lock.h>
 #include <linux/string.h>
 #include <linux/rcupdate.h>
 #include <linux/kallsyms.h>
@@ -527,10 +528,12 @@ static int open_exclu;	/* already open exclusive? */
 
 static int mce_open(struct inode *inode, struct file *file)
 {
+	lock_kernel();
 	spin_lock(&mce_state_lock);
 
 	if (open_exclu || (open_count && (file->f_flags & O_EXCL))) {
 		spin_unlock(&mce_state_lock);
+		unlock_kernel();
 		return -EBUSY;
 	}
 
@@ -539,6 +542,7 @@ static int mce_open(struct inode *inode, struct file *file)
 	open_count++;
 
 	spin_unlock(&mce_state_lock);
+	unlock_kernel();
 
 	return nonseekable_open(inode, file);
 }