diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index bf9290e29013..82222366477f 100644
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -204,6 +204,7 @@
 #include <linux/module.h>
 
 #include <linux/poll.h>
+#include <linux/smp_lock.h>
 #include <linux/types.h>
 #include <linux/stddef.h>
 #include <linux/timer.h>
@@ -1544,10 +1545,12 @@ static int do_open(struct inode *inode, struct file *filp)
 {
 	struct apm_user *as;
 
+	lock_kernel();
 	as = kmalloc(sizeof(*as), GFP_KERNEL);
 	if (as == NULL) {
 		printk(KERN_ERR "apm: cannot allocate struct of size %d bytes\n",
 		       sizeof(*as));
+		       unlock_kernel();
 		return -ENOMEM;
 	}
 	as->magic = APM_BIOS_MAGIC;
@@ -1569,6 +1572,7 @@ static int do_open(struct inode *inode, struct file *filp)
 	user_list = as;
 	spin_unlock(&user_list_lock);
 	filp->private_data = as;
+	unlock_kernel();
 	return 0;
 }