diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index dfdec524d1b..3db49b9ca37 100644
--- a/kernel/pm_qos_params.c
+++ b/kernel/pm_qos_params.c
@@ -29,7 +29,6 @@
 
 #include <linux/pm_qos_params.h>
 #include <linux/sched.h>
-#include <linux/smp_lock.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/time.h>
@@ -344,37 +343,33 @@ int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 }
 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 
-#define PID_NAME_LEN sizeof("process_1234567890")
-static char name[PID_NAME_LEN];
+#define PID_NAME_LEN 32
 
 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 {
 	int ret;
 	long pm_qos_class;
+	char name[PID_NAME_LEN];
 
-	lock_kernel();
 	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 	if (pm_qos_class >= 0) {
 		filp->private_data = (void *)pm_qos_class;
-		sprintf(name, "process_%d", current->pid);
+		snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
 		ret = pm_qos_add_requirement(pm_qos_class, name,
 					PM_QOS_DEFAULT_VALUE);
-		if (ret >= 0) {
-			unlock_kernel();
+		if (ret >= 0)
 			return 0;
-		}
 	}
-	unlock_kernel();
-
 	return -EPERM;
 }
 
 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 {
 	int pm_qos_class;
+	char name[PID_NAME_LEN];
 
 	pm_qos_class = (long)filp->private_data;
-	sprintf(name, "process_%d", current->pid);
+	snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
 	pm_qos_remove_requirement(pm_qos_class, name);
 
 	return 0;
@@ -385,13 +380,14 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 {
 	s32 value;
 	int pm_qos_class;
+	char name[PID_NAME_LEN];
 
 	pm_qos_class = (long)filp->private_data;
 	if (count != sizeof(s32))
 		return -EINVAL;
 	if (copy_from_user(&value, buf, sizeof(s32)))
 		return -EFAULT;
-	sprintf(name, "process_%d", current->pid);
+	snprintf(name, PID_NAME_LEN, "process_%d", current->pid);
 	pm_qos_update_requirement(pm_qos_class, name, value);
 
 	return  sizeof(s32);
diff --git a/kernel/sys.c b/kernel/sys.c
index 9968c5fb55b..585d6cd1004 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -8,7 +8,6 @@
 #include <linux/mm.h>
 #include <linux/utsname.h>
 #include <linux/mman.h>
-#include <linux/smp_lock.h>
 #include <linux/notifier.h>
 #include <linux/reboot.h>
 #include <linux/prctl.h>
@@ -349,6 +348,9 @@ void kernel_power_off(void)
 	machine_power_off();
 }
 EXPORT_SYMBOL_GPL(kernel_power_off);
+
+static DEFINE_MUTEX(reboot_mutex);
+
 /*
  * Reboot system call: for obvious reasons only root may call it,
  * and even root needs to set up some magic numbers in the registers
@@ -381,7 +383,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 	if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
 		cmd = LINUX_REBOOT_CMD_HALT;
 
-	lock_kernel();
+	mutex_lock(&reboot_mutex);
 	switch (cmd) {
 	case LINUX_REBOOT_CMD_RESTART:
 		kernel_restart(NULL);
@@ -397,20 +399,18 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 
 	case LINUX_REBOOT_CMD_HALT:
 		kernel_halt();
-		unlock_kernel();
 		do_exit(0);
 		panic("cannot halt");
 
 	case LINUX_REBOOT_CMD_POWER_OFF:
 		kernel_power_off();
-		unlock_kernel();
 		do_exit(0);
 		break;
 
 	case LINUX_REBOOT_CMD_RESTART2:
 		if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
-			unlock_kernel();
-			return -EFAULT;
+			ret = -EFAULT;
+			break;
 		}
 		buffer[sizeof(buffer) - 1] = '\0';
 
@@ -433,7 +433,7 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 		ret = -EINVAL;
 		break;
 	}
-	unlock_kernel();
+	mutex_unlock(&reboot_mutex);
 	return ret;
 }