diff --git a/executer/kernel/mcctrl/arch/x86_64/archdeps.c b/executer/kernel/mcctrl/arch/x86_64/archdeps.c
index 5fab8133..2179f160 100644
--- a/executer/kernel/mcctrl/arch/x86_64/archdeps.c
+++ b/executer/kernel/mcctrl/arch/x86_64/archdeps.c
@@ -64,6 +64,8 @@ reserve_user_space(struct mcctrl_usrdata *usrdata, unsigned long *startp, unsign
 	unsigned long start = 0L;
 	unsigned long end;
 
+	mutex_lock(&usrdata->reserve_lock);
+
 #define	DESIRED_USER_END	0x800000000000
 #define	GAP_FOR_MCEXEC		0x008000000000UL
 	end = DESIRED_USER_END;
@@ -81,6 +83,8 @@ reserve_user_space(struct mcctrl_usrdata *usrdata, unsigned long *startp, unsign
 	up_write(&current->mm->mmap_sem);
 #endif
 
+	mutex_unlock(&usrdata->reserve_lock);
+
 	if (IS_ERR_VALUE(start)) {
 		return start;
 	}
diff --git a/executer/kernel/mcctrl/ikc.c b/executer/kernel/mcctrl/ikc.c
index 461a23be..780fe031 100644
--- a/executer/kernel/mcctrl/ikc.c
+++ b/executer/kernel/mcctrl/ikc.c
@@ -289,6 +289,7 @@ int prepare_ikc_channels(ihk_os_t os)
 	memcpy(&usrdata->listen_param2, &listen_param2, sizeof listen_param2);
 	ihk_ikc_listen_port(os, &usrdata->listen_param2);
 	init_waitqueue_head(&usrdata->wq_procfs);
+	mutex_init(&usrdata->reserve_lock);
 
 	for (i = 0; i < MCCTRL_PER_PROC_DATA_HASH_SIZE; ++i) {
 		INIT_LIST_HEAD(&usrdata->per_proc_data_hash[i]);
diff --git a/executer/kernel/mcctrl/mcctrl.h b/executer/kernel/mcctrl/mcctrl.h
index 09aca82e..542f1f95 100644
--- a/executer/kernel/mcctrl/mcctrl.h
+++ b/executer/kernel/mcctrl/mcctrl.h
@@ -283,6 +283,7 @@ struct mcctrl_usrdata {
 	int	base_cpu;
 	int	job_pos;
 	int	mcctrl_dma_abort;
+	struct mutex reserve_lock;
 	unsigned long	last_thread_exec;
 	wait_queue_head_t wq_procfs;
 	struct list_head per_proc_data_hash[MCCTRL_PER_PROC_DATA_HASH_SIZE];