diff --git a/kernel/include/xpmem.h b/kernel/include/xpmem.h
index 5c3fb330..52cb244b 100644
--- a/kernel/include/xpmem.h
+++ b/kernel/include/xpmem.h
@@ -28,5 +28,17 @@ int xpmem_remove_process_memory_range(struct process_vm *vm,
 int xpmem_fault_process_memory_range(struct process_vm *vm,
 	struct vm_range *vmr, unsigned long vaddr, uint64_t reason);
 
+struct xpmem_attachment {
+	ihk_rwspinlock_t at_lock;	/* att lock */
+	unsigned long vaddr;	/* starting address of seg attached */
+	unsigned long at_vaddr;	/* address where seg is attached */
+	size_t at_size;		/* size of seg attachment */
+	struct vm_range *at_vmr;	/* vm_range where seg is attachment */
+	int flags;	/* att attributes and state */
+	ihk_atomic_t refcnt;	/* references to att */
+	struct xpmem_access_permit *ap;	/* associated access permit */
+	struct list_head att_list;	/* atts linked to access permit */
+	struct process_vm *vm;	/* process_vm attached to */
+};
 #endif /* _XPMEM_H */
 
diff --git a/kernel/include/xpmem_private.h b/kernel/include/xpmem_private.h
index c47498e3..dc2853ff 100644
--- a/kernel/include/xpmem_private.h
+++ b/kernel/include/xpmem_private.h
@@ -177,19 +177,6 @@ struct xpmem_access_permit {
 	struct list_head ap_hashlist;	/* access permit hash list */
 };
 
-struct xpmem_attachment {
-	mcs_rwlock_lock_t at_lock;	/* att lock */
-	unsigned long vaddr;	/* starting address of seg attached */
-	unsigned long at_vaddr;	/* address where seg is attached */
-	size_t at_size;		/* size of seg attachment */
-	struct vm_range *at_vmr;	/* vm_range where seg is attachment */
-	volatile int flags;	/* att attributes and state */
-	ihk_atomic_t refcnt;	/* references to att */
-	struct xpmem_access_permit *ap;	/* associated access permit */
-	struct list_head att_list;	/* atts linked to access permit */
-	struct process_vm *vm;	/* process_vm attached to */
-};
-
 struct xpmem_partition {
 	ihk_atomic_t n_opened;	/* # of /dev/xpmem opened */
 	struct xpmem_hashlist tg_hashtable[];	/* locks + tg hash lists */
diff --git a/kernel/xpmem.c b/kernel/xpmem.c
index cfbbae32..7503c8c0 100644
--- a/kernel/xpmem.c
+++ b/kernel/xpmem.c
@@ -1010,7 +1010,7 @@ static int xpmem_attach(
 	struct xpmem_access_permit *ap;
 	struct xpmem_segment *seg;
 	struct xpmem_attachment *att;
-	struct mcs_rwlock_node_irqsave at_lock;
+	unsigned long at_lock;
 	struct vm_range *vmr;
 	struct process_vm *vm = cpu_local_var(current)->vm;
 
@@ -1086,7 +1086,7 @@ static int xpmem_attach(
 	XPMEM_DEBUG("kmalloc(): att=0x%p", att);
 	memset(att, 0, sizeof(struct xpmem_attachment));
 
-	mcs_rwlock_init(&att->at_lock);
+	ihk_rwspinlock_init(&att->at_lock);
 	att->vaddr = seg_vaddr;
 	att->at_size = size;
 	att->ap = ap;
@@ -1096,7 +1096,7 @@ static int xpmem_attach(
         xpmem_att_not_destroyable(att);
         xpmem_att_ref(att);
 
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 	ihk_mc_spinlock_lock_noirq(&ap->lock);
 	list_add_tail(&att->att_list, &ap->att_list);
@@ -1180,7 +1180,7 @@ out_2:
 		ihk_mc_spinlock_unlock_noirq(&ap->lock);
 		xpmem_att_destroyable(att);
 	}
-	mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+	ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 	xpmem_att_deref(att);
 out_1:
 	xpmem_ap_deref(ap);
@@ -1200,7 +1200,7 @@ static int xpmem_detach(
 	int ret;
 	struct xpmem_access_permit *ap;
 	struct xpmem_attachment *att;
-	struct mcs_rwlock_node_irqsave at_lock;
+	unsigned long at_lock;
 	struct vm_range *range;
 	struct process_vm *vm = cpu_local_var(current)->vm;
 
@@ -1223,10 +1223,10 @@ static int xpmem_detach(
 
 	xpmem_att_ref(att);
 
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 	if (att->flags & XPMEM_FLAG_DESTROYING) {
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 		ihk_rwspinlock_write_unlock_noirq(&vm->memory_range_lock);
 		xpmem_att_deref(att);
 		return 0;
@@ -1239,7 +1239,7 @@ static int xpmem_detach(
 	if (cpu_local_var(current)->proc->pid != ap->tg->tgid) {
 		att->flags &= ~XPMEM_FLAG_DESTROYING;
 		xpmem_ap_deref(ap);
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 		ihk_rwspinlock_write_unlock_noirq(&vm->memory_range_lock);
 		xpmem_att_deref(att);
 		return -EACCES;
@@ -1251,7 +1251,7 @@ static int xpmem_detach(
     /* range->memobj is released in xpmem_vm_munmap() --> xpmem_remove_process_range() -->
 	   xpmem_free_process_memory_range() */
 
-	mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+	ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 
 	XPMEM_DEBUG("xpmem_vm_munmap(): start=0x%lx, len=0x%lx", 
 		range->start, att->at_size);
@@ -1419,16 +1419,16 @@ static void xpmem_detach_att(
 	int ret;
 	struct vm_range *range;
 	struct process_vm *vm;
-	struct mcs_rwlock_node_irqsave at_lock;
+	unsigned long at_lock;
 
 	XPMEM_DEBUG("call: apid=0x%lx, att=0x%p", ap->apid, att);
 
 	XPMEM_DEBUG("detaching att->vm=0x%p", (void *)att->vm);
 
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 	if (att->flags & XPMEM_FLAG_DESTROYING) {
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 		XPMEM_DEBUG("return: XPMEM_FLAG_DESTROYING");
 		return;
 	}
@@ -1444,7 +1444,7 @@ static void xpmem_detach_att(
 		ihk_mc_spinlock_lock_noirq(&ap->lock);
 		list_del_init(&att->att_list);
 		ihk_mc_spinlock_unlock_noirq(&ap->lock);
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 		ihk_rwspinlock_read_unlock_noirq(&vm->memory_range_lock);
 		xpmem_att_destroyable(att);
 		XPMEM_DEBUG("return: range=%p");
@@ -1470,7 +1470,7 @@ static void xpmem_detach_att(
 	list_del_init(&att->att_list);
 	ihk_mc_spinlock_unlock_noirq(&ap->lock);
 
-	mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+	ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 
 	XPMEM_DEBUG("xpmem_vm_munmap(): start=0x%lx, len=0x%lx", 
 		range->start, att->at_size);
@@ -1578,13 +1578,13 @@ static void xpmem_clear_PTEs_of_att(
 	unsigned long end)
 {
 	int ret;
-	struct mcs_rwlock_node_irqsave at_lock;
+	unsigned long at_lock;
 
 	XPMEM_DEBUG("call: att=0x%p, start=0x%lx, end=0x%lx", 
 		att, start, end);
 
 	ihk_rwspinlock_read_lock_noirq(&att->vm->memory_range_lock);
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 	if (att->flags & XPMEM_FLAG_VALIDPTEs) {
 		struct vm_range *range;
@@ -1624,7 +1624,7 @@ static void xpmem_clear_PTEs_of_att(
 			goto out;
 		}
 
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 
 		XPMEM_DEBUG(
 			"xpmem_vm_munmap(): start=0x%lx, len=0x%lx", 
@@ -1636,13 +1636,13 @@ static void xpmem_clear_PTEs_of_att(
 				__FUNCTION__, ret);
 		}
 
-		mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+		at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 		if (offset_start == 0 && att->at_size == invalidate_len)
 			att->flags &= ~XPMEM_FLAG_VALIDPTEs;
 	}
 out:
-	mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+	ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 	ihk_rwspinlock_read_unlock_noirq(&att->vm->memory_range_lock);
 
 	XPMEM_DEBUG("return: ");
@@ -1657,7 +1657,7 @@ int xpmem_remove_process_memory_range(
 	u64 remaining_vaddr;
 	struct xpmem_access_permit *ap;
 	struct xpmem_attachment *att;
-	struct mcs_rwlock_node_irqsave at_lock;
+	unsigned long at_lock;
 
 	XPMEM_DEBUG("call: vmr=0x%p, att=0x%p", vmr, vmr->private_data);
 
@@ -1671,7 +1671,7 @@ int xpmem_remove_process_memory_range(
 
 	xpmem_att_ref(att);
 
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
 
 	if (att->flags & XPMEM_FLAG_DESTROYING) {
 		XPMEM_DEBUG("already cleaned up");
@@ -1747,7 +1747,7 @@ int xpmem_remove_process_memory_range(
 	 */
 
 out:
-	mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+	ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 
 	xpmem_att_deref(att);
 
@@ -1773,7 +1773,7 @@ int xpmem_fault_process_memory_range(
 	struct xpmem_attachment *att;
 	struct xpmem_segment *seg;
 	size_t pgsize;
-	struct mcs_rwlock_node_irqsave at_lock = { 0 };
+	unsigned long at_lock;
 	int att_locked = 0;
 
 	XPMEM_DEBUG("call: vmr=0x%p, vaddr=0x%lx, reason=0x%lx", 
@@ -1804,15 +1804,15 @@ int xpmem_fault_process_memory_range(
 	seg_tg = seg->tg;
 	xpmem_tg_ref(seg_tg);
 
+	at_lock = ihk_rwspinlock_write_lock(&att->at_lock);
+	att_locked = 1;
+
 	if ((seg->flags & XPMEM_FLAG_DESTROYING) ||
 		(seg_tg->flags & XPMEM_FLAG_DESTROYING)) {
 		ret = -ENOENT;
 		goto out_2;
 	}
 
-	mcs_rwlock_writer_lock(&att->at_lock, &at_lock);
-	att_locked = 1;
-
 	if ((att->flags & XPMEM_FLAG_DESTROYING) ||
 		(ap_tg->flags & XPMEM_FLAG_DESTROYING) ||
 		(seg_tg->flags & XPMEM_FLAG_DESTROYING)) {
@@ -1865,7 +1865,7 @@ out_2:
 
 out_1:
 	if (att_locked) {
-		mcs_rwlock_writer_unlock(&att->at_lock, &at_lock);
+		ihk_rwspinlock_write_unlock(&att->at_lock, at_lock);
 	}
 
 	xpmem_tg_deref(seg_tg);