diff --git a/include/l4/lib/idpool.h b/include/l4/lib/idpool.h
index c3d9668..619f237 100644
--- a/include/l4/lib/idpool.h
+++ b/include/l4/lib/idpool.h
@@ -2,8 +2,10 @@
 #define __IDPOOL_H__
 
 #include <l4/lib/bit.h>
+#include <l4/lib/spinlock.h>
 
 struct id_pool {
+	struct spinlock lock;
 	int nwords;
 	u32 bitmap[];
 };
diff --git a/src/lib/idpool.c b/src/lib/idpool.c
index 3745dd3..59f033e 100644
--- a/src/lib/idpool.c
+++ b/src/lib/idpool.c
@@ -1,7 +1,7 @@
 /*
  * Used for thread and space ids.
  *
- * Copyright (C) 2007 Bahadir Balban
+ * Copyright (C) 2007, 2008 Bahadir Balban
  */
 #include <l4/lib/printk.h>
 #include <l4/lib/idpool.h>
@@ -13,21 +13,31 @@ struct id_pool *id_pool_new_init(int totalbits)
 	int nwords = BITWISE_GETWORD(totalbits);
 	struct id_pool *new = kzalloc((nwords * SZ_WORD)
 				      + sizeof(struct id_pool));
+	spin_lock_init(&new->lock);
 	new->nwords = nwords;
 	return new;
 }
 
 int id_new(struct id_pool *pool)
 {
-	int id = find_and_set_first_free_bit(pool->bitmap,
+	int id;
+
+	spin_lock(&pool->lock);
+	id = find_and_set_first_free_bit(pool->bitmap,
 					     pool->nwords * WORD_BITS);
+	spin_unlock(&pool->lock);
 	BUG_ON(id < 0);
+
 	return id;
 }
 
 int id_del(struct id_pool *pool, int id)
 {
-	int ret = check_and_clear_bit(pool->bitmap, id);
+	int ret;
+
+	spin_lock(&pool->lock);
+	ret = check_and_clear_bit(pool->bitmap, id);
+	spin_unlock(&pool->lock);
 
 	BUG_ON(ret < 0);
 	return ret;
@@ -36,7 +46,11 @@ int id_del(struct id_pool *pool, int id)
 /* Return a specific id, if available */
 int id_get(struct id_pool *pool, int id)
 {
-	int ret = check_and_set_bit(pool->bitmap, id);
+	int ret;
+
+	spin_lock(&pool->lock);
+	ret = check_and_set_bit(pool->bitmap, id);
+	spin_unlock(&pool->lock);
 
 	if (ret < 0)
 		return ret;