diff --git a/c/malloc_speed_test/pool_list.c b/c/malloc_speed_test/pool_list.c
index fa1f42a..2501e24 100644
--- a/c/malloc_speed_test/pool_list.c
+++ b/c/malloc_speed_test/pool_list.c
@@ -48,34 +48,37 @@ void init()
 
 #define MAX_B (pool + MAX_I * sizeof(struct block_s))
 
-inline void *alloc()
+inline void *pool_alloc()
 {
 	if (!free_pool)
 		return NULL;
 
-	if (busy_pool) {
-		free_pool->next = busy_pool;
+	free_pool->prev = free_pool->next; // save free_pool->next in free_pool->prev
+	
+	free_pool->next = busy_pool;
+
+	if (busy_pool)
 		busy_pool->prev = free_pool;
-	}
-	else
-		free_pool->next = NULL;
 
 	busy_pool = free_pool;
 
-	free_pool = free_pool->next;
+	free_pool = free_pool->prev;
+	
+	busy_pool->prev = NULL; // saved in free_pool->prev to NULL
 
 	return &busy_pool->obj;
 }
 
-inline void free(void *p)
+inline void pool_free(void *p)
 {
+	if (!p)
+		return;
+
 	struct block_s *b1 = (struct block_s *)(p - 2 * sizeof(struct block_s *)),
 	               *b0 = b1->prev,
 		       *b2 = b1->next,
 		       *f1 = free_pool;
 
-	// move one busy block to free list
-
 	// cut block from free list
 	if (b0)
 		b0->next = b2;
@@ -102,10 +105,18 @@ int main()
 {
 	unsigned long long i;
 
+	void *mem[MAX_I];
+
 	init();
 	
 	for (i = 0; i < MAX_I; i++)
-		alloc();
+		if (!(mem[i] = pool_alloc())) {
+			printf("не удалось выделить память под %lld блок\n", i);
+			break;
+		}
+
+	for (i = 0; i < MAX_I; i++)
+		pool_free(mem[i]);
 
 	return 0;
 }