Generic lock-free kmalloc cache implementation

Conflicts:
	kernel/mem.c

kernel/mem.c

@@ -2611,3 +2611,60 @@ int ihk_mc_get_mem_user_page(void *arg0, page_table_t pt, pte_t *ptep, void *pga
 
 	return 0;
 }
+
+/*
+ * Generic lockless kmalloc cache.
+ */
+void *kmalloc_cache_alloc(struct kmalloc_cache_header *cache,
+		size_t size)
+{
+	struct kmalloc_cache_header *first, *next;
+
+retry:
+	next = NULL;
+	first = cache->next;
+
+	if (first) {
+		next = first->next;
+
+		if (!__sync_bool_compare_and_swap(&cache->next,
+					first, next)) {
+			goto retry;
+		}
+	}
+	else {
+		int i;
+		kprintf("%s: cache empty, allocating ...\n", __FUNCTION__);
+		for (i = 0; i < 100; ++i) {
+			first = (struct kmalloc_cache_header *)
+				kmalloc(size, IHK_MC_AP_NOWAIT);
+
+			if (!first) {
+				kprintf("%s: ERROR: allocating cache element\n", __FUNCTION__);
+				continue;
+			}
+
+			kmalloc_cache_free(cache, first);
+		}
+
+		goto retry;
+	}
+
+	return (void *)first;
+}
+
+void kmalloc_cache_free(struct kmalloc_cache_header *cache, void *elem)
+{
+	struct kmalloc_cache_header *current = NULL;
+	struct kmalloc_cache_header *new =
+		(struct kmalloc_cache_header *)elem;
+
+retry:
+	current = cache->next;
+	new->next = current;
+
+	if (!__sync_bool_compare_and_swap(&cache->next, current, new)) {
+		goto retry;
+	}
+}
+