cpg_dispatch requires 0x101568 bytes of stack.

diff --git a/lib/coroutine.c b/lib/coroutine.c
index 5b2ed79..1e1060c 100644
--- a/lib/coroutine.c
+++ b/lib/coroutine.c
@@ -52,7 +52,7 @@ enum co_action {
 #define POOL_MAX_SIZE   64
 #endif
 
-#define STACK_MAX_SIZE (1 << 20)  /* 1 MB */
+#define STACK_MAX_SIZE (2 << 20)  /* 1 MB */
 
 struct coroutine {
 	coroutine_entry_func_t *entry;