[Tarantool-patches] [PATCH 1/2] fiber: unref fiber.storage via global Lua state
Vladislav Shpilevoy
v.shpilevoy at tarantool.org
Sun Dec 8 22:28:32 MSK 2019
Fiber.storage is a table, available from anywhere in the fiber. It
is destroyed after fiber function is finished. That provides a
reliable fiber-local storage, similar to thread-local in C/C++.
But there is a problem that the storage may be created via one
struct lua_State, and destroyed via another. Here is an example:
function test_storage()
fiber.self().storage.key = 100
end
box.schema.func.create('test_storage')
_ = fiber.create(function()
box.func.test_storage:call()
end)
There are 3 struct lua_State:
tarantool_L - global always alive Lua state;
L1 - stack of the fiber, created by fiber.create();
L2 - stack created by that fiber to execute test_storage().
Fiber.storage is created on stack of L2 and referenced by global
LUA_REGISTRYINDEX. Then it is unreferenced from L1 when the fiber
is being destroyed.
That is generally ok as soon as the storage object is always in
LUA_REGISTRYINDEX, which is shared by all Lua states.
But soon during destruction of the fiber.storage there will be
only tarantool_L and the original L2. Original L2 may be already
deleted by the time the storage is being destroyed. So this patch
makes unref of the storage via reliable tarantool_L.
Needed for #4662
---
src/lua/fiber.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/lua/fiber.c b/src/lua/fiber.c
index 53ebec9aa..a7b75f9bf 100644
--- a/src/lua/fiber.c
+++ b/src/lua/fiber.c
@@ -445,7 +445,7 @@ lua_fiber_run_f(MAYBE_UNUSED va_list ap)
/* Destroy local storage */
int storage_ref = f->storage.lua.ref;
if (storage_ref > 0)
- luaL_unref(L, LUA_REGISTRYINDEX, storage_ref);
+ luaL_unref(tarantool_L, LUA_REGISTRYINDEX, storage_ref);
/*
* If fiber is not joinable
* We can unref child stack here,
--
2.21.0 (Apple Git-122.2)
More information about the Tarantool-patches
mailing list