[Tarantool-patches] [PATCH 2.X 5/7] module api: luaT_temp_luastate & luaT_release_temp_luastate
Timur Safin
tsafin at tarantool.org
Thu Sep 24 20:00:18 MSK 2020
Moved `luaT_temp_luastate` & `luaT_release_temp_luastate` from
merger to ustil.c and made them public.
They were necessary for external merger support.
Part of #5273
---
src/box/lua/merger.c | 78 --------------------------------------------
src/exports.h | 2 ++
src/lua/utils.c | 49 ++++++++++++++++++++++++++++
src/lua/utils.h | 35 ++++++++++++++++++++
4 files changed, 86 insertions(+), 78 deletions(-)
diff --git a/src/box/lua/merger.c b/src/box/lua/merger.c
index 583946c4c..f26594049 100644
--- a/src/box/lua/merger.c
+++ b/src/box/lua/merger.c
@@ -149,84 +149,6 @@ luaT_gettuple(struct lua_State *L, int idx, struct tuple_format *format)
return tuple;
}
-/**
- * Get a temporary Lua state.
- *
- * Use case: a function does not accept a Lua state as an argument
- * to allow using from C code, but uses a Lua value, which is
- * referenced in LUA_REGISTRYINDEX. A temporary Lua stack is needed
- * to get and process the value.
- *
- * The resulting Lua state has a separate Lua stack, but the same
- * globals and registry as `tarantool_L` (and all Lua states in
- * tarantool at the moment of writing this).
- *
- * This Lua state should be used only from one fiber: otherwise
- * one fiber may change the stack and another one will access a
- * wrong stack slot when it will be scheduled for execution after
- * yield.
- *
- * Return a Lua state on success and set @a coro_ref and @a top.
- * These values should be passed to
- * `luaT_release_temp_luastate()`, when the state is not needed
- * anymore.
- *
- * Return NULL and set a diag at failure.
- */
-static struct lua_State *
-luaT_temp_luastate(int *coro_ref, int *top)
-{
- if (fiber()->storage.lua.stack != NULL) {
- /*
- * Reuse existing stack. In the releasing function
- * we should drop a stack top to its initial
- * value to don't exhaust available slots by
- * many requests in row.
- */
- struct lua_State *L = fiber()->storage.lua.stack;
- *coro_ref = LUA_NOREF;
- *top = lua_gettop(L);
- return L;
- }
-
- /* Popped by luaL_ref(). */
- struct lua_State *L = luaT_newthread(tarantool_L);
- if (L == NULL)
- return NULL;
- /*
- * We should remove the reference to the newly created Lua
- * thread from tarantool_L, because of two reasons:
- *
- * First, if we'll push something to tarantool_L and
- * yield, then another fiber will not know that a stack
- * top is changed and may operate on a wrong slot.
- *
- * Second, many requests that push a value to tarantool_L
- * and yield may exhaust available slots on the stack. It
- * is limited by LUAI_MAXSTACK build time constant (~65K).
- *
- * We cannot just pop the value, but should keep the
- * reference in the registry while it is in use.
- * Otherwise it may be garbage collected.
- */
- *coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
- *top = -1;
- return L;
-}
-
-/**
- * Release a temporary Lua state.
- *
- * It complements `luaT_temp_luastate()`.
- */
-static void
-luaT_release_temp_luastate(struct lua_State *L, int coro_ref, int top)
-{
- if (top >= 0)
- lua_settop(L, top);
- luaL_unref(tarantool_L, LUA_REGISTRYINDEX, coro_ref);
-}
-
/* }}} */
/* {{{ Create, destroy structures from Lua */
diff --git a/src/exports.h b/src/exports.h
index 1c16e88b2..ef4f3b741 100644
--- a/src/exports.h
+++ b/src/exports.h
@@ -416,7 +416,9 @@ EXPORT(luaT_error)
EXPORT(luaT_istuple)
EXPORT(luaT_newthread)
EXPORT(luaT_pushtuple)
+EXPORT(luaT_release_temp_luastate)
EXPORT(luaT_state)
+EXPORT(luaT_temp_luastate)
EXPORT(luaT_tolstring)
EXPORT(luaT_tuple_encode)
EXPORT(luaT_tuple_new)
diff --git a/src/lua/utils.c b/src/lua/utils.c
index bf5452d3e..40078b5df 100644
--- a/src/lua/utils.c
+++ b/src/lua/utils.c
@@ -1259,6 +1259,55 @@ luaT_newthread(struct lua_State *L)
return L1;
}
+struct lua_State *
+luaT_temp_luastate(int *coro_ref, int *top)
+{
+ if (fiber()->storage.lua.stack != NULL) {
+ /*
+ * Reuse existing stack. In the releasing function
+ * we should drop a stack top to its initial
+ * value to don't exhaust available slots by
+ * many requests in row.
+ */
+ struct lua_State *L = fiber()->storage.lua.stack;
+ *coro_ref = LUA_NOREF;
+ *top = lua_gettop(L);
+ return L;
+ }
+
+ /* Popped by luaL_ref(). */
+ struct lua_State *L = luaT_newthread(tarantool_L);
+ if (L == NULL)
+ return NULL;
+ /*
+ * We should remove the reference to the newly created Lua
+ * thread from tarantool_L, because of two reasons:
+ *
+ * First, if we'll push something to tarantool_L and
+ * yield, then another fiber will not know that a stack
+ * top is changed and may operate on a wrong slot.
+ *
+ * Second, many requests that push a value to tarantool_L
+ * and yield may exhaust available slots on the stack. It
+ * is limited by LUAI_MAXSTACK build time constant (~65K).
+ *
+ * We cannot just pop the value, but should keep the
+ * reference in the registry while it is in use.
+ * Otherwise it may be garbage collected.
+ */
+ *coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
+ *top = -1;
+ return L;
+}
+
+void
+luaT_release_temp_luastate(struct lua_State *L, int coro_ref, int top)
+{
+ if (top >= 0)
+ lua_settop(L, top);
+ luaL_unref(tarantool_L, LUA_REGISTRYINDEX, coro_ref);
+}
+
int
tarantool_lua_utils_init(struct lua_State *L)
{
diff --git a/src/lua/utils.h b/src/lua/utils.h
index 9b1fe7e57..da0140076 100644
--- a/src/lua/utils.h
+++ b/src/lua/utils.h
@@ -554,6 +554,41 @@ luaL_iscallable(lua_State *L, int idx);
struct lua_State *
luaT_newthread(struct lua_State *L);
+/**
+ * Get a temporary Lua state.
+ *
+ * Use case: a function does not accept a Lua state as an argument
+ * to allow using from C code, but uses a Lua value, which is
+ * referenced in LUA_REGISTRYINDEX. A temporary Lua stack is needed
+ * to get and process the value.
+ *
+ * The resulting Lua state has a separate Lua stack, but the same
+ * globals and registry as `tarantool_L` (and all Lua states in
+ * tarantool at the moment of writing this).
+ *
+ * This Lua state should be used only from one fiber: otherwise
+ * one fiber may change the stack and another one will access a
+ * wrong stack slot when it will be scheduled for execution after
+ * yield.
+ *
+ * Return a Lua state on success and set @a coro_ref and @a top.
+ * These values should be passed to
+ * `luaT_release_temp_luastate()`, when the state is not needed
+ * anymore.
+ *
+ * Return NULL and set a diag at failure.
+ */
+struct lua_State *
+luaT_temp_luastate(int *coro_ref, int *top);
+
+/**
+ * Release a temporary Lua state.
+ *
+ * It complements `luaT_temp_luastate()`.
+ */
+void
+luaT_release_temp_luastate(struct lua_State *L, int coro_ref, int top);
+
/** \endcond public */
/**
--
2.20.1
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