From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp15.mail.ru (smtp15.mail.ru [94.100.176.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dev.tarantool.org (Postfix) with ESMTPS id 0C57B44643D for ; Fri, 25 Sep 2020 00:01:16 +0300 (MSK) From: Timur Safin Date: Fri, 25 Sep 2020 00:00:37 +0300 Message-Id: <064abe8c26b65283e1e7e591796f779ea4b42b4b.1600955796.git.tsafin@tarantool.org> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: [Tarantool-patches] [PATCH 1.10 5/9] module api: luaT_temp_luastate & luaT_release_temp_luastate List-Id: Tarantool development patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: v.shpilevoy@tarantool.org, alexander.turenko@tarantool.org Cc: tarantool-patches@dev.tarantool.org 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/lua/utils.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ src/lua/utils.h | 35 +++++++++++++++++++++++++++++++++++ 2 files changed, 84 insertions(+) diff --git a/src/lua/utils.c b/src/lua/utils.c index e555607cf..58c54f8fb 100644 --- a/src/lua/utils.c +++ b/src/lua/utils.c @@ -1090,6 +1090,55 @@ 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 a818e5eee..4eb5ce566 100644 --- a/src/lua/utils.h +++ b/src/lua/utils.h @@ -530,6 +530,41 @@ 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 */ void -- 2.20.1