Re: [Tarantool-patches] [PATCH v2] refactoring: wrap lua_newthread using luaT_cpcall

[Igor Munkin <imun@tarantool.org>]

CCed Sergos for proceeding with the review.

On 17.10.19, Igor Munkin wrote:
> Ilya,
> 
> Thanks, the patch LGTM, however please consider my minor comments.
> 
> On 17.10.19, Ilya Kosarev wrote:
> > Wrap throwing lua_newthread in luaT_newthread using luaT_cpcall
> > to process arising error properly.
> > 
> > Closes #4556
> > ---
> > https://github.com/tarantool/tarantool/tree/i.kosarev/gh-4556-wrap-lua-newthread
> > https://github.com/tarantool/tarantool/issues/4556
> > 
> > Changes in v2:
> > - introduced luaT_newthread instead of repeated slocs
> > - renamed luaL_pushthread to luaT_pushthread due to namespaces agreement
> > 
> >  src/box/lua/call.c            | 12 +++++++---
> >  src/lua/fiber.c               |  4 +++-
> >  src/lua/trigger.c             | 12 ++++------
> >  src/lua/utils.h               | 41 +++++++++++++++++++++++++++++++++++
> >  third_party/lua-yaml/lyaml.cc |  5 ++++-
> >  5 files changed, 61 insertions(+), 13 deletions(-)
> > 
> > diff --git a/src/box/lua/call.c b/src/box/lua/call.c
> > index 631003c84..51cad286a 100644
> > --- a/src/box/lua/call.c
> > +++ b/src/box/lua/call.c
> > @@ -527,7 +527,9 @@ static inline int
> >  box_process_lua(lua_CFunction handler, struct execute_lua_ctx *ctx,
> >  		struct port *ret)
> >  {
> > -	lua_State *L = lua_newthread(tarantool_L);
> > +	lua_State *L = luaT_newthread(tarantool_L);
> > +	if (L == NULL)
> > +		return -1;
> >  	int coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
> >  	port_lua_create(ret, L);
> >  	((struct port_lua *) ret)->ref = coro_ref;
> > @@ -654,7 +656,9 @@ func_persistent_lua_load(struct func_lua *func)
> >  	 * an arbitrary user-defined code
> >  	 * (e.g. body = 'fiber.yield()').
> >  	 */
> > -	struct lua_State *coro_L = lua_newthread(tarantool_L);
> > +	lua_State *coro_L = luaT_newthread(tarantool_L);
> > +	if (coro_L == NULL)
> > +		return -1;
> >  	if (!func->base.def->is_sandboxed) {
> >  		/*
> >  		 * Keep the original env to apply to a non-sandboxed
> > @@ -811,7 +815,9 @@ lbox_func_call(struct lua_State *L)
> >  	 * before the function call to pass it into the
> >  	 * pcall-sandboxed tarantool_L handler.
> >  	 */
> > -	lua_State *args_L = lua_newthread(tarantool_L);
> > +	lua_State *args_L = luaT_newthread(tarantool_L);
> > +	if (args_L == NULL)
> > +		return luaT_error(L);
> >  	int coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
> >  	lua_xmove(L, args_L, lua_gettop(L) - 1);
> >  	struct port args;
> > diff --git a/src/lua/fiber.c b/src/lua/fiber.c
> > index 336be60a2..124908a05 100644
> > --- a/src/lua/fiber.c
> > +++ b/src/lua/fiber.c
> > @@ -388,7 +388,9 @@ lua_fiber_run_f(MAYBE_UNUSED va_list ap)
> >  static struct fiber *
> >  fiber_create(struct lua_State *L)
> >  {
> > -	struct lua_State *child_L = lua_newthread(L);
> > +	lua_State *child_L = luaT_newthread(L);
> > +	if (child_L == NULL)
> > +		luaT_error(L);
> >  	int coro_ref = luaL_ref(L, LUA_REGISTRYINDEX);
> >  
> >  	struct fiber *f = fiber_new("lua", lua_fiber_run_f);
> > diff --git a/src/lua/trigger.c b/src/lua/trigger.c
> > index 4803e85c5..6df048a8d 100644
> > --- a/src/lua/trigger.c
> > +++ b/src/lua/trigger.c
> > @@ -73,17 +73,13 @@ lbox_trigger_run(struct trigger *ptr, void *event)
> >  	 * trigger yields, so when it's time to clean
> >  	 * up the coro, we wouldn't know which stack position
> >  	 * it is on.
> > -	 *
> > -	 * XXX: lua_newthread() may throw if out of memory,
> > -	 * this needs to be wrapped with lua_pcall() as well.
> > -	 * Don't, since it's a stupid overhead on every trigger
> > -	 * invocation, and in future we plan to hack into Lua
> > -	 * C API to fix this.
> >  	 */
> > -	struct lua_State *L;
> > +	lua_State *L;
> >  	int coro_ref;
> >  	if (fiber()->storage.lua.stack == NULL) {
> > -		L = lua_newthread(tarantool_L);
> > +		L = luaT_newthread(tarantool_L);
> > +		if (L == NULL)
> > +			diag_raise();
> >  		coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
> >  	} else {
> >  		L = fiber()->storage.lua.stack;
> > diff --git a/src/lua/utils.h b/src/lua/utils.h
> > index f8c34545a..f82b30fbc 100644
> > --- a/src/lua/utils.h
> > +++ b/src/lua/utils.h
> > @@ -591,6 +591,47 @@ luaL_checkfinite(struct lua_State *L, struct luaL_serializer *cfg,
> >  		luaL_error(L, "number must not be NaN or Inf");
> >  }
> >  
> 
> Note: the comment about lua_* namespace also relates to the wrapper
> below. I guess we need some follow-up activity for it.
> 
> > +/**
> > + * @brief A wrapper for lua_newthread() to pass it into luaT_cpcall
> > + * @param L is a Lua State
> > + * @sa lua_newthread()
> > + */
> > +static inline int
> > +lua_newthread_wrapper(lua_State *L)
> > +{
> > +	*(lua_State **)lua_touserdata(L, 1) = lua_newthread(L);
> > +	return 0;
> > +}
> > +
> 
> Minor: I see no reason to create a separate function for pushing one
> lua_State onto the anothers' stack. Feel free to ignore or to discuss it
> with the next reviewer.
> 
> > +/**
> > + * @brief Push L1 thread onto the L stack
> > + * @param L is a Lua State whose stack we are pushing onto
> > + * @param L1 is a Lua State whose thread we are pushing
> > + */
> > +static inline void
> > +luaT_pushthread(lua_State *L, lua_State *L1)
> > +{
> > +	setthreadV(L, L->top, L1);
> > +	incr_top(L);
> > +}
> > +
> > +/**
> > + * @brief Safe wrapper for lua_newthread()
> > + * @param L is a Lua State
> > + * @sa lua_newthread()
> > + */
> > +static inline lua_State *
> > +luaT_newthread(lua_State *L)
> > +{
> > +	lua_State *L1 = NULL;
> > +	if (luaT_cpcall(L, lua_newthread_wrapper, &L1) != 0) {
> > +		return NULL;
> > +	}
> > +	assert(L1 != NULL);
> > +	luaT_pushthread(L, L1);
> > +	return L1;
> > +}
> > +
> >  /**
> >   * Check if a value on @a L stack by index @a idx is an ibuf
> >   * object. Both 'struct ibuf' and 'struct ibuf *' are accepted.
> > diff --git a/third_party/lua-yaml/lyaml.cc b/third_party/lua-yaml/lyaml.cc
> > index 7485341fa..af4f2f5d5 100644
> > --- a/third_party/lua-yaml/lyaml.cc
> > +++ b/third_party/lua-yaml/lyaml.cc
> > @@ -789,7 +789,10 @@ lua_yaml_encode(lua_State *L, struct luaL_serializer *serializer,
> >     dumper.cfg = serializer;
> >     dumper.error = 0;
> >     /* create thread to use for YAML buffer */
> > -   dumper.outputL = lua_newthread(L);
> > +   dumper.outputL = luaT_newthread(L);
> > +   if (dumper.outputL == NULL) {
> > +      return luaL_error(L, OOM_ERRMSG);
> > +   }
> >     luaL_buffinit(dumper.outputL, &dumper.yamlbuf);
> >  
> >     if (!yaml_emitter_initialize(&dumper.emitter))
> > -- 
> > 2.17.1
> > 
> 
> -- 
> Best regards,
> IM

-- 
Best regards,
IM