Hello.
I'm trying to understand Lua 5.1 multi-threading support.
I understand that lua_lock and lua_unlock macroses is intended to prevent concurrent access to lua_State, but what about Lua _G table?
I think one mutex per one lua_State* (created with lua_newthread or luaL_newstate) is enough. And if so, then how Lua _G table will be shared among 2 system threads calling lua_pcall?
I mean, how lua_lock & lua_unlock usually implemented to make the C++ code below run correctly? (output will contain 10000 values between 0..10000 in ascending order with duplicates, but lua_States from different system threads will access correctly to _G.tbl.value)
And does redefinition of lua_lock & lua_unlock is enough to make Lua multithreaded?
void threadfunc(lua_State* L) {
lua_pushstring("threadfunc");
lua_pcall(L, 1, 0);
}
void main() {
lua_State *global = luaL_newstate();
luaL_openlibs(global);
// loading some script with "require" call
/* script code:
tbl = { value = 0 };
function threadfunc()
for i=1,10000 do
tbl.value = i
end
end
function mainfunc()
for i=1,10000 do
print(tbl.value);
end
end
*/
lua_State* luathread = lua_newthread(global);
std::thread thread(&threadfunc, luathread);
lua_pushstring("mainfunc");
lua_pcall(L, 1, 0);
thread.join();
lua_close(global);
}
