LuaState: Fixed race condition in ref tracking. (#3529)
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@ -44,9 +44,69 @@ extern "C"
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const cLuaState::cRet cLuaState::Return = {};
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const cLuaState::cNil cLuaState::Nil = {};
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/** Each Lua state stores a pointer to its creating cLuaState in Lua globals, under this name.
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This way any cLuaState can reference the main cLuaState's TrackedCallbacks, mutex etc. */
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static const char * g_CanonLuaStateGlobalName = "_CuberiteInternal_CanonLuaState";
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////////////////////////////////////////////////////////////////////////////////
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// cCanonLuaStates:
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/** Tracks the canon cLuaState instances for each lua_State pointer.
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Used for tracked refs - the ref needs to be tracked by a single cLuaState (the canon state), despite being created from a different (attached) cLuaState.
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The canon state must be available without accessing the Lua state itself (so it cannot be stored within Lua). */
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class cCanonLuaStates
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{
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public:
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/** Returns the canon Lua state for the specified lua_State pointer. */
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static cLuaState * GetCanonState(lua_State * a_LuaState)
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{
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auto & inst = GetInstance();
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cCSLock lock(inst.m_CS);
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auto itr = inst.m_CanonStates.find(a_LuaState);
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if (itr == inst.m_CanonStates.end())
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{
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return nullptr;
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}
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return itr->second;
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}
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/** Adds a new canon cLuaState instance to the map.
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Used when a new Lua state is created, this informs the map that a new canon Lua state should be tracked. */
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static void Add(cLuaState & a_LuaState)
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{
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auto & inst = GetInstance();
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cCSLock lock(inst.m_CS);
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ASSERT(inst.m_CanonStates.find(a_LuaState) == inst.m_CanonStates.end());
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inst.m_CanonStates[a_LuaState.operator lua_State *()] = &a_LuaState;
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}
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/** Removes the bindings between the specified canon state and its lua_State pointer.
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Used when a Lua state is being closed. */
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static void Remove(cLuaState & a_LuaState)
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{
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auto & inst = GetInstance();
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cCSLock lock(inst.m_CS);
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auto itr = inst.m_CanonStates.find(a_LuaState);
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ASSERT(itr != inst.m_CanonStates.end());
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inst.m_CanonStates.erase(itr);
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}
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protected:
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/** The mutex protecting m_CanonStates against multithreaded access. */
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cCriticalSection m_CS;
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/** Map of lua_State pointers to their canon cLuaState instances. */
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std::map<lua_State *, cLuaState *> m_CanonStates;
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/** Returns the singleton instance of this class. */
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static cCanonLuaStates & GetInstance(void)
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{
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static cCanonLuaStates canonLuaStates;
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return canonLuaStates;
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}
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};
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@ -426,10 +486,7 @@ void cLuaState::Create(void)
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luaL_openlibs(m_LuaState);
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m_IsOwned = true;
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cLuaStateTracker::Add(*this);
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// Add the CanonLuaState value into the Lua state, so that we can get it from anywhere:
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lua_pushlightuserdata(m_LuaState, reinterpret_cast<void *>(this));
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lua_setglobal(m_LuaState, g_CanonLuaStateGlobalName);
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cCanonLuaStates::Add(*this);
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}
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@ -493,6 +550,7 @@ void cLuaState::Close(void)
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}
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}
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cCanonLuaStates::Remove(*this);
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cLuaStateTracker::Del(*this);
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lua_close(m_LuaState);
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m_LuaState = nullptr;
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@ -2146,15 +2204,9 @@ void cLuaState::LogStackValues(lua_State * a_LuaState, const char * a_Header)
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cLuaState * cLuaState::QueryCanonLuaState(void)
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cLuaState * cLuaState::QueryCanonLuaState(void) const
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{
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// Get the CanonLuaState global from Lua:
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auto cb = WalkToNamedGlobal(g_CanonLuaStateGlobalName);
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if (!cb.IsValid())
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{
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return nullptr;
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}
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return reinterpret_cast<cLuaState *>(lua_touserdata(m_LuaState, -1));
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return cCanonLuaStates::GetCanonState(m_LuaState);
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}
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@ -809,7 +809,7 @@ public:
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/** Returns the canon Lua state (the primary cLuaState instance that was used to create, rather than attach, the lua_State structure).
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Returns nullptr if the canon Lua state cannot be queried. */
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cLuaState * QueryCanonLuaState(void);
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cLuaState * QueryCanonLuaState(void) const;
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/** Outputs to log a warning about API call being unable to read its parameters from the stack,
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logs the stack trace and stack values. */
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@ -116,7 +116,7 @@ bool cLuaWindow::ClosedByPlayer(cPlayer & a_Player, bool a_CanRefuse)
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bool res;
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if (
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m_OnClosing->Call(this, &a_Player, a_CanRefuse, cLuaState::Return, res) && // The callback succeeded
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res // The callback says not to close the window
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res // The callback says not to close the window
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)
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{
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// The callback disagrees (the higher levels check the CanRefuse flag compliance)
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@ -60,7 +60,7 @@ protected:
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/** Contents of the non-inventory part */
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cItemGrid m_Contents;
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/** The Lua state that has opened the window and owns the m_LuaRef */
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/** The canon Lua state that has opened the window and owns the m_LuaRef */
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cLuaState * m_LuaState;
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/** The Lua callback to call when the window is closing for any player */
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