/*
--
-- CANCEL.CPP
--
-- Lane cancellation support
--
-- Author: Benoit Germain <bnt.germain@gmail.com>
--
--[[
===============================================================================
Copyright (C) 2011-2024 Benoit Germain <bnt.germain@gmail.com>
Permission is hereby granted, free of charge, to any person obtaining a copy
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The above copyright notice and this permission notice shall be included in
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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THE SOFTWARE.
===============================================================================
]]--
*/
#include "cancel.h"
#include "debugspew.h"
#include "lane.h"
// #################################################################################################
// #################################################################################################
/*
* Check if the thread in question ('L') has been signalled for cancel.
*
* Called by cancellation hooks and/or pending Linda operations (because then
* the check won't affect performance).
*
* Returns CANCEL_SOFT/HARD if any locks are to be exited, and 'raise_cancel_error()' called,
* to make execution of the lane end.
*/
[[nodiscard]] static inline CancelRequest cancel_test(lua_State* L_)
{
Lane* const _lane{ kLanePointerRegKey.readLightUserDataValue<Lane>(L_) };
// 'lane' is nullptr for the original main state (and no-one can cancel that)
return _lane ? _lane->cancelRequest : CancelRequest::None;
}
// #################################################################################################
//---
// bool = cancel_test()
//
// Available inside the global namespace of lanes
// returns a boolean saying if a cancel request is pending
//
LUAG_FUNC(cancel_test)
{
CancelRequest _test{ cancel_test(L_) };
lua_pushboolean(L_, _test != CancelRequest::None);
return 1;
}
// #################################################################################################
// #################################################################################################
[[nodiscard]] static void cancel_hook(lua_State* L_, [[maybe_unused]] lua_Debug* ar_)
{
DEBUGSPEW_CODE(DebugSpew(nullptr) << "cancel_hook" << std::endl);
if (cancel_test(L_) != CancelRequest::None) {
lua_sethook(L_, nullptr, 0, 0);
raise_cancel_error(L_);
}
}
// #################################################################################################
// #################################################################################################
//---
// = thread_cancel( lane_ud [,timeout_secs=0.0] [,wake_lindas_bool=false] )
//
// The originator thread asking us specifically to cancel the other thread.
//
// 'timeout': <0: wait forever, until the lane is finished
// 0.0: just signal it to cancel, no time waited
// >0: time to wait for the lane to detect cancellation
//
// 'wake_lindas_bool': if true, signal any linda the thread is waiting on
// instead of waiting for its timeout (if any)
//
// Returns: true if the lane was already finished (Done/Error/Cancelled) or if we
// managed to cancel it.
// false if the cancellation timed out, or a kill was needed.
//
// #################################################################################################
[[nodiscard]] static CancelResult thread_cancel_soft(Lane* lane_, std::chrono::time_point<std::chrono::steady_clock> until_, bool wakeLane_)
{
lane_->cancelRequest = CancelRequest::Soft; // it's now signaled to stop
// negative timeout: we don't want to truly abort the lane, we just want it to react to cancel_test() on its own
if (wakeLane_) { // wake the thread so that execution returns from any pending linda operation if desired
std::condition_variable* const _waiting_on{ lane_->waiting_on };
if (lane_->status == Lane::Waiting && _waiting_on != nullptr) {
_waiting_on->notify_all();
}
}
return lane_->waitForCompletion(until_) ? CancelResult::Cancelled : CancelResult::Timeout;
}
// #################################################################################################
[[nodiscard]] static CancelResult thread_cancel_hard(Lane* lane_, std::chrono::time_point<std::chrono::steady_clock> until_, bool wakeLane_)
{
lane_->cancelRequest = CancelRequest::Hard; // it's now signaled to stop
// lane_->thread.get_stop_source().request_stop();
if (wakeLane_) { // wake the thread so that execution returns from any pending linda operation if desired
std::condition_variable* const _waiting_on{ lane_->waiting_on };
if (lane_->status == Lane::Waiting && _waiting_on != nullptr) {
_waiting_on->notify_all();
}
}
CancelResult result{ lane_->waitForCompletion(until_) ? CancelResult::Cancelled : CancelResult::Timeout };
return result;
}
// #################################################################################################
CancelResult thread_cancel(Lane* lane_, CancelOp op_, int hookCount_, std::chrono::time_point<std::chrono::steady_clock> until_, bool wakeLane_)
{
// remember that lanes are not transferable: only one thread can cancel a lane, so no multithreading issue here
// We can read 'lane_->status' without locks, but not wait for it (if Posix no PTHREAD_TIMEDJOIN)
if (lane_->status >= Lane::Done) {
// say "ok" by default, including when lane is already done
return CancelResult::Cancelled;
}
// signal the linda the wake up the thread so that it can react to the cancel query
// let us hope we never land here with a pointer on a linda that has been destroyed...
if (op_ == CancelOp::Soft) {
return thread_cancel_soft(lane_, until_, wakeLane_);
} else if (static_cast<int>(op_) > static_cast<int>(CancelOp::Soft)) {
lua_sethook(lane_->L, cancel_hook, static_cast<int>(op_), hookCount_);
}
return thread_cancel_hard(lane_, until_, wakeLane_);
}
// #################################################################################################
// #################################################################################################
CancelOp which_cancel_op(std::string_view const& opString_)
{
CancelOp _op{ CancelOp::Invalid };
if (opString_ == "hard") {
_op = CancelOp::Hard;
} else if (opString_ == "soft") {
_op = CancelOp::Soft;
} else if (opString_== "call") {
_op = CancelOp::MaskCall;
} else if (opString_ == "ret") {
_op = CancelOp::MaskRet;
} else if (opString_ == "line") {
_op = CancelOp::MaskLine;
} else if (opString_ == "count") {
_op = CancelOp::MaskCount;
}
return _op;
}
// #################################################################################################
[[nodiscard]] static CancelOp which_cancel_op(lua_State* L_, int idx_)
{
if (luaG_type(L_, idx_) == LuaType::STRING) {
std::string_view const _str{ luaG_tostringview(L_, idx_) };
CancelOp _op{ which_cancel_op(_str) };
lua_remove(L_, idx_); // argument is processed, remove it
if (_op == CancelOp::Invalid) {
raise_luaL_error(L_, "invalid hook option %s", _str);
}
return _op;
}
return CancelOp::Hard;
}
// #################################################################################################
// bool[,reason] = lane_h:cancel( [mode, hookcount] [, timeout] [, wake_lane])
LUAG_FUNC(thread_cancel)
{
Lane* const _lane{ ToLane(L_, 1) };
CancelOp const _op{ which_cancel_op(L_, 2) }; // this removes the op string from the stack
int _hook_count{ 0 };
if (static_cast<int>(_op) > static_cast<int>(CancelOp::Soft)) { // hook is requested
_hook_count = static_cast<int>(luaL_checkinteger(L_, 2));
lua_remove(L_, 2); // argument is processed, remove it
if (_hook_count < 1) {
raise_luaL_error(L_, "hook count cannot be < 1");
}
}
std::chrono::time_point<std::chrono::steady_clock> _until{ std::chrono::time_point<std::chrono::steady_clock>::max() };
if (luaG_type(L_, 2) == LuaType::NUMBER) { // we don't want to use lua_isnumber() because of autocoercion
lua_Duration const duration{ lua_tonumber(L_, 2) };
if (duration.count() >= 0.0) {
_until = std::chrono::steady_clock::now() + std::chrono::duration_cast<std::chrono::steady_clock::duration>(duration);
} else {
raise_luaL_argerror(L_, 2, "duration cannot be < 0");
}
lua_remove(L_, 2); // argument is processed, remove it
} else if (lua_isnil(L_, 2)) { // alternate explicit "infinite timeout" by passing nil before the key
lua_remove(L_, 2); // argument is processed, remove it
}
// we wake by default in "hard" mode (remember that hook is hard too), but this can be turned off if desired
bool _wake_lane{ _op != CancelOp::Soft };
if (lua_gettop(L_) >= 2) {
if (!lua_isboolean(L_, 2)) {
raise_luaL_error(L_, "wake_lindas parameter is not a boolean");
}
_wake_lane = lua_toboolean(L_, 2);
lua_remove(L_, 2); // argument is processed, remove it
}
STACK_CHECK_START_REL(L_, 0);
switch (thread_cancel(_lane, _op, _hook_count, _until, _wake_lane)) {
default: // should never happen unless we added a case and forgot to handle it
LUA_ASSERT(L_, false);
break;
case CancelResult::Timeout:
lua_pushboolean(L_, 0); // false
lua_pushstring(L_, "timeout"); // false "timeout"
break;
case CancelResult::Cancelled:
lua_pushboolean(L_, 1); // true
std::ignore = _lane->pushThreadStatus(L_); // true status
break;
}
STACK_CHECK(L_, 2);
return 2;
}