path: root/src/cancel.cpp

/*
--
-- 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
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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THE SOFTWARE.

===============================================================================
]]--
*/
#include "_pch.h"
#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_tostring(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;
}