【高级技巧】互斥标记：同一资源的重入锁设计

local locks = {}
local function acquire(key, owner)
    local lock = locks[key]
    if lock ~= nil and lock.owner ~= owner then
        return false, lock.owner
    end
    locks[key] = { owner = owner, at = os.time() }
    return true
end
local function release(key, owner)
    local lock = locks[key]
    if lock ~= nil and lock.owner == owner then
        locks[key] = nil
        return true
    end
    return false
end

local function listItem(actor, stallId, itemName, price)
    actor = getplayerbyname(actor)
    local ok, holder = acquire("stall_" .. stallId, tostring(actor))
    if not ok then
        sendmsg(actor, 1, "摊位正被 " .. holder .. " 操作，请稍后再试。")
        return
    end
    setplayvar(actor, "HUMAN", "Stall_" .. stallId, itemName .. "|" .. price, 1)
    release("stall_" .. stallId, tostring(actor))
    sendmsg(actor, 1, "摊位挂单成功：" .. itemName)
end