I have met this froze several times, cpu usage is 100%, here is some info from gdb
(gdb) bt
#0 0x0000000000dcecf5 in void fc::divide<fc::uint128>(fc::uint128 const&, fc::uint128 const&, fc::uint128&, fc::uint128&) ()
#1 0x0000000000dcedf4 in fc::uint128::operator/=(fc::uint128 const&) ()
#2 0x0000000000be6d9a in graphene::chain::database::clear_expired_orders() ()
#3 0x0000000000beda0f in graphene::chain::database::_apply_block(graphene::chain::signed_block const&) ()
#4 0x0000000000bee835 in graphene::chain::database::apply_block(graphene::chain::signed_block const&, unsigned int) ()
#5 0x0000000000beed34 in graphene::chain::database::_push_block(graphene::chain::signed_block const&) ()
#6 0x0000000000bf0af3 in graphene::chain::database::push_block(graphene::chain::signed_block const&, unsigned int) ()
#7 0x0000000000a3783d in graphene::app::detail::application_impl::handle_block(graphene::net::block_message const&, bool, std::vector<fc::ripemd160, std::allocator<fc::ripemd160> >&) ()
#8 0x0000000000f3f9d7 in fc::detail::functor_run<graphene::net::detail::statistics_gathering_node_delegate_wrapper::handle_block(graphene::net::block_message const&, bool, std::vector<fc::ripemd160, std::allocator<fc::ripemd160> >&)::{lambda()#1}>::run(void*, fc::detail::functor_run<graphene::net::detail::statistics_gathering_node_delegate_wrapper::handle_block(graphene::net::block_message const&, bool, std::vector<fc::ripemd160, std::allocator<fc::ripemd160> >&)::{lambda()#1}>) ()
#9 0x0000000000dedfa4 in fc::task_base::run_impl() ()
#10 0x0000000000debbaf in fc::thread_d::process_tasks() ()
#11 0x0000000000debdf1 in fc::thread_d::start_process_tasks(long) ()
#12 0x0000000001061621 in make_fcontext ()
#13 0x0000000000000000 in ?? ()
seems froze at here
285 // At each iteration, we either consume the current order and remove it, or we move to the next asset
286 for( auto itr = settlement_index.lower_bound(current_asset);
287 itr != settlement_index.end();
288 itr = settlement_index.lower_bound(current_asset) )
289 {
290 const force_settlement_object& order = *itr;
291 auto order_id = order.id;
292 current_asset = order.settlement_asset_id();
293 const asset_object& mia_object = get(current_asset);
294 const asset_bitasset_data_object mia = mia_object.bitasset_data(*this);
295
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