Hi! I have strange crashes of my application that uses async ops in multiple threads. Before I describe my vision of the problem I point the following: 1) I'm aware that shared access to the same socket from multiple threads is unsafe. 2) All operations which my code issues on the same socket are made under mutex. As far as I understand, the following happens: 1) One thread issues scatter-gather boost::asio::async_write() for boost::array<boost::asio::const_buffer, 2> on socket A. 2) Another thread closes socket A after that. 3) Meantime (simultaneously with 2), first buffer write is completed and one of the threads running io_service::run() starts to execute second part of async_write from 1). In this place application segfaults: #0 0x00007fa3a3a2c4eb in boost::asio::detail::epoll_reactor::start_op (this=0x19c3410, op_type=1, descriptor=27, descriptor_data=@0x7f9dfc013260, op=0x7f9dfc2d2130, allow_speculative=true) at boost-1_51/boost/asio/detail/impl/epoll_reactor.ipp:219 #1 0x00007fa3a3a2bf63 in boost::asio::detail::reactive_socket_service_base::start_op (this=0x19c4338, impl=..., op_type=1, op=0x7f9dfc2d2130, is_non_blocking=true, noop=false) at boost-1_51/boost/asio/detail/impl/reactive_socket_service_base.ipp:211 #2 0x00007fa3a3af4ec5 in boost::asio::detail::reactive_socket_service_base::async_send (this=0x19c4338, impl=..., buffers=..., flags=0, handler=...) at boost-1_51/boost/asio/detail/reactive_socket_service_base.hpp:212 #3 0x00007fa3a3af90bf in boost::asio::stream_socket_service<boost::asio::ip::tcp>::async_send (this=0x19c4310, impl=..., buffers=..., flags=0, handler=...) at boost-1_51/boost/asio/stream_socket_service.hpp:298 #4 0x00007fa3a3b05992 in boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp>
::async_write_some (this=0x7f9dfc013250, buffers=..., handler=...) at boost-1_51/boost/asio/basic_stream_socket.hpp:676
because descriptor_data equals null-pointer here. The problem is: second write which is issued internally by boost cannot be protected by the same mutex which is used for protected access to the socket in my code. So, the question is: how can I safely close the socket? -- Max