Hello I m using ASIO library (from boost 1.35) in a network daemon (running on a Debian Etch system). The code structure is almost the same as the one described in the HTTP Server example (http://tenermerx.com/Asio/boost_asio_1_3_1/doc/html/boost_asio/examples.html...). One io_service is used, async_accept() creates new "sessions" and so on. The daemon can run flawlessly for weeks (or only some hours), and crash randomly (segmentation fault). The "network" load isn't really high, every 5 minutes, a few megabytes of data (characters) are sent to the daemon. I didn't noticed any memory leaks or null pointers accesses. Among many crashes, I found 2 kind of crashes. Since core are dumped, I tried to debug it, but I don't know how to interpret the core result. The binary wasn't linked against debug libraries and I just can get debug data from the binary itself. Here's the gdb output on "bt full" command. The daemon has 4 threads, here s the gdb output of the one which causes the crash (I assume this is this one) First kind of crash : (only the relevant part is pasted, the output is huge). It seems to be related to the way I handle the timeout on a timer. In my daemon, the io_service thread may call close() function on the socket object when another thread may call cancel() on the socket object. Could this lead to a crash ? (I can post source code if needed) What is the best way to handle receive timeout *and* socket & timer close from another thread ? Thread 1 (process 27120): Program terminated with signal 11, Segmentation fault. #0 0xb7c7c024 in pthread_mutex_lock () from /lib/tls/i686/cmov/libpthread.so.0 No symbol table info available. #1 0xb7d5f0c6 in pthread_mutex_lock () from /lib/tls/i686/cmov/libc.so.6 No symbol table info available. #2 0x08060438 in boost::asio::detail::posix_mutex::lock (this=0x16) at /usr/include/boost/asio/detail/posix_mutex.hpp:71 error = 0 #3 0x08060559 in scoped_lock (this=0xb796807c, m=@0x16) at /usr/include/boost/asio/detail/scoped_lock.hpp:36 No locals. #4 0x08060ad0 in boost::asio::detail::epoll_reactor<false>::close_descriptor (this=0x2, descriptor=-1291829448) at /usr/include/boost/asio/detail/epoll_reactor.hpp:297 lock = {<boost::noncopyable_::noncopyable> = {<No data fields>}, mutex_ = @0x16, locked_ = 212} ev = {events = 6, data = {ptr = 0x25, fd = 37, u32 = 37, u64 = 8589934629}} #5 0x0809b189 in boost::asio::detail::reactive_socket_service<boost::asio::ip::tcp, boost::asio::detail::epoll_reactor<false> >::close (this=0xb3004358, impl=@0xb3037f1c, ec=@0xb7968128) at /usr/include/boost/asio/detail/reactive_socket_service.hpp:210 No locals. #6 0x0809b277 in boost::asio::stream_socket_service<boost::asio::ip::tcp>::close (this=0xb3000098, impl=@0xb3037f1c, ec=@0xb7968128) at /usr/include/boost/asio/stream_socket_service.hpp:145 No locals. #7 0x0809b2c5 in boost::asio::basic_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >::close (this=0xb3037f18) at /usr/include/boost/asio/basic_socket.hpp:253 ec = {m_val = 0, m_cat = 0xb7c74c10} #8 0x08091129 in Session::handleTimeout (this=0xb3037f18, error=@0xb796821c) at Session.cc:80 Could someone bring me some explainations about this crash ? Second kind of crash : (I really have no idea from where could come the crash, the backtrace isn't very useful) (gdb) bt full #0 boost::asio::detail::scoped_lock<boost::asio::detail::posix_mutex>::unlock (this=0xb5631dac) at /usr/include/boost/asio/detail/scoped_lock.hpp:58 No locals. #1 0x00000000 in ?? () No symbol table info available. Could someone give me some advices about how to handle these crashes ? How could I get more data in backtrace ? Thanks in advance for your help. Regards