Assertion `!pthread_mutex_lock(&m)' failed.

(gdb) backtrace
#0  0x00007ffff7101445 in __GI_raise (sig=<optimized out>)
    at ../nptl/sysdeps/unix/sysv/linux/raise.c:64
#1  0x00007ffff7104bab in __GI_abort () at abort.c:91
#2  0x00007ffff70fa10e in __assert_fail_base (fmt=<optimized out>,
    assertion=0x461b97 "!pthread_mutex_lock(&m)",
    file=0x4626b0 "/usr/local/boost_1_50_0/libbin/include/boost/thread/pthread/recursive_mutex.hpp", line=<optimized out>, function=<optimized out>)
    at assert.c:94
#3  0x00007ffff70fa1b2 in __GI___assert_fail (
    assertion=0x461b97 "!pthread_mutex_lock(&m)",
    file=0x4626b0 "/usr/local/boost_1_50_0/libbin/include/boost/thread/pthread/recursive_mutex.hpp", line=105,
    function=0x464b00 "void boost::recursive_mutex::lock()") at assert.c:103
#4  0x000000000040bcc8 in boost::recursive_mutex::lock() [clone .part.99] ()
#5  0x0000000000429a88 in websocketpp::role::server<websocketpp::endpoint<websocketpp::role::server, websocketpp::socket::plain, websocketpp::log::logger> >::listen(boost::asio::ip::basic_endpoint<boost::asio::ip::tcp> const&, unsigned long) ()
#6  0x0000000000429d6f in websocketpp::role::server<websocketpp::endpoint<websocketpp::role::server, websocketpp::socket::plain, websocketpp::log::logger> >::listen(unsigned short, unsigned long) ()
#7  0x000000000043af38 in thread_proxy ()
#8  0x00007ffff79a5e9a in start_thread (arg=0x7ffff6dd0700)
    at pthread_create.c:308
#9  0x00007ffff71bd4bd in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112
#10 0x0000000000000000 in ?? ()