Re: [Boost-users] [ASIO] random crashes

Subject: Re: [Boost-users] [ASIO] random crashes
From: Jon Biggar (jon_at_[hidden])
Date: 2009-01-28 12:57:49

Axel wrote:
> 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 ?

 From my experience, this is likely due to trying to invoke a member 
function on a lock that is already destroyed.  You probably have a race 
condition where you are doing something on the ASIO socket after it's 
already been destroyed.

> 
> 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 ?

This is usually caused by a thread that trashes its stack.  That can 
also be caused by accessing an object that is already destroyed.

-- 
Jon Biggar
jon_at_[hidden]
jon_at_[hidden]