have resolved!
when async_write, I use the same custom memory in two thread.

2010/1/13 victor <victor.boost.program@gmail.com>
I call boost::asio::async_write, finally it call "bool enqueue_operation(Descriptor descriptor, Operation operation)"
 
In this function , there is code as flow:
while (current_op->next_)
      current_op = current_op->next_;
 
My process execute it for ever. Using gdb to attach the prcocess, I find :
68          while (current_op->next_)
(gdb) p current_op
$8 = (class boost::asio::detail::reactor_op_queue<int>::op_base *) 0x93381c8
(gdb) p current_op->next_
$9 = (class boost::asio::detail::reactor_op_queue<int>::op_base *) 0x93381c8
 
current_op and current_op->next_ is the same address.
 
how did it come true? I have no any clue. Anyone can offer some suggestion?