Re: [boost] asio::ip::tcp::socket and boost::thread

Subject: Re: [boost] asio::ip::tcp::socket and boost::thread
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2010-01-06 12:46:56

xutm wrote:
> If i want to kill a thread which is no longer useful,
> I think i just need to call the two lines: " thrd->interrupt();" and "
> thrd->detach();" . But actully, the two lines cannot kill the thread.

POSIX defines a thread cancellation scheme in which a thread that is 
blocked doing i/o can be killed, however nether Boost.Thread nor the 
forthcoming C++0x std::thread allow this.  If you are running on a 
POSIX platform you can avoid those C++ thread libraries and manage 
threads directly via the POSIX API, but in that case you have the 
question of how cleanly the killed thread will terminate i.e. will it 
call destructors.  In general it will not do so, but GNU libc does call 
destructors in this case.  So you can get the behaviour that you want 
if you are running on a GNU libc platform and if you're prepared to 
write your own thread class.  Otherwise, threads that are blocking 
doing i/o are unkillable.

One work-around is to have a single thread doing all i/o using e.g. 
select() to avoid blocking, and transfering data to and from the other 
threads using condition variables.  Those threads will block waiting on 
the condition variables, and that blocking is interruptable with 
Boost.Thread.  (I don't know much about Boost.asio, but I would guess 
that it has support for this sort of thing.)  Or, just don't use threads.

Regards,  Phil.