Add-Ons & Services

Poco::Process results in hang after launched process killed

A general discussion forum.
Posts: 89
Joined: 08 Nov 2010, 17:29

Poco::Process results in hang after launched process killed

Postby marlowabnp » 14 Sep 2011, 15:40

A program of mine that uses Poco to launch processes was mysteriously hanging, apparantly randomly. At long last I have been able to reproduce the problem. The code is shown below.

The problem happens if built with or without -g but does not happen when running under the debugger.

I am running on Linux using GCC 4.4.5, using Poco version 1.4.1.

Basically, I create a thread does a launch followed by a wait. In the meantime the main thread kills the pid. This causes the thread to return from the wait but the main thread then hangs on the exit.

struct my_thread
int pid;
boost::thread* the_thread = new boost::thread(&my_thread::run, this);

void run()
std::vector<std::string> no_args;
Poco::ProcessHandle process_handle = Poco::Process::launch("./beta", no_args);
pid = process_handle.id();
int exit_status = process_handle.wait();
std::cout << "run_beta has finished" << std::endl;

int main(int argc, char* argv[])
my_thread t;
std::cout << "kill complete will now exit." << std::endl;
return 0;

This is extremely cut down just to show the problem. My actual app communicates the pid via a concurrent queue object and it cleans up the boost thread object properly, doing the required join. The app is valgrind-clean (i.e no corruption, memory leaks etc). I realise the above app leaks a boost thread and does not synchronise access to the pid properly; that's why the sleep is there. It's a crude kludge to make the app simpler. The "./beta" is it launching a shellscript that goes to sleep for a long time.

An interesting point is that when I replace ./beta with sleep (adjusting the arg vector to specify a large sleep value) the problem mysteriously goes away. So maybe it is somehow connected to launching processes that are shellscripts.


Andrew Marlow

Return to “General Discussion”

Who is online

Users browsing this forum: No registered users and 1 guest