Deadlock when spawning threads?

Question

I have an application that has one main thread which spawns another thread which spawns threads for each request received and I'm getting a core dump probably due to a deadlock. On gdb I see the following:

__lll_lock_wait_private ();
_L_lock_4714 ();
start_thread ();
clone ();

This is generated from the following code sample:

do 
{
    pthread_t handle;
    pthread_attr_t attr;
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
    pthread_create(&handle, 0, run, msg);
    pthread_detach(handle);
} while (!stop)

run is an extern function while the rest of the code is part of class methods.

void* run(void* arg)
{
    Handler handler;
    Msg* msg = static_cast<Msg*> (arg);

    handler.handleMsg(msg);

    return NULL;
}

handleMsg method does some processing and then call another application thru a system call:

...
system("AnotherApplication param1, param2 &");
...

Note the ampersand. It is on purpose because I want the process to run asynchronously. The response goes thru the main thread thru another type of communication.

This application has been running on Linux:

Linux 2.6.32-358.14.1.el6.x86_64 #1 SMP Mon Jun 17 15:54:20 EDT 2013 x86_64 x86_64 x86_64 GNU/Linux

I'm not ignoring any signals.

What could be the problem here?

Is that literally your thread-start loop? Spin up as many as possible, as fast as possible, until a local variable becomes true (which it may never)? — WhozCraig
Do you check the return codes of any of these calls and respond or log them somewhere? — Duck

oakad oakad · Accepted Answer · 2013-12-11T00:19:59

pthread_detach manual informs us:

Attempting to detach an already detached thread results in unspecified behavior.

However, you're creating your threads as detached from the start up.

What results do you expect?

Deadlock when spawning threads?

1 Answers