Question: I have a C++ program on Linux (CentOS 5.3) spawning multiple threads which are in an infinite loop to perform a job and sleep for certain minutes.
Now I have to cancel the running threads in case a new configuration notification comes in and freshly start new set of threads, for which i have used pthread\_cancel.
What I observed was, the threads were not getting stopped even after receiving cancel indication,even some sleeping threads were coming up after the sleep was completed.

As the behavior was not desired, usage of pthread\_cancel in the mentioned scenario raises question about being good or bad practice. 

Please comment on the pthread\_cancel usage in above mentioned scenario.

Answer: 
You can do the equivalent of the code below.

```
#include <pthread.h>
#include <cxxabi.h>
#include <unistd.h>
...
void *Control(void* pparam)
{
    try
    {
        // do your work here, maybe long loop
    }   
    catch (abi::__forced_unwind&)
    {  // handle pthread_cancel stack unwinding exception
        throw;
    }
    catch (exception &ex) 
    {
        throw ex;
    }
}

int main()
{
    pthread_t tid;
    int rtn;
    rtn = pthread_create( &tid, NULL, Control, NULL );

    usleep(500);
    // some other work here

    rtn = pthtead_cancel( tid );
}

```
I'd use boost::asio.

Something like:

```
struct Wait {
  Wait() : timer_(io_service_), run_(true) {}

  boost::asio::io_service io_service_;
  mutable boost::asio::deadline_timer timer_;
  bool run_;
};

void Wait::doWwork() {
  while (run) {
    boost::system::error_code ec;
    timer_.wait(ec);
    io_service_.run();
    if (ec) {
      if (ec == boost::asio::error::operation_aborted) {
        // cleanup
      } else {
        // Something else, possibly nasty, happened
      }
    }
  }
}

void Wait::halt() {
  run_ = false;
  timer_.cancel();
}

```

Once you've got your head round it, asio is a wonderful tool.