C++ pthread 02

Table of contents

void *thread_callback( void *heap_argument )
{
  // cancelation is define inside the thread
  // it cannot be assigned to another thread
  pthread_setcancelstate( PTHREAD_CANCEL_ENABLE, 0 );
  pthread_setcanceltype( PTHREAD_CANCEL_ASYNCHRONOUS, 0 );

  int local_argument = *(int *)heap_argument;
  free( heap_argument );
  while( 1 ) {
    printf( "thread %d\n", local_argument );
    sleep( 1 );
  }

  printf( "This line should never be reached\n" );
  return 0;
}

void create_a_cancelable_thread( pthread_t *thread_handler, int local_argument )
{
  pthread_attr_t attr;
  pthread_attr_init( &attr );
  pthread_attr_setdetachstate( &attr, PTHREAD_CREATE_JOINABLE );

  // Allocate memory for the arguments
  int *heap_argument = (int *)calloc( 1, sizeof( int ) );
  *heap_argument     = local_argument;

  // POSIX thread creation
  pthread_create( thread_handler, &attr, &thread_callback, (void *)heap_argument );
}

void cancel_thread( pthread_t thread_handler, int tid )
{
  // Cancelation is async, then it does not occurs on the exact time of cancel is called
  printf( "Canceling thread #%d\n", tid );
  pthread_cancel( thread_handler );
}

int main( [[maybe_unused]] int argc, [[maybe_unused]] char **argv )
{
  pthread_t t1;
  pthread_t t2;
  pthread_t t3;
  create_a_cancelable_thread( &t1, 1 );
  create_a_cancelable_thread( &t2, 2 );
  create_a_cancelable_thread( &t3, 3 );
  sleep( 2 );
  cancel_thread( t1, 1 );
  sleep( 2 );
  cancel_thread( t2, 2 );
  sleep( 2 );
  cancel_thread( t3, 3 );
  sleep( 1 );
  return 0;
}

Possible output

thread 1
thread 2
thread 3
thread 1
thread 3
thread 2
Canceling thread #1
thread 1
thread 3
thread 2
thread 3
thread 2
thread 3
thread 2
Canceling thread #2
thread 3
thread 3
Canceling thread #3

References

• Udemy Understanding Thread Cancellation - Asynchronous Mode