The “flags” thread attribute

The three functions, pthread_attr_setdetachstate(), pthread_attr_setinheritsched(), and pthread_attr_setscope() determine whether the thread is created “joinable” or “detached,” whether the thread inherits the scheduling attributes of the creating thread or uses the scheduling attributes specified by pthread_attr_setschedparam() and pthread_attr_setschedpolicy(), and finally whether the thread has a scope of “system” or “process.”

To create a “joinable” thread (meaning that another thread can synchronize to its termination via pthread_join()), you'd use:

pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_JOINABLE);

To create one that can't be joined (called a “detached” thread), you'd use:

pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);

If you want the thread to inherit the scheduling attributes of the creating thread (that is, to have the same scheduling policy and the same priority), you'd use:

pthread_attr_setinheritsched (&attr, PTHREAD_INHERIT_SCHED);

To create one that uses the scheduling attributes specified in the attribute structure itself (which you'd set using pthread_attr_setschedparam() and pthread_attr_setschedpolicy()), you'd use:

pthread_attr_setinheritsched (&attr, PTHREAD_EXPLICIT_SCHED);

Finally, you'd never call pthread_attr_setscope(). Why? Because QNX Neutrino supports only “system” scope, and it's the default when you initialize the attribute. (“System” scope means that all threads in the system compete against each other for CPU; the other value, “process,” means that threads compete against each other for CPU within the process, and the kernel schedules the processes.)

If you do insist on calling it, you can call it only as follows:

pthread_attr_setscope (&attr, PTHREAD_SCOPE_SYSTEM);