Description

   This routine sets the scheduling policy of a thread that is
   created using the attributes object specified by the attr
   argument. The default value of the scheduling attribute is SCHED_
   OTHER.

   By default, a created thread inherits the policy of the thread
   calling pthread_create(). To specify a policy using this routine,
   scheduling inheritance must be disabled at the time the thread
   is created. Before calling pthread_create(), call pthread_attr_
   setinheritsched() and specify the value PTHREAD_EXPLICIT_SCHED
   for the inherit argument.

   Preemption is caused by both scheduling and policy. Never attempt
   to use scheduling as a mechanism for synchronization.