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# Execution Scheduling [POSIX Section 13]

## Functions Implemented

    int sched_yield(void);
    int sched_get_priority_max(int policy);
    int sched_get_priority_min(int policy);
    int sched_rr_get_interval(pid_t pid, struct timespec *t);
    int pthread_attr_setscope(pthread_attr_t *attr, int scope);
    int pthread_attr_getscope(const pthread_attr_t *attr, int *scope);
    int pthread_attr_setinheritsched(pthread_attr_t *attr, int inherit);
    int pthread_attr_getinheritsched(const pthread_attr_t *attr, int *inherit);
    int pthread_attr_setschedpolicy(pthread_attr_t *attr, int policy);
    int pthread_attr_getschedpolicy(const pthread_attr_t *attr, int *policy);
    int pthread_attr_setschedparam( pthread_attr_t *attr, const struct sched_param *param);
    int pthread_attr_getschedparam( const pthread_attr_t *attr,
    	                        struct sched_param *param);
    int pthread_setschedparam(pthread_t thread, int policy,
    	                  const struct sched_param *param);
    int pthread_getschedparam(pthread_t thread, int *policy,
    	                  struct sched_param *param);
    int pthread_mutexattr_setprotocol( pthread_mutexattr_t *attr,
                                       int protocol);
    int pthread_mutexattr_getprotocol( pthread_mutexattr_t *attr,
                                       int *protocol);
    int pthread_mutexattr_setprioceiling( pthread_mutexattr_t *attr,
                                          int prioceiling);
    int pthread_mutexattr_getprioceiling( pthread_mutexattr_t *attr,
    	                              int *prioceiling);
    int pthread_mutex_setprioceiling( pthread_mutex_t *mutex,
    	                          int prioceiling,
    	                          int *old_ceiling);
    int pthread_mutex_getprioceiling( pthread_mutex_t *mutex,
                                      int *prioceiling);

## Functions Omitted

    int sched_setparam(pid_t pid, const struct sched_param *param);
    int sched_getparam(pid_t pid, struct sched_param *param);
    int sched_setscheduler(pid_t pid, int policy,
    	               const struct sched_param *param);
    int sched_getscheduler(pid_t pid);

## Notes

- The functions sched_setparam(), sched_getparam(), sched_setscheduler() and sched_getscheduler() are present but always return an error.

- The scheduler policy SCHED_OTHER is equivalent to SCHED_RR.

- Only PTHREAD_SCOPE_SYSTEM is supported as a contentionscope attribute.

- The default thread scheduling attributes are:

      	  contentionscope          PTHREAD_SCOPE_SYSTEM
      	  inheritsched             PTHREAD_INHERIT_SCHED
      	  schedpolicy              SCHED_OTHER
      	  schedparam.sched	   0

- Mutex priority inversion protection is controlled by a number of kernel configuration options. If CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_INHERIT is defined then {_POSIX_THREAD_PRIO_INHERIT} will be defined and PTHREAD_PRIO_INHERIT may be set as the protocol in a pthread_mutexattr_t object. If CYGSEM_KERNEL_SYNCH_MUTEX_PRIORITY_INVERSION_PROTOCOL_CEILING is defined then {_POSIX_THREAD_PRIO_PROTECT} will be defined and PTHREAD_PRIO_PROTECT may be set as the protocol in a pthread_mutexattr_t object.

- The default attribute values set by pthread_mutexattr_init() is to set the protocol attribute to PTHREAD_PRIO_NONE and the prioceiling attribute to zero.

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