The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> pthread_mutexattr_getprioceiling, pthread_mutexattr_setprioceiling - get and set the prioceiling attribute of the mutex attributes object (REALTIME THREADS)

#### SYNOPSIS

> ``[RPP|TPP] #include <pthread.h>
> int pthread_mutexattr_getprioceiling(const pthread_mutexattr_t
> *restrict` attr`, int *restrict` prioceiling`);
> int pthread_mutexattr_setprioceiling(pthread_mutexattr_t *`attr`,
> int` prioceiling`);``
> `
> `

#### DESCRIPTION

> The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions, respectively, shall get and set the priority ceiling attribute of a mutex attributes object pointed to by attr which was previously created by the function pthread_mutexattr_init().

> The prioceiling attribute contains the priority ceiling of initialized mutexes. The values of prioceiling are within the maximum range of priorities defined by SCHED_FIFO.

> The prioceiling attribute defines the priority ceiling of initialized mutexes, which is the minimum priority level at which the critical section guarded by the mutex is executed. In order to avoid priority inversion, the priority ceiling of the mutex shall be set to a priority higher than or equal to the highest priority of all the threads that may lock that mutex. The values of prioceiling are within the maximum range of priorities defined under the SCHED_FIFO scheduling policy.

> The behavior is undefined if the value specified by the attr argument to pthread_mutexattr_getprioceiling() or pthread_mutexattr_setprioceiling() does not refer to an initialized mutex attributes object.

#### RETURN VALUE

> Upon successful completion, the pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions shall return zero; otherwise, an error number shall be returned to indicate the error.

#### ERRORS

> These functions may fail if:

> [EINVAL]
>   The value specified by prioceiling is invalid.
> [EPERM]
>   The caller does not have the privilege to perform the operation.

> These functions shall not return an error code of [EINTR].

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> None.

#### RATIONALE

> If an implementation detects that the value specified by the attr argument to pthread_mutexattr_getprioceiling() or pthread_mutexattr_setprioceiling() does not refer to an initialized mutex attributes object, it is recommended that the function should fail and report an [EINVAL] error.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> pthread_cond_destroy, pthread_create, pthread_mutex_destroy

> XBD <pthread.h>

#### CHANGE HISTORY

> First released in Issue 5. Included for alignment with the POSIX Threads Extension.

> Marked as part of the Realtime Threads Feature Group.

#### Issue 6

> The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions are marked as part of the Threads and Thread Priority Protection options.

> The [ENOSYS] error condition has been removed as stubs need not be provided if an implementation does not support the Thread Priority Protection option.

> The [ENOTSUP] error condition has been removed since these functions do not have a protocol argument.

> The restrict keyword is added to the pthread_mutexattr_getprioceiling() prototype for alignment with the ISO/IEC 9899:1999 standard.

#### Issue 7

> The pthread_mutexattr_getprioceiling() and pthread_mutexattr_setprioceiling() functions are moved from the Threads option to require support of either the Robust Mutex Priority Protection option or the Non-Robust Mutex Priority Protection option.

> The [EINVAL] error for an uninitialized mutex attributes object is removed; this condition results in undefined behavior.

End of informative text.

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