pthread_mutex_getprioceiling

, pthread_mutex_setprioceiling

- change priority ceiling of a mutex

Synopsis

cc –mt [ flag... ] file... [ library... ]
#include <pthread.h>

int pthread_mutex_getprioceiling(const pthread_mutex_t *restrict mutex,
     int *restrict prioceiling);

int pthread_mutex_setprioceiling(pthread_mutex_t *restrict mutex,
     int prioceiling, int *restrict old_ceiling);

Description

The pthread_mutex_getprioceiling() function returns the current priority ceiling of the mutex.

The pthread_mutex_setprioceiling() function either locks the mutex if it is unlocked, or blocks until it can successfully lock the mutex, then it changes the mutex's priority ceiling and releases the mutex. When the change is successful, the previous value of the priority ceiling is returned in old_ceiling. The process of locking the mutex need not adhere to the priority protect protocol.

If the pthread_mutex_setprioceiling() function fails, the mutex priority ceiling is not changed.

The ceiling value should be drawn from the range of priorities for the SCHED_FIFO policy. When a thread acquires such a mutex, the policy of the thread at mutex acquisition should match that from which the ceiling value was derived (SCHED_FIFO, in this case). If a thread changes its scheduling policy while holding a ceiling mutex, the behavior of pthread_mutex_lock() and pthread_mutex_unlock() on this mutex is undefined. See pthread_mutex_lock(3C).

The ceiling value should not be treated as a persistent value resident in a pthread_mutex_t that is valid across upgrades of Solaris. The semantics of the actual ceiling value are determined by the existing priority range for the SCHED_FIFO policy, as returned by the sched_get_priority_min() and sched_get_priority_max() functions (see sched_get_priority_min(3C)) when called on the version of Solaris on which the ceiling value is being utilized.

Return Values

Upon successful completion, the pthread_mutex_getprioceiling() and pthread_mutex_setprioceiling() functions return 0. Otherwise, an error number is returned to indicate the error.

Errors

The pthread_mutex_getprioceiling() and pthread_mutex_setprioceiling() functions may fail if:

EINVAL

The value specified by mutex does not refer to a currently existing mutex.

The pthread_mutex_setprioceiling() function will fail if:

EINVAL

The mutex was not initialized with its protocol attribute having the value of PTHREAD_PRIO_PROTECT.

EINVAL

The priority requested by prioceiling is out of range.

EPERM

The caller does not have the privilege to perform the operation.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

pthread_mutex_init(3C), pthread_mutex_lock(3C), sched_get_priority_min(3C), attributes(5), standards(5)