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.Dd November 31, 2017
.Dt PTHREAD_MUTEX_GETPRIOCEILING 3
.Os
.Sh NAME
.Nm pthread_mutex_getprioceiling ,
.Nm pthread_mutex_setprioceiling
.Nd get or set the priority ceiling of a mutex
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_mutex_getprioceiling "const pthread_mutex_t * restrict mutex" "int * restrict prioceiling"
.Ft int
.Fn pthread_mutex_setprioceiling "pthread_mutex_t * restrict mutex" "int prioceiling" "int * restrict old_ceiling"
.Sh DESCRIPTION
The
.Fn pthread_mutex_getprioceiling
function shall return the current priority ceiling of the mutex.
.Pp
The
.Fn pthread_mutex_setprioceiling
function shall either lock the mutex if it is unlocked, or block until
it can successfully lock the mutex, then it shall change the mutex's priority
ceiling and release the mutex.
When the change is successful, the previous value of the priority ceiling
shall be returned
in
.Fa old_ceiling .
The process of locking the mutex need not adhere to the priority
protect protocol.
If the
.Fn pthread_mutex_setprioceiling
function fails, the mutex priority ceiling shall not be changed.
.Sh RETURN VALUES
If successful, these functions return 0.
Otherwise, an error number is returned to indicate the error.
.Sh ERRORS
The
.Fn pthread_mutex_getprioceiling
and
.Fn pthread_mutex_setprioceiling
functions will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The priority requested by
.Fa prioceiling
is out of range; or
the value specified by
.Fa mutex
does not refer to a currently existing mutex.
.It Bq Er EPERM
The caller does not have the privilege to perform the operation.
.El
.Sh SEE ALSO
.Xr pthread_mutex_destroy 3 ,
.Xr pthread_mutex_init 3 ,
.Xr pthread_mutex_lock 3 ,
.Xr pthread_mutex_timedlock 3 ,
.Xr pthread_mutex_trylock 3 ,
.Xr pthread_mutex_unlock 3