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.TH PTHREAD_MUTEXATTR_GETPRIOCEILING 3C "Apr 1, 2008"
.SH NAME
pthread_mutexattr_getprioceiling, pthread_mutexattr_setprioceiling \- get or
set prioceiling attribute of mutex attribute object
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_mutexattr_getprioceiling\fR(
     \fBconst pthread_mutexattr_t *restrict\fR \fIattr\fR,
     \fBint *restrict\fR \fIprioceiling\fR);
.fi

.LP
.nf
\fBint\fR \fBpthread_mutexattr_setprioceiling\fR(\fBpthread_mutexattr_t *\fR\fIattr\fR,
     \fBint\fR \fIprioceiling\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBpthread_mutexattr_getprioceiling()\fR and
\fBpthread_mutexattr_setprioceiling()\fR functions, respectively, get and set
the priority ceiling attribute of a mutex attribute object pointed to by
\fIattr\fR, which was previously created by the \fBpthread_mutexattr_init()\fR
function.
.sp
.LP
The \fIprioceiling\fR attribute contains the priority ceiling of initialized
mutexes. The values of \fIprioceiling\fR must be within the range of priorities
defined by \fBSCHED_FIFO\fR.
.sp
.LP
The \fIprioceiling\fR 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 must be set to a priority higher than or equal to
the highest priority of all the threads that may lock that mutex.
.sp
.LP
The ceiling value should be drawn from the range of priorities for the
\fBSCHED_FIFO\fR 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 (\fBSCHED_FIFO\fR, in this case).    If a thread changes its scheduling
policy while holding a ceiling mutex, the  behavior of
\fBpthread_mutex_lock()\fR and \fBpthread_mutex_unlock()\fR on this mutex is
undefined. See \fBpthread_mutex_lock\fR(3C).
.SH RETURN VALUES
.sp
.LP
Upon successful completion, the \fBpthread_mutexattr_getprioceiling()\fR and
\fBpthread_mutexattr_setprioceiling()\fR functions return  \fB0\fR. Otherwise,
an error number is returned to indicate the error.
.SH ERRORS
.sp
.LP
The \fBpthread_mutexattr_setprioceiling()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value specified by \fIattr\fR is \fINULL\fR or \fIprioceiling\fR is
invalid.
.RE

.sp
.LP
The \fBpthread_mutexattr_getprioceiling()\fR and
\fBpthread_mutexattr_setprioceiling()\fR functions may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value specified by \fIattr\fR or \fIprioceiling\fR is invalid.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
The caller does not have the privilege to perform the operation.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Committed
_
MT-Level	MT-Safe
_
Standard	See \fBstandards\fR(7).
.TE

.SH SEE ALSO
.sp
.LP
.BR pthread_cond_init (3C),
.BR pthread_create (3C),
.BR pthread_mutex_init (3C),
.BR pthread_mutex_lock (3C),
.BR sched_get_priority_min (3C),
.BR attributes (7),
.BR standards (7)