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IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE .\" LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR .\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF .\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR .\" BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, .\" WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE .\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, .\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .\" $FreeBSD: src/lib/libpthread/man/pthread_mutexattr.3,v 1.8 2002/09/16 19:29:29 mini Exp $ .Dd June 12, 2016 .Dt PTHREAD_MUTEXATTR 3 .Os .Sh NAME .Nm pthread_mutexattr_init , .Nm pthread_mutexattr_destroy , .Nm pthread_mutexattr_setprioceiling , .Nm pthread_mutexattr_getprioceiling , .Nm pthread_mutexattr_setprotocol , .Nm pthread_mutexattr_getprotocol , .Nm pthread_mutexattr_settype , .Nm pthread_mutexattr_gettype , .Nm pthread_mutexattr_getpshared , .Nm pthread_mutexattr_setpshared .Nd mutex attribute operations .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS .In pthread.h .Ft int .Fn pthread_mutexattr_init "pthread_mutexattr_t *attr" .Ft int .Fn pthread_mutexattr_destroy "pthread_mutexattr_t *attr" .Ft int .Fn pthread_mutexattr_setprioceiling \ "pthread_mutexattr_t *attr" "int prioceiling" .Ft int .Fn pthread_mutexattr_getprioceiling \ "pthread_mutexattr_t *attr" "int *prioceiling" .Ft int .Fn pthread_mutexattr_setprotocol \ "pthread_mutexattr_t *attr" "int protocol" .Ft int .Fn pthread_mutexattr_getprotocol \ "pthread_mutexattr_t *attr" "int *protocol" .Ft int .Fn pthread_mutexattr_settype "pthread_mutexattr_t *attr" "int type" .Ft int .Fn pthread_mutexattr_gettype \ "pthread_mutexattr_t * restrict attr" "int * restrict type" .Ft int .Fn pthread_mutexattr_getpshared \ "const pthread_mutexattr_t * __restrict attr" "int * __restrict pshared" .Ft int .Fn pthread_mutexattr_setpshared \ "pthread_mutexattr_t * attr" "int pshared" .Sh DESCRIPTION Mutex attributes are used to specify parameters to .Fn pthread_mutex_init . Like with thread attributes, one attribute object can be used in multiple calls to .Xr pthread_mutex_init 3 , with or without modifications between calls. .Pp The .Fn pthread_mutexattr_init function initializes .Fa attr with all the default mutex attributes. .Pp The .Fn pthread_mutexattr_destroy function destroys .Fa attr . .Pp The .Fn pthread_mutexattr_settype functions set the mutex .Fa type value of the attribute. Valid mutex types are: .Bl -tag -width "XXX" -offset 2n .It Dv PTHREAD_MUTEX_NORMAL This type of mutex does not check for usage errors. It will deadlock if reentered, and result in undefined behavior if a locked mutex is unlocked by another thread. Attempts to unlock an already unlocked .Dv PTHREAD_MUTEX_NORMAL mutex will result in undefined behavior. .It Dv PTHREAD_MUTEX_ERRORCHECK These mutexes do check for usage errors. If an attempt is made to relock a .Dv PTHREAD_MUTEX_ERRORCHECK mutex without first dropping the lock, an error will be returned. If a thread attempts to unlock a .Dv PTHREAD_MUTEX_ERRORCHECK mutex that is locked by another thread, an error will be returned. If a thread attempts to unlock a .Dv PTHREAD_MUTEX_ERRORCHECK thread that is unlocked, an error will be returned. .It Dv PTHREAD_MUTEX_RECURSIVE These mutexes allow recursive locking. An attempt to relock a .Dv PTHREAD_MUTEX_RECURSIVE mutex that is already locked by the same thread succeeds. An equivalent number of .Xr pthread_mutex_unlock 3 calls are needed before the mutex will wake another thread waiting on this lock. If a thread attempts to unlock a .Dv PTHREAD_MUTEX_RECURSIVE mutex that is locked by another thread, an error will be returned. If a thread attempts to unlock a .Dv PTHREAD_MUTEX_RECURSIVE thread that is unlocked, an error will be returned. .Pp It is advised that .Dv PTHREAD_MUTEX_RECURSIVE mutexes are not used with condition variables. This is because of the implicit unlocking done by .Xr pthread_cond_wait 3 and .Xr pthread_cond_timedwait 3 . .It Dv PTHREAD_MUTEX_DEFAULT Also this type of mutex will cause undefined behavior if reentered. Unlocking a .Dv PTHREAD_MUTEX_DEFAULT mutex locked by another thread will result in undefined behavior. Attempts to unlock an already unlocked .Dv PTHREAD_MUTEX_DEFAULT mutex will result in undefined behavior. .Pp This is the default mutex type for .Fn pthread_mutexattr_init . .El .Pp The .Fn pthread_mutexattr_gettype functions copy the type value of the attribute to the location pointed to by the second parameter. .Pp The .Fn pthread_mutexattr_getpshared function obtains the value of the process-shared attribute from the attributes object referenced by .Fa attr . .Pp The .Fn pthread_mutexattr_setpshared function is used to set the process-shared attribute in an initialised attributes object referenced by .Fa attr . .Pp The .Fn pthread_mutexattr_getprotocol and .Fn pthread_mutexattr_setprotocol functions shall get and set the protocol attribute of a mutex attributes object pointed to by .Fa attr which was previously created by the function .Fn pthread_mutexattr_init . .Pp The .Fn pthread_mutexattr_getprioceiling and .Fn pthread_mutexattr_setprioceiling functions, shall get and set the priority ceiling attribute of a mutex attributes object pointed to by .Fa attr which was previously created by the function .Fn pthread_mutexattr_init . .Sh RETURN VALUES If successful, these functions return 0. Otherwise, an error number is returned to indicate the error. .Sh ERRORS The .Fn pthread_mutexattr_init function shall fail if: .Bl -tag -width Er .It Bq Er ENOMEM Insufficient memory exists to initialize the mutex attributes object. .El .Pp The .Fn pthread_mutexattr_settype function shall fail if: .Bl -tag -width Er .It Bq Er EINVAL The value specified either by .Fa type or .Fa attr is invalid. .El .Pp No error numbers are defined for the .Fn pthread_mutexattr_destroy and .Fn pthread_mutexattr_gettype functions. .Pp .Fn pthread_mutexattr_setprioceiling may fail if: .Bl -tag -width Er .It Bq Er EINVAL Invalid value for .Fa attr , or invalid value for .Fa prioceiling . .El .Pp .Fn pthread_mutexattr_getprioceiling may fail if: .Bl -tag -width Er .It Bq Er EINVAL Invalid value for .Fa attr . .El .Pp .Fn pthread_mutexattr_setprotocol may fail if: .Bl -tag -width Er .It Bq Er EINVAL Invalid value for .Fa attr , or invalid value for .Fa protocol . .El .Pp .Fn pthread_mutexattr_getprotocol may fail if: .Bl -tag -width Er .It Bq Er EINVAL Invalid value for .Fa attr . .El .Pp .Fn pthread_mutexattr_getpshared and .Fn pthread_mutexattr_setpshared may fail if: .Bl -tag -width Er .It Bq Er EINVAL the value specified by .Fa attr is invalid. .El .Sh SEE ALSO .Xr pthread_mutex_init 3 .Sh STANDARDS These functions conform to .St -p1003.1-2001 . .Sh BUGS The .Fn pthread_mutexattr_getpshared and .Fn pthread_mutexattr_setpshared functions are hidden by default since only thread shared attributes are supported.