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$FreeBSD: src/lib/libpthread/man/pthread_mutexattr.3,v 1.8 2002/09/16 19:29:29 mini Exp $
.Dd July 9, 2010 .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 .Nd mutex attribute operations .Sh LIBRARY .Lb libpthread .Sh SYNOPSIS n 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" .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.
p The .Fn pthread_mutexattr_init function initializes .Fa attr with all the default mutex attributes.
p The .Fn pthread_mutexattr_destroy function destroys .Fa attr .
p The .Fn pthread_mutexattr_settype functions set the mutex .Fa type value of the attribute. Valid mutex types are: l -tag -width "XXX" -offset 2n t 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. t 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. t 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.
p 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 . t 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.
p This is the default mutex type for .Fn pthread_mutexaddr_init . .El
p The .Fn pthread_mutexattr_gettype functions copy the type value of the attribute to the location pointed to by the second parameter. .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: l -tag -width Er t Bq Er ENOMEM Insufficient memory exists to initialize the mutex attributes object. .El
p The .Fn pthread_mutexattr_settype function shall fail if: l -tag -width Er t Bq Er EINVAL The value specified either by .Fa type or .Fa attr is invalid. .El
p
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
.Sh SEE ALSO
.Xr pthread_mutex_init 3
.Sh STANDARDS
These functions conform to
.St -p1003.1-2001 .