NetBSD/lib/libpthread/pthread_mutexattr.3

.\" $NetBSD: pthread_mutexattr.3,v 1.7 2007/04/17 21:11:47 heinz Exp $
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.\" Copyright (C) 2000 Jason Evans <jasone@FreeBSD.org>.
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.\" $FreeBSD: src/lib/libpthread/man/pthread_mutexattr.3,v 1.8 2002/09/16 19:29:29 mini Exp $
.Dd January 30, 2003
.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
.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"
.Sh DESCRIPTION
Mutex attributes are used to specify parameters to
.Fn pthread_mutex_init .
One attribute object can be used in multiple calls to
.Fn pthread_mutex_init ,
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 type value of the attribute.
Valid mutex types are:
.Dv PTHREAD_MUTEX_NORMAL ,
.Dv PTHREAD_MUTEX_ERRORCHECK ,
.Dv PTHREAD_MUTEX_RECURSIVE ,
and
.Dv PTHREAD_MUTEX_DEFAULT .
The default mutex type for
.Fn pthread_mutexaddr_init
is
.Dv PTHREAD_MUTEX_DEFAULT .
.Pp
.Dv PTHREAD_MUTEX_NORMAL
mutexes do not check for usage errors.
.Dv PTHREAD_MUTEX_NORMAL
mutexes 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.
.Pp
.Dv PTHREAD_MUTEX_ERRORCHECK
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.
.Pp
.Dv PTHREAD_MUTEX_RECURSIVE
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
.Dv PTHREAD_MUTEX_DEFAULT
mutexes result in 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
.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
.Fn pthread_mutexattr_init
shall fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
Insufficient memory exists to initialize the mutex attributes object.
.El
.Pp
.Fn pthread_mutexattr_settype
shall fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified by
.Fa type
is invalid.
.El
.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
.Pp
.Fn pthread_mutexattr_destroy ,
.Fn pthread_mutexattr_settype ,
and
.Fn pthread_mutexattr_gettype
may fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Sh SEE ALSO
.Xr pthread_mutex_init 3
.Sh STANDARDS
.Fn pthread_mutexattr_init ,
.Fn pthread_mutexattr_destroy ,
.Fn pthread_mutexattr_settype ,
.\" .Fn pthread_mutexattr_setprioceiling ,
.\" .Fn pthread_mutexattr_getprioceiling ,
.\" .Fn pthread_mutexattr_setprotocol ,
.\" .Fn pthread_mutexattr_getprotocol ,
and
.Fn pthread_mutexattr_gettype
conform to
.St -p1003.1-96 .