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[apple/libc.git] / pthreads / pthread_mutexattr.3

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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 SYNOPSIS
.Fd #include <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 *attr" "int *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_MUXEX_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 attemps 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 attemps 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.
.Pp
The
.Fn pthread_mutexattr_set*
functions set the attribute that corresponds to each function name.
.Pp
The
.Fn pthread_mutexattr_get*
functions copy the value of the attribute that corresponds to each function name
to the location pointed to by the second function 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
will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
Out of memory.
.El
.Pp
.Fn pthread_mutexattr_destroy
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
.Fn pthread_mutexattr_setprioceiling
will 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
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
.Fn pthread_mutexattr_setprotocol
will 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
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
.Fn pthread_mutexattr_settype
will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr ,
or invalid value for
.Fa type .
.El
.Pp
.Fn pthread_mutexattr_gettype
will 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
and
.Fn pthread_mutexattr_destroy
conform to
.St -p1003.1-96
.Pp
.Fn pthread_mutexattr_setprioceiling ,
.Fn pthread_mutexattr_getprioceiling ,
.Fn pthread_mutexattr_setprotocol ,
.Fn pthread_mutexattr_getprotocol ,
.Fn pthread_mutexattr_settype ,
and
.Fn pthread_mutexattr_gettype
conform to
.St -susv2