pthread_mutexattr.3   [plain text]

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.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 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 *attr" "int *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.
.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.
This is the default mutex type for
.Fn pthread_mutexaddr_init .
.El
.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
The
.Fn pthread_mutexattr_init
function shall fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
Out of memory.
.El
.Pp
The
.Fn pthread_mutexattr_destroy
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
The
.Fn pthread_mutexattr_setprioceiling
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr ,
or invalid value for
.Fa prioceiling .
.El
.Pp
The
.Fn pthread_mutexattr_getprioceiling
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
The
.Fn pthread_mutexattr_setprotocol
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr ,
or invalid value for
.Fa protocol .
.El
.Pp
The
.Fn pthread_mutexattr_getprotocol
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.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
The
.Fn pthread_mutexattr_gettype
function 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
The
.Fn pthread_mutexattr_init
and
.Fn pthread_mutexattr_destroy
functions conform to
.St -p1003.1-96
.Pp
The
.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
functions conform to
.St -susv2