freebsd-skq/share/man/man3/pthread_condattr.3

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.Dd May 9, 2010
.Dt PTHREAD_CONDATTR 3
.Os
.Sh NAME
.Nm pthread_condattr_init ,
.Nm pthread_condattr_destroy ,
.Nm pthread_condattr_getclock ,
.Nm pthread_condattr_setclock ,
.Nm pthread_condattr_getpshared ,
.Nm pthread_condattr_setpshared
.Nd condition attribute operations
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_condattr_init "pthread_condattr_t *attr"
.Ft int
.Fn pthread_condattr_destroy "pthread_condattr_t *attr"
.Ft int
.Fn pthread_condattr_getclock "pthread_condattr_t * restrict attr" "clock_t * restrict clock_id"
.Ft int
.Fn pthread_condattr_setclock "pthread_condattr_t *attr" "clock_t clock_id"
.Ft int
.Fn pthread_condattr_getpshared "pthread_condattr_t * restrict attr" "int * restrict pshared"
.Ft int
.Fn pthread_condattr_setpshared "pthread_condattr_t *attr" "int pshared"
.Sh DESCRIPTION
Condition attribute objects are used to specify parameters to
.Fn pthread_cond_init .
.Pp
The
.Fn pthread_condattr_init
function initializes a condition attribute object with the default attributes.
.Pp
The
.Fn pthread_condattr_destroy
function destroys a condition attribute object.
.Pp
The
.Fn pthread_condattr_getclock
function will put the value of the clock attribute from
.Fa attr
into the memory area pointed to by
.Fa clock_id .
The
.Fn pthread_condattr_setclock
function will set the clock attribute of
.Fa attr
to the value specified in
.Fa clock_id .
The clock attribute affects the interpretation of
.Fa abstime
in
.Xr pthread_cond_timedwait 3
and may be set to
.Dv CLOCK_REALTIME
(default)
or
.Dv CLOCK_MONOTONIC .
.Pp
The
.Fn pthread_condattr_getpshared
function will put the value of the process-shared attribute from
.Fa attr
into the memory area pointed to by
.Fa pshared .
The
.Fn pthread_condattr_setpshared
function will set the process-shared attribute of
.Fa attr
to the value specified in
.Fa pshared .
The argument
.Fa pshared
may have one of the following values:
.Bl -tag -width ".Dv PTHREAD_PROCESS_PRIVATE"
.It Dv PTHREAD_PROCESS_PRIVATE
The condition variable it is attached to may only be accessed by
threads in the same process as the one that created the object.
.It Dv PTHREAD_PROCESS_SHARED
The condition variable it is attached to may be accessed by
threads in processes other than the one that created the object.
.El
.Sh RETURN VALUES
If successful, these functions return 0.
Otherwise, an error number is returned to indicate the error.
.Sh ERRORS
The
.Fn pthread_condattr_init
function will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
Out of memory.
.El
.Pp
The
.Fn pthread_condattr_destroy
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
Invalid value for
.Fa attr .
.El
.Pp
The
.Fn pthread_condattr_setclock
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified in
.Fa clock_id
is not one of the allowed values.
.El
.Pp
The
.Fn pthread_condattr_setpshared
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The value specified in
.Fa pshared
is not one of the allowed values.
.El
.Sh SEE ALSO
.Xr pthread_cond_init 3 ,
.Xr pthread_cond_timedwait 3
.Sh STANDARDS
The
.Fn pthread_condattr_init
and
.Fn pthread_condattr_destroy
functions conform to
.St -p1003.1-96
.Sh BUGS
The implementation of
condition variables
does not fully conform to
.St -p1003.2
because the process-shared attribute is ignored;
if any value other than
.Dv PTHREAD_PROCESSES_PRIVATE
is specified in a call to
.Fn pthread_condattr_setpshared ,
it will return
.Er EINVAL .