NAME
pthread_attr_setprio - Changes the scheduling priority attribute of
thread creation
SYNOPSIS
#include <pthread.h>
int pthread_attr_setprio( pthread_attr_t *attr,
int priority );
PARAMETERS
attr Thread attributes object modified.
priority New value for the priority attribute. The
priority attribute depends on scheduling
policy. Valid values fall within one of the
following ranges:
o PRI_OTHER_MIN <= priority <= PRI_OTHER_MAX
(use with the SCHED_OTHER policy)
o PRI_FIFO_MIN <= priority <= PRI_FIFO_MAX
(use with the SCHED_FIFO policy)
o PRI_RR_MIN <= priority <= PRI_RR_MAX
(use with the SCHED_RR policy)
o PRI_FG_MIN_NP <= priority <= PRI_FG_MAX_NP
(use with the SCHED_FG_NP policy)
o PRI_BG_MIN_NP <= priority <= PRI_BG_MAX_NP
(use with the SCHED_BG_NP policy)
The default priority is the midpoint between PRI_OTHER_MIN and
PRI_OTHER_MAX. To specify a minimum or maximum priority, use the
appropriate symbol; for example, PRI_FIFO_MIN or PRI_FIFO_MAX. To
specify a value between the minimum and maximum, use an appropriate
arithmetic expression. For example, to specify a priority midway
between the minimum and maximum for the Round Robin scheduling policy,
specify the following concept using your programming language's syntax:
pri_rr_mid = (PRI_RR_MIN + PRI_RR_MAX)/2
If your expression results in a value outside the range of minimum to
maximum, an error results when you attempt to use it.
DESCRIPTION
The pthread_attr_setprio() routine sets the execution priority of
threads that are created using the attributes object specified by the
attr parameter.
By default, a created thread inherits the priority of the thread calling
pthread_create(). To specify a priority using this routine, scheduling
inheritance must be disabled at the time the thread is created. Before
calling this routine and pthread_create(), call
pthread_attr_setinheritsched() and specify the value
PTHREAD_DEFAULT_SCHED for the inherit parameter.
An application specifies priority only to express the urgency of execut-
ing the thread relative to other threads. Priority is not used to con-
trol mutual exclusion when accessing shared data.
RETURN VALUES
If the function fails, errno may be set to one of the following values:
Return Error Description
___________________________________________________________
0 Successful completion.
-1 [EINVAL] The value specified by attr is invalid.
-1 [ERANGE] One or more parameters supplied have an
invalid value.
-1 [EPERM] The caller does not have the appropriate
privileges to set the priority of the
specified thread.
RELATED INFORMATION
FUNCTIONS: pthread_attr_create
pthread_attr_getprio
pthread_attr_setinheritsched
pthread_create