pthread_setschedparam

Changes the current scheduling policy and scheduling parameters of a thread.

Syntax

pthread_setschedparam(
                      thread,
                      policy,
                      param );
 



Argument         Data Type               Access

thread           opaque pthread_t        read

policy           integer                 read

param            struct sched_param      read

C Binding

#include 


int
pthread_setschedparam (
         pthread_t   thread,
         int   policy,
         const struct sched_param   *param);

Arguments

thread: Thread whose scheduling policy and parameters are to be changed.
policy: New scheduling policy value for the thread specified in thread. The following are valid values:

   SCHED_BG_NP
   SCHED_FG_NP
   SCHED_FIFO
   SCHED_OTHER
   SCHED_RR

See Section 2.2.3.2 for a description of the scheduling policies.

param: New values of the scheduling parameters associated with the scheduling policy for the thread specified in thread. Valid values for the sched_priority field of struct sched_param depend on the chosen policy and fall within one of the following ranges.

Low High

PRI_FIFO_MIN PRI_FIFO_MAX PRI_RR_MIN PRI_RR_MAX PRI_OTHER_MIN PRI_OTHER_MAX PRI_FG_MIN_NP PRI_FG_MAX_NP PRI_BG_MIN_NP PRI_BG_MAX_NP

Calculate the priority using the appropriate symbols such as PRI_FIFO_MIN or PRI_FIFO_MAX. Avoid using numeric constants as priorities. (Section 2.7 describes how to specify priorities between the minimum and maximum values.)

Description

This routine changes both the current scheduling policy and associated scheduling parameters of the thread specified by thread to the policy and associated parameters provided in policy and param, respectively.

All currently implemented DECthreads scheduling policies have one scheduling parameter called sched_priority. You must specify an appropriate sched_priority parameter for the policy you choose.

Changing the scheduling policy or priority, or both, of a thread can cause it to start executing or to be preempted by another thread. A thread changes its own scheduling policy and priority by using the handle returned by pthread_self.

This routine differs from pthread_attr_setschedpolicy and pthread_attr_setschedparam, in that those routines set the scheduling policy and parameter attributes that are used to establish the priority and scheduling policy of a new thread when it is created. This routine, however, changes the scheduling policy and parameters of an existing thread.

Return Values

If an error condition occurs, no scheduling policy or parameters are changed for the target thread, and this routine returns an integer value indicating the type of error. Possible return values are as follows:

Return Description

0 Successful completion. [EINVAL] The value specified by policy or param is invalid. [ENOTSUP] An attempt is made to set the scheduling policy or a parameter to an unsupported value. [EPERM] The caller does not have the appropriate privileges to set the scheduling policy or parameters of the specified thread. [ESRCH] The value specified by thread does not refer to an existing thread.

Associated Routines

   pthread_attr_getschedparam
   pthread_attr_setschedpolicy
   pthread_create
   pthread_self
   sched_yield