sched_setparam()

Updated: May 06, 2022

Change the priority of a process

Synopsis:

#include <sched.h>

int sched_setparam( 
          pid_t pid,
          const struct sched_param *param );

Arguments:

pid
The ID of the process whose priority you want to set, or 0 to set it for the current process.
param
A pointer to a sched_param structure whose sched_priority member holds the priority that you want to assign to the process.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The sched_setparam() function changes the priority of process pid to that of the sched_priority member in the sched_param structure pointed to by param. If pid is zero, the priority of the calling process is changed.

Note:
  • In QNX Neutrino, scheduling is associated with threads, not processes, so sched_setparam() sets the scheduling parameters for thread 1 in the process pid, or for the calling thread if pid is 0.
  • In order to set the priority for a process whose user ID is different from the calling process's real or effective user ID, your process must have the PROCMGR_AID_SCHEDULE ability enabled. In order to change its priority to a value above the maximum permitted for unprivileged processes, your process must have the PROCMGR_AID_PRIORITY ability enabled. For more information, see procmgr_ability().

The sched_priority member in param must lie between the minimum and maximum values returned by sched_get_priority_max() and sched_get_priority_min().

By default, the process priority and scheduling policy are inherited from or explicitly set by the parent process. Once running, the child process may change its priority by using this function.

Returns:

0
Success.
-1
An error occurred (errno is set).

Errors:

EFAULT
A fault occurred while trying to access the buffers provided.
EINVAL
The priority isn't a valid priority.
EPERM
The calling process doesn't have the required permission; see procmgr_ability().
ESRCH
The process pid doesn't exist.

Classification:

POSIX 1003.1 PS

Safety:  
Cancellation point No
Interrupt handler No
Signal handler Yes
Thread Yes