Index for Section 3

Alphabetical listing for S

Bottom of page

sched_setparam(3)
NAME
  sched_setparam - Sets the scheduling parameters of the specified process
  (P1003.1b)

SYNOPSIS
  #include <sched.h>

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

LIBRARY
  Realtime Library (librt.so, librt.a)

PARAMETERS
  pid Specifies the ID of the process whose scheduling parameters are set. If
      pid is zero, the scheduling parameters of the calling process are set.

  *param
      Specifies a pointer to a sched_param structure, which contains the
      scheduling parameters of the specified process. Currently, the
      sched_param structure contains only a priority field. The value of the
      priority value is any integer within the priority range for the current
      scheduling policy of the process specified by pid.

DESCRIPTION
  The sched_setparam function changes the scheduling parameters of a process.
  Setting priorities such that the most critical process has the highest
  priority allows applications to determine more effectively when a process
  will run.

  At run time, a process starts out with an initial priority of
  SCHED_PRIO_USER_MAX.	A call to the sched_setparam function that raises the
  priority of a process also raises the maximum priority for the process.
  This higher maximum priority exists for the life of the process or until
  the priority is set to a new, higher priority through another call to the
  sched_setparam function. The maximum priority cannot be adjusted downward,
  but subsequent calls to the sched_setparam or sched_setscheduler functions
  can specify that a process run at a lower priority.

  You must have superuser privileges to set the priority above the user
  maximum, SCHED_PRIO_USER_MAX. A superuser can set the priority outside the
  range of the specified pid's scheduling policy.

  When the function completes, the target process resumes execution after all
  other runnable processes of equal or greater priority are scheduled to run.
  If the priority of the target process is set higher than that of the
  calling process, and if the target process is ready to run, then the target
  process will preempt the calling process. If the calling process set its
  own priority lower than some other process, then the other process will
  preempt the calling process. In either situation, the calling process might
  not receive notification of the completion of the requested priority change
  until the target process has executed.

  The scheduling parameters of the process as indicated by pid are obtained
  with a call to the sched_getparam function.

  The priority of a process is inherited across fork and exec calls.

RETURN VALUES
  On a successful call to the sched_setparam function, the scheduling
  parameters are set and a value of 0 (zero) is returned. On an unsuccessful
  call, a value of -1 is returned and errno is set to indicate that an error
  occurred and the priority is unchanged.

ERRORS
  The sched_setparam function fails under the following conditions:

  [EINVAL]
      One or more of the requested scheduling parameters is outside the range
      defined for the specified pid's scheduling policy.  This error does not
      apply for superusers.

  [EPERM]
      The requesting process does not have permission to set the scheduling
      parameters for the specified process, nor does it have appropriate
      privilege to invoke the sched_setparam function.

  [ESRCH]
      No process can be found corresponding to that specified by pid.

SEE ALSO
  Functions: getpid(2), sched_getparam(3), sched_getscheduler(3),
  sched_setscheduler(3)

  Guide to Realtime Programming

Index for Section 3

Alphabetical listing for S

Top of page