NAME

       sched_setparam, sched_getparam — set/get scheduling parameters

LIBRARY

       Standard C Library (libc, -lc)

SYNOPSIS

       #include <sched.h>

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

       int
       sched_getparam(pid_t pid, struct sched_param *param);

DESCRIPTION

       The  sched_setparam()  system  call sets the scheduling parameters of the process specified by pid to the
       values specified by the sched_param structure pointed to by  param.   The  value  of  the  sched_priority
       member  in  the  param  structure must be any integer within the inclusive priority range for the current
       scheduling policy of the process specified by pid.  Higher numerical values for  the  priority  represent
       higher priorities.

       In this implementation, if the value of pid is negative the system call will fail.

       If a process specified by pid exists and if the calling process has permission, the scheduling parameters
       are set for the process whose process ID is equal to pid.

       If pid is zero, the scheduling parameters are set for the calling process.

       In  this  implementation,  the  policy  of when a process can affect the scheduling parameters of another
       process is specified in IEEE Std 1003.1b-1993 (“POSIX.1”) as a write-style operation.

       The target process, whether it is running or not running, will resume execution after all other  runnable
       processes of equal or greater priority have been scheduled to run.

       If  the  priority  of  the  process  specified  by the pid argument is set higher than that of the lowest
       priority running process and if the specified process is ready to run, the process specified by  the  pid
       argument   will   preempt  a  lowest  priority  running  process.   Similarly,  if  the  process  calling
       sched_setparam() sets its own priority lower than that of one or more other nonempty process lists,  then
       the  process  that is the head of the highest priority list will also preempt the calling process.  Thus,
       in either case, the originating process might not receive notification of the completion of the requested
       priority change until the higher priority process has executed.

       In this implementation, when the current scheduling policy for the process specified  by  pid  is  normal
       timesharing (SCHED_OTHER, aka SCHED_NORMAL when not POSIX-source) or the idle policy (SCHED_IDLE when not
       POSIX-source)  then  the  behavior  is  as if the process had been running under SCHED_RR with a priority
       lower than any actual realtime priority.

       The sched_getparam() system call will return the scheduling parameters of a process specified by  pid  in
       the sched_param structure pointed to by param.

       If a process specified by pid exists and if the calling process has permission, the scheduling parameters
       for the process whose process ID is equal to pid are returned.

       In  this  implementation,  the  policy  of when a process can obtain the scheduling parameters of another
       process are detailed in IEEE Std 1003.1b-1993 (“POSIX.1”) as a read-style operation.

       If pid is  zero,  the  scheduling  parameters  for  the  calling  process  will  be  returned.   In  this
       implementation, the sched_getparam system call will fail if pid is negative.

RETURN VALUES

       Upon  successful  completion,  the value 0 is returned; otherwise the value -1 is returned and the global
       variable errno is set to indicate the error.

ERRORS

       On failure errno will be set to the corresponding value:

       [ENOSYS]           The system is not configured to support this functionality.

       [EPERM]            The requesting process doesn not have permission as detailed in IEEE Std  1003.1b-1993
                          (“POSIX.1”).

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

       [EINVAL]           For  sched_setparam():  one  or more of the requested scheduling parameters is outside
                          the range defined for the scheduling policy of the specified pid.

SEE ALSO

       sched_get_priority_max(2),  sched_get_priority_min(2),  sched_getscheduler(2),  sched_rr_get_interval(2),
       sched_setscheduler(2), sched_yield(2)

STANDARDS

       The sched_setparam() and sched_getparam() system calls conform to IEEE Std 1003.1b-1993 (“POSIX.1”).

Debian                                           March 12, 1998                                SCHED_SETPARAM(2)