SCHED_SETPARAM(3C) Standard C Library Functions SCHED_SETPARAM(3C)

NAME

sched_setparam - set scheduling parameters

SYNOPSIS

#include <sched.h>

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

DESCRIPTION

The sched_setparam() function 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 sched_param structure is 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. If the value of pid is negative, the behavior of
the sched_setparam() function is unspecified.


If a process specified by pid exists and if the calling process has
permission, the scheduling parameters will be set for the process
whose process ID is equal to pid. The real or effective user ID of
the calling process must match the real or saved (from exec(2)) user
ID of the target process unless the effective user ID of the calling
process is 0. See Intro(2).


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


The target process, whether it is running or not running, resumes
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 preempts a lowest priority running process. Similarly, if
the process calling sched_setparam() sets its own priority lower than
that of one or more other non-empty process lists, then the process
that is the head of the highest priority list also preempts 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.

RETURN VALUES

If successful, the sched_setparam() function returns 0.


If the call to sched_setparam() is unsuccessful, the priority remains
unchanged, and the function returns -1 and sets errno to indicate the
error.

ERRORS

The sched_setparam() function will fail if:

EINVAL
One or more of the requested scheduling parameters is
outside the range defined for the scheduling policy of the
specified pid.


EPERM
The requesting process does not have permission to set the
scheduling parameters for the specified process, or does
not have the appropriate privilege to invoke
sched_setparam().


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

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | MT-Safe |
+--------------------+-------------------+
|Standard | See standards(7). |
+--------------------+-------------------+

SEE ALSO

Intro(2), exec(2), sched_getparam(3C), sched_getscheduler(3C),
sched_setscheduler(3C), sched.h(3HEAD), librt(3LIB), attributes(7),
standards(7)

April 1, 2008 SCHED_SETPARAM(3C)