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


sched_setparam - set scheduling parameters


#include <sched.h>

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


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

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.


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


The sched_setparam() function will fail if:

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

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().

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


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

|Interface Stability | Committed |
|MT-Level | MT-Safe |
|Standard | See standards(7). |


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

illumos April 1, 2008 SCHED_SETPARAM(3C)