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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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SCHED_SETSCHEDULER(3P) POSIX Programmer's Manual SCHED_SETSCHEDULER(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
sched_setscheduler — set scheduling policy and parameters
(REALTIME)
#include <sched.h>
int sched_setscheduler(pid_t pid, int policy,
const struct sched_param *param);
The sched_setscheduler() function shall set the scheduling policy
and scheduling parameters of the process specified by pid to
policy and the parameters specified in the sched_param structure
pointed to by param, respectively. The value of the sched_priority
member in the sched_param structure shall be any integer within
the inclusive priority range for the scheduling policy specified
by policy. If the value of pid is negative, the behavior of the
sched_setscheduler() function is unspecified.
The possible values for the policy parameter are defined in the
<sched.h> header.
If a process specified by pid exists, and if the calling process
has permission, the scheduling policy and scheduling parameters
shall be set for the process whose process ID is equal to pid.
If pid is zero, the scheduling policy and scheduling parameters
shall be set for the calling process.
The conditions under which one process has appropriate privileges
to change the scheduling parameters of another process are
implementation-defined.
Implementations may require that the requesting process have
permission to set its own scheduling parameters or those of
another process. Additionally, implementation-defined
restrictions may apply as to the appropriate privileges required
to set the scheduling policy of the process, or the scheduling
policy of another process, to a particular value.
The sched_setscheduler() function shall be considered successful
if it succeeds in setting the scheduling policy and scheduling
parameters of the process specified by pid to the values specified
by policy and the structure pointed to by param, respectively.
See Scheduling Policies for a description on how this function
affects the scheduling of the threads within the target process.
If the current scheduling policy for the target process is not
SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the result is
implementation-defined; this case includes the SCHED_OTHER policy.
The specified sched_ss_repl_period shall be greater than or equal
to the specified sched_ss_init_budget for the function to succeed;
if it is not, then the function shall fail.
The value of sched_ss_max_repl shall be within the inclusive range
[1,{SS_REPL_MAX}] for the function to succeed; if not, the
function shall fail. It is unspecified whether the
sched_ss_repl_period and sched_ss_init_budget values are stored as
provided by this function or are rounded to align with the
resolution of the clock being used.
This function is not atomic with respect to other threads in the
process. Threads may continue to execute while this function call
is in the process of changing the scheduling policy and associated
scheduling parameters for the underlying kernel-scheduled entities
used by the process contention scope threads.
Upon successful completion, the function shall return the former
scheduling policy of the specified process. If the
sched_setscheduler() function fails to complete successfully, the
policy and scheduling parameters shall remain unchanged, and the
function shall return a value of -1 and set errno to indicate the
error.
The sched_setscheduler() function shall fail if:
EINVAL The value of the policy parameter is invalid, or one or
more of the parameters contained in param is outside the
valid range for the specified scheduling policy.
EPERM The requesting process does not have permission to set
either or both of the scheduling parameters or the
scheduling policy of the specified process.
ESRCH No process can be found corresponding to that specified by
pid.
The following sections are informative.
None.
None.
None.
None.
Scheduling Policies, sched_getparam(3p), sched_getscheduler(3p),
sched_setparam(3p)
The Base Definitions volume of POSIX.1‐2017, sched.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 SCHED_SETSCHEDULER(3P)
Pages that refer to this page: sched.h(0p), getpriority(3p), posix_spawn(3p), sched_getparam(3p), sched_get_priority_max(3p), sched_getscheduler(3p), sched_rr_get_interval(3p), sched_setparam(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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