Originální popis anglicky:
sched_setscheduler - set scheduling policy and parameters (
REALTIME)
Návod, kniha: POSIX Programmer's Manual
#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 the appropriate privilege 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 a process' own scheduling policy, or another process'
scheduling policy, 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.
If the scheduling policy specified by
policy is SCHED_SPORADIC, the value
specified by the
sched_ss_low_priority member of the
param
argument shall be any integer within the inclusive priority range for the
sporadic server policy. The
sched_ss_repl_period and
sched_ss_init_budget members of the
param argument shall
represent the time parameters used by the sporadic server scheduling policy
for the target process. The
sched_ss_max_repl member of the
param argument shall represent the maximum number of replenishments
that are allowed to be pending simultaneously for the process scheduled under
this scheduling 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.
If the scheduling policy specified by
policy is either SCHED_FIFO or
SCHED_RR, the
sched_ss_low_priority,
sched_ss_repl_period, and
sched_ss_init_budget members of the
param argument shall have no
effect on the scheduling behavior.
The effect of this function on individual threads is dependent on the scheduling
contention scope of the threads:
- *
- For threads with system scheduling contention scope, these
functions shall have no effect on their scheduling.
- *
- For threads with process scheduling contention scope, the
threads' scheduling policy and associated parameters shall not be
affected. However, the scheduling of these threads with respect to threads
in other processes may be dependent on the scheduling parameters of their
process, which are governed using these functions.
If an implementation supports a two-level scheduling model in which library
threads are multiplexed on top of several kernel-scheduled entities, then the
underlying kernel-scheduled entities for the system contention scope threads
shall not be affected by these functions.
The underlying kernel-scheduled entities for the process contention scope
threads shall have their scheduling policy and associated scheduling
parameters changed to the values specified in
policy and
param,
respectively. Kernel-scheduled entities for use by process contention scope
threads that are created after this call completes shall inherit their
scheduling policy and associated scheduling parameters from the process.
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.
sched_getparam() ,
sched_getscheduler() ,
sched_setparam()
, the Base Definitions volume of IEEE Std 1003.1-2001,
<sched.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 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
.
