Originální popis anglicky:
sched_setparam - set scheduling parameters (
REALTIME)
Návod, kniha: POSIX Programmer's Manual
#include <sched.h>
int sched_setparam(pid_t
pid, const struct
sched_param *param);
The
sched_setparam() function shall set 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 shall 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. 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 shall be set for the process whose
process ID is equal to
pid.
If
pid is zero, the scheduling parameters shall be set for the calling
process.
The conditions under which one process has permission to change the scheduling
parameters of another process are implementation-defined.
Implementations may require the requesting process to have the appropriate
privilege to set its own scheduling parameters or those of another process.
The target process, whether it is running or not running, shall be moved to the
tail of the thread list for its priority.
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
shall 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 non-empty process lists, then the process that is the head of
the highest priority list shall 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.
If the scheduling policy of the target process 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 to be 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 of the target process 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. If the scheduling policy of this process is
not SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the effects of these members are
implementation-defined; this case includes the SCHED_OTHER policy.
If the current scheduling policy for the process specified by
pid is not
SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the result is
implementation-defined; this case includes the SCHED_OTHER policy.
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 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 parameters changed to the value specified
in
param. 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 for the underlying kernel-scheduled entities
used by the process contention scope threads.
If successful, the
sched_setparam() function shall return zero.
If the call to
sched_setparam() is unsuccessful, the priority shall
remain unchanged, and the function shall return a value of -1 and set
errno to indicate the error.
The
sched_setparam() function shall 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.
The following sections are informative.
None.
None.
None.
None.
sched_getparam() ,
sched_getscheduler() ,
sched_setscheduler() , 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
.
