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SCHED_SETPARAM(2) | System Calls Manual | SCHED_SETPARAM(2) |
NAME¶
sched_setparam
,
sched_getparam
—
set/get scheduling parameters
LIBRARY¶
Standard C Library (libc, -lc)SYNOPSIS¶
#include
<sched.h>
int
sched_setparam
(pid_t
pid, const
struct sched_param *param);
int
sched_getparam
(pid_t
pid, struct
sched_param *param);
DESCRIPTION¶
Thesched_setparam
() system call 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
param structure must 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.
In this implementation, if the value of pid is
negative the system call will fail.
If a process specified by pid exists and if the
calling process has permission, the scheduling parameters are set for the
process whose process ID is equal to pid.
If pid is zero, the scheduling parameters are
set for the calling process.
In this implementation, the policy of when a process can affect the scheduling
parameters of another process is specified in IEEE
Std 1003.1b-1993 (“POSIX.1b”) as a write-style operation.
The target process, whether it is running or not running, will resume 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
will 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 nonempty process lists, then the
process that is the head of the highest priority list will 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.
In this implementation, when the current scheduling policy for the process
specified by pid is normal timesharing
(SCHED_OTHER, aka SCHED_NORMAL when not POSIX-source) or the idle policy
(SCHED_IDLE when not POSIX-source) then the behavior is as if the process had
been running under SCHED_RR with a priority lower than any actual realtime
priority.
The sched_getparam
() system call will return
the scheduling parameters of a process specified by
pid in the
sched_param structure pointed to by
param.
If a process specified by pid exists and if the
calling process has permission, the scheduling parameters for the process
whose process ID is equal to pid are
returned.
In this implementation, the policy of when a process can obtain the scheduling
parameters of another process are detailed in IEEE
Std 1003.1b-1993 (“POSIX.1b”) as a read-style operation.
If pid is zero, the scheduling parameters for
the calling process will be returned. In this implementation, the
sched_getparam system call will fail if
pid is negative.
RETURN VALUES¶
Upon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.ERRORS¶
On failure errno will be set to the corresponding value:- [
ENOSYS
] - The system is not configured to support this functionality.
- [
EPERM
] - The requesting process doesn not have permission as detailed in IEEE Std 1003.1b-1993 (“POSIX.1b”).
- [
ESRCH
] - No process can be found corresponding to that specified by pid.
- [
EINVAL
] - For
sched_setparam
(): one or more of the requested scheduling parameters is outside the range defined for the scheduling policy of the specified pid.
SEE ALSO¶
sched_get_priority_max(2), sched_get_priority_min(2), sched_getscheduler(2), sched_rr_get_interval(2), sched_setscheduler(2), sched_yield(2)STANDARDS¶
Thesched_setparam
() and
sched_getparam
() system calls conform to
IEEE Std 1003.1b-1993
(“POSIX.1b”).March 12, 1998 | Debian |