mirror of https://github.com/mkerrisk/man-pages
171 lines
6.8 KiB
Plaintext
171 lines
6.8 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "SCHED_SETSCHEDULER" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" sched_setscheduler
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.SH NAME
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sched_setscheduler \- set scheduling policy and parameters (\fBREALTIME\fP)
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.SH SYNOPSIS
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.LP
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\fB#include <sched.h>
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.br
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.sp
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int sched_setscheduler(pid_t\fP \fIpid\fP\fB, int\fP \fIpolicy\fP\fB,
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.br
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\ \ \ \ \ \ const struct sched_param *\fP\fIparam\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fIsched_setscheduler\fP() function shall set the scheduling policy
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and scheduling parameters of the process specified by
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\fIpid\fP to \fIpolicy\fP and the parameters specified in the \fBsched_param\fP
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structure pointed to by \fIparam\fP,
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respectively. The value of the \fIsched_priority\fP member in the
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\fBsched_param\fP structure shall be any integer within the
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inclusive priority range for the scheduling policy specified by \fIpolicy\fP.
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If the value of \fIpid\fP is negative, the behavior
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of the \fIsched_setscheduler\fP() function is unspecified.
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.LP
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The possible values for the \fIpolicy\fP parameter are defined in
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the \fI<sched.h>\fP header.
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.LP
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If a process specified by \fIpid\fP exists, and if the calling process
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has permission, the scheduling policy and scheduling
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parameters shall be set for the process whose process ID is equal
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to \fIpid\fP.
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.LP
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If \fIpid\fP is zero, the scheduling policy and scheduling parameters
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shall be set for the calling process.
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.LP
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The conditions under which one process has the appropriate privilege
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to change the scheduling parameters of another process are
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implementation-defined.
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.LP
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Implementations may require that the requesting process have permission
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to set its own scheduling parameters or those of another
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process. Additionally, implementation-defined restrictions may apply
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as to the appropriate privileges required to set a process'
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own scheduling policy, or another process' scheduling policy, to a
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particular value.
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.LP
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The \fIsched_setscheduler\fP() function shall be considered successful
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if it succeeds in setting the scheduling policy and
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scheduling parameters of the process specified by \fIpid\fP to the
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values specified by \fIpolicy\fP and the structure pointed to
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by \fIparam\fP, respectively.
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.LP
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If
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the scheduling policy specified by \fIpolicy\fP is SCHED_SPORADIC,
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the value specified by the \fIsched_ss_low_priority\fP member
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of the \fIparam\fP argument shall be any integer within the inclusive
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priority range for the sporadic server policy. The
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\fIsched_ss_repl_period\fP and \fIsched_ss_init_budget\fP members
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of the \fIparam\fP argument shall represent the time
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parameters used by the sporadic server scheduling policy for the target
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process. The \fIsched_ss_max_repl\fP member of the
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\fIparam\fP argument shall represent the maximum number of replenishments
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that are allowed to be pending simultaneously for the
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process scheduled under this scheduling policy.
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.LP
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The specified \fIsched_ss_repl_period\fP shall be greater than or
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equal to the specified \fIsched_ss_init_budget\fP for the
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function to succeed; if it is not, then the function shall fail.
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.LP
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The value of \fIsched_ss_max_repl\fP shall be within the inclusive
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range [1, {SS_REPL_MAX}] for the function to succeed; if
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not, the function shall fail.
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.LP
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If the scheduling policy specified by \fIpolicy\fP is either SCHED_FIFO
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or SCHED_RR, the \fIsched_ss_low_priority\fP,
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\fIsched_ss_repl_period\fP, and \fIsched_ss_init_budget\fP members
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of the \fIparam\fP argument shall have no effect on the
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scheduling behavior.
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.LP
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The effect of this function on individual threads is dependent on
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the scheduling contention scope of the threads:
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.IP " *" 3
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For threads with system scheduling contention scope, these functions
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shall have no effect on their scheduling.
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.LP
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.IP " *" 3
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For threads with process scheduling contention scope, the threads'
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scheduling policy and associated parameters shall not be
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affected. However, the scheduling of these threads with respect to
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threads in other processes may be dependent on the scheduling
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parameters of their process, which are governed using these functions.
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.LP
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.LP
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If an implementation supports a two-level scheduling model in which
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library threads are multiplexed on top of several
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kernel-scheduled entities, then the underlying kernel-scheduled entities
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for the system contention scope threads shall not be
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affected by these functions.
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.LP
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The underlying kernel-scheduled entities for the process contention
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scope threads shall have their scheduling policy and
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associated scheduling parameters changed to the values specified in
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\fIpolicy\fP and \fIparam\fP, respectively. Kernel-scheduled
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entities for use by process contention scope threads that are created
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after this call completes shall inherit their scheduling
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policy and associated scheduling parameters from the process.
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.LP
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This function is not atomic with respect to other threads in the process.
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Threads may continue to execute while this function
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call is in the process of changing the scheduling policy and associated
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scheduling parameters for the underlying kernel-scheduled
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entities used by the process contention scope threads.
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.SH RETURN VALUE
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.LP
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Upon successful completion, the function shall return the former scheduling
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policy of the specified process. If the
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\fIsched_setscheduler\fP() function fails to complete successfully,
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the policy and scheduling parameters shall remain unchanged,
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and the function shall return a value of -1 and set \fIerrno\fP to
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indicate the error.
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.SH ERRORS
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.LP
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The \fIsched_setscheduler\fP() function shall fail if:
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.TP 7
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.B EINVAL
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The value of the \fIpolicy\fP parameter is invalid, or one or more
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of the parameters contained in \fIparam\fP is outside the
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valid range for the specified scheduling policy.
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.TP 7
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.B EPERM
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The requesting process does not have permission to set either or both
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of the scheduling parameters or the scheduling policy of
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the specified process.
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.TP 7
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.B ESRCH
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No process can be found corresponding to that specified by \fIpid\fP.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.LP
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None.
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIsched_getparam\fP() , \fIsched_getscheduler\fP() ,
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\fIsched_setparam\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001,
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\fI<sched.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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