.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved .TH "SCHED_SETSCHEDULER" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual" .\" sched_setscheduler .SH NAME sched_setscheduler \- set scheduling policy and parameters (\fBREALTIME\fP) .SH SYNOPSIS .LP \fB#include .br .sp int sched_setscheduler(pid_t\fP \fIpid\fP\fB, int\fP \fIpolicy\fP\fB, .br \ \ \ \ \ \ const struct sched_param *\fP\fIparam\fP\fB); \fP \fB .br \fP .SH DESCRIPTION .LP The \fIsched_setscheduler\fP() function shall set the scheduling policy and scheduling parameters of the process specified by \fIpid\fP to \fIpolicy\fP and the parameters specified in the \fBsched_param\fP structure pointed to by \fIparam\fP, respectively. The value of the \fIsched_priority\fP member in the \fBsched_param\fP structure shall be any integer within the inclusive priority range for the scheduling policy specified by \fIpolicy\fP. If the value of \fIpid\fP is negative, the behavior of the \fIsched_setscheduler\fP() function is unspecified. .LP The possible values for the \fIpolicy\fP parameter are defined in the \fI\fP header. .LP If a process specified by \fIpid\fP 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 \fIpid\fP. .LP If \fIpid\fP is zero, the scheduling policy and scheduling parameters shall be set for the calling process. .LP The conditions under which one process has the appropriate privilege to change the scheduling parameters of another process are implementation-defined. .LP 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. .LP The \fIsched_setscheduler\fP() function shall be considered successful if it succeeds in setting the scheduling policy and scheduling parameters of the process specified by \fIpid\fP to the values specified by \fIpolicy\fP and the structure pointed to by \fIparam\fP, respectively. .LP If the scheduling policy specified by \fIpolicy\fP is SCHED_SPORADIC, the value specified by the \fIsched_ss_low_priority\fP member of the \fIparam\fP argument shall be any integer within the inclusive priority range for the sporadic server policy. The \fIsched_ss_repl_period\fP and \fIsched_ss_init_budget\fP members of the \fIparam\fP argument shall represent the time parameters used by the sporadic server scheduling policy for the target process. The \fIsched_ss_max_repl\fP member of the \fIparam\fP argument shall represent the maximum number of replenishments that are allowed to be pending simultaneously for the process scheduled under this scheduling policy. .LP The specified \fIsched_ss_repl_period\fP shall be greater than or equal to the specified \fIsched_ss_init_budget\fP for the function to succeed; if it is not, then the function shall fail. .LP The value of \fIsched_ss_max_repl\fP shall be within the inclusive range [1, {SS_REPL_MAX}] for the function to succeed; if not, the function shall fail. .LP If the scheduling policy specified by \fIpolicy\fP is either SCHED_FIFO or SCHED_RR, the \fIsched_ss_low_priority\fP, \fIsched_ss_repl_period\fP, and \fIsched_ss_init_budget\fP members of the \fIparam\fP argument shall have no effect on the scheduling behavior. .LP The effect of this function on individual threads is dependent on the scheduling contention scope of the threads: .IP " *" 3 For threads with system scheduling contention scope, these functions shall have no effect on their scheduling. .LP .IP " *" 3 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. .LP .LP 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. .LP 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 \fIpolicy\fP and \fIparam\fP, 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. .LP 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. .SH RETURN VALUE .LP Upon successful completion, the function shall return the former scheduling policy of the specified process. If the \fIsched_setscheduler\fP() function fails to complete successfully, the policy and scheduling parameters shall remain unchanged, and the function shall return a value of -1 and set \fIerrno\fP to indicate the error. .SH ERRORS .LP The \fIsched_setscheduler\fP() function shall fail if: .TP 7 .B EINVAL The value of the \fIpolicy\fP parameter is invalid, or one or more of the parameters contained in \fIparam\fP is outside the valid range for the specified scheduling policy. .TP 7 .B 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. .TP 7 .B ESRCH No process can be found corresponding to that specified by \fIpid\fP. .sp .LP \fIThe following sections are informative.\fP .SH EXAMPLES .LP None. .SH APPLICATION USAGE .LP None. .SH RATIONALE .LP None. .SH FUTURE DIRECTIONS .LP None. .SH SEE ALSO .LP \fIsched_getparam\fP() , \fIsched_getscheduler\fP() , \fIsched_setparam\fP() , the Base Definitions volume of IEEE\ Std\ 1003.1-2001, \fI\fP .SH COPYRIGHT 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 .