1SCHED_SETSCHEDULER(3P) POSIX Programmer's Manual SCHED_SETSCHEDULER(3P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
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12 sched_setscheduler - set scheduling policy and parameters (REALTIME)
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15 #include <sched.h>
16 int sched_setscheduler(pid_t pid, int policy,
18 const struct sched_param *param);
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22 The sched_setscheduler() function shall set the scheduling policy and
23 scheduling parameters of the process specified by pid to policy and the
24 parameters specified in the sched_param structure pointed to by param,
25 respectively. The value of the sched_priority member in the sched_param
26 structure shall be any integer within the inclusive priority range for
27 the scheduling policy specified by policy. If the value of pid is neg‐
28 ative, the behavior of the sched_setscheduler() function is unspeci‐
29 fied.
30 The possible values for the policy parameter are defined in the
32 <sched.h> header.
33 If a process specified by pid exists, and if the calling process has
35 permission, the scheduling policy and scheduling parameters shall be
36 set for the process whose process ID is equal to pid.
37 If pid is zero, the scheduling policy and scheduling parameters shall
39 be set for the calling process.
40 The conditions under which one process has the appropriate privilege to
42 change the scheduling parameters of another process are implementation-
43 defined.
44 Implementations may require that the requesting process have permission
46 to set its own scheduling parameters or those of another process. Addi‐
47 tionally, implementation-defined restrictions may apply as to the
48 appropriate privileges required to set a process' own scheduling pol‐
49 icy, or another process' scheduling policy, to a particular value.
50 The sched_setscheduler() function shall be considered successful if it
52 succeeds in setting the scheduling policy and scheduling parameters of
53 the process specified by pid to the values specified by policy and the
54 structure pointed to by param, respectively.
55 If the scheduling policy specified by policy is SCHED_SPORADIC, the
57 value specified by the sched_ss_low_priority member of the param argu‐
58 ment shall be any integer within the inclusive priority range for the
59 sporadic server policy. The sched_ss_repl_period and sched_ss_init_bud‐
60 get members of the param argument shall represent the time parameters
61 used by the sporadic server scheduling policy for the target process.
62 The sched_ss_max_repl member of the param argument shall represent the
63 maximum number of replenishments that are allowed to be pending simul‐
64 taneously for the process scheduled under this scheduling policy.
65 The specified sched_ss_repl_period shall be greater than or equal to
67 the specified sched_ss_init_budget for the function to succeed; if it
68 is not, then the function shall fail.
69 The value of sched_ss_max_repl shall be within the inclusive range [1,
71 {SS_REPL_MAX}] for the function to succeed; if not, the function shall
72 fail.
73 If the scheduling policy specified by policy is either SCHED_FIFO or
75 SCHED_RR, the sched_ss_low_priority, sched_ss_repl_period, and
76 sched_ss_init_budget members of the param argument shall have no effect
77 on the scheduling behavior.
78 The effect of this function on individual threads is dependent on the
80 scheduling contention scope of the threads:
81 * For threads with system scheduling contention scope, these functions
83 shall have no effect on their scheduling.
84 * For threads with process scheduling contention scope, the threads'
86 scheduling policy and associated parameters shall not be affected.
87 However, the scheduling of these threads with respect to threads in
88 other processes may be dependent on the scheduling parameters of
89 their process, which are governed using these functions.
90 If an implementation supports a two-level scheduling model in which
92 library threads are multiplexed on top of several kernel-scheduled
93 entities, then the underlying kernel-scheduled entities for the system
94 contention scope threads shall not be affected by these functions.
95 The underlying kernel-scheduled entities for the process contention
97 scope threads shall have their scheduling policy and associated sched‐
98 uling parameters changed to the values specified in policy and param,
99 respectively. Kernel-scheduled entities for use by process contention
100 scope threads that are created after this call completes shall inherit
101 their scheduling policy and associated scheduling parameters from the
102 process.
103 This function is not atomic with respect to other threads in the
105 process. Threads may continue to execute while this function call is
106 in the process of changing the scheduling policy and associated sched‐
107 uling parameters for the underlying kernel-scheduled entities used by
108 the process contention scope threads.
109
111 Upon successful completion, the function shall return the former sched‐
112 uling policy of the specified process. If the sched_setscheduler()
113 function fails to complete successfully, the policy and scheduling
114 parameters shall remain unchanged, and the function shall return a
115 value of -1 and set errno to indicate the error.
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118 The sched_setscheduler() function shall fail if:
119 EINVAL The value of the policy parameter is invalid, or one or more of
121 the parameters contained in param is outside the valid range for
122 the specified scheduling policy.
123 EPERM The requesting process does not have permission to set either or
125 both of the scheduling parameters or the scheduling policy of
126 the specified process.
127 ESRCH No process can be found corresponding to that specified by pid.
129 The following sections are informative.
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134 None.
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137 None.
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140 None.
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143 None.
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146 sched_getparam(), sched_getscheduler(), sched_setparam(), the Base Def‐
147 initions volume of IEEE Std 1003.1-2001, <sched.h>
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150 Portions of this text are reprinted and reproduced in electronic form
151 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
152 -- Portable Operating System Interface (POSIX), The Open Group Base
153 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
154 Electrical and Electronics Engineers, Inc and The Open Group. In the
155 event of any discrepancy between this version and the original IEEE and
156 The Open Group Standard, the original IEEE and The Open Group Standard
157 is the referee document. The original Standard can be obtained online
158 at http://www.opengroup.org/unix/online.html .
159IEEE/The Open Group 2003 SCHED_SETSCHEDULER(3P)