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