1SCHED_SETPARAM(3P) POSIX Programmer's Manual SCHED_SETPARAM(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_setparam - set scheduling parameters (REALTIME)
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15 #include <sched.h>
16 int sched_setparam(pid_t pid, const struct sched_param *param);
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21 The sched_setparam() function shall set the scheduling parameters of
22 the process specified by pid to the values specified by the sched_param
23 structure pointed to by param. The value of the sched_priority member
24 in the sched_param structure shall be any integer within the inclusive
25 priority range for the current scheduling policy of the process speci‐
26 fied by pid. Higher numerical values for the priority represent higher
27 priorities. If the value of pid is negative, the behavior of the
28 sched_setparam() function is unspecified.
29 If a process specified by pid exists, and if the calling process has
31 permission, the scheduling parameters shall be set for the process
32 whose process ID is equal to pid.
33 If pid is zero, the scheduling parameters shall be set for the calling
35 process.
36 The conditions under which one process has permission to change the
38 scheduling parameters of another process are implementation-defined.
39 Implementations may require the requesting process to have the appro‐
41 priate privilege to set its own scheduling parameters or those of
42 another process.
43 The target process, whether it is running or not running, shall be
45 moved to the tail of the thread list for its priority.
46 If the priority of the process specified by the pid argument is set
48 higher than that of the lowest priority running process and if the
49 specified process is ready to run, the process specified by the pid
50 argument shall preempt a lowest priority running process. Similarly, if
51 the process calling sched_setparam() sets its own priority lower than
52 that of one or more other non-empty process lists, then the process
53 that is the head of the highest priority list shall also preempt the
54 calling process. Thus, in either case, the originating process might
55 not receive notification of the completion of the requested priority
56 change until the higher priority process has executed.
57 If the scheduling policy of the target process is SCHED_SPORADIC, the
59 value specified by the sched_ss_low_priority member of the param argu‐
60 ment shall be any integer within the inclusive priority range for the
61 sporadic server policy. The sched_ss_repl_period and sched_ss_init_bud‐
62 get members of the param argument shall represent the time parameters
63 to be used by the sporadic server scheduling policy for the target
64 process. The sched_ss_max_repl member of the param argument shall rep‐
65 resent the maximum number of replenishments that are allowed to be
66 pending simultaneously for the process scheduled under this scheduling
67 policy.
68 The specified sched_ss_repl_period shall be greater than or equal to
70 the specified sched_ss_init_budget for the function to succeed; if it
71 is not, then the function shall fail.
72 The value of sched_ss_max_repl shall be within the inclusive range [1,
74 {SS_REPL_MAX}] for the function to succeed; if not, the function shall
75 fail.
76 If the scheduling policy of the target process is either SCHED_FIFO or
78 SCHED_RR, the sched_ss_low_priority, sched_ss_repl_period, and
79 sched_ss_init_budget members of the param argument shall have no effect
80 on the scheduling behavior. If the scheduling policy of this process is
81 not SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the effects of these mem‐
82 bers are implementation-defined; this case includes the SCHED_OTHER
83 policy.
84 If the current scheduling policy for the process specified by pid is
86 not SCHED_FIFO, SCHED_RR, or SCHED_SPORADIC, the result is implementa‐
87 tion-defined; this case includes the SCHED_OTHER policy.
88 The effect of this function on individual threads is dependent on the
90 scheduling contention scope of the threads:
91 * For threads with system scheduling contention scope, these functions
93 shall have no effect on their scheduling.
94 * For threads with process scheduling contention scope, the threads'
96 scheduling parameters shall not be affected. However, the scheduling
97 of these threads with respect to threads in other processes may be
98 dependent on the scheduling parameters of their process, which are
99 governed using these functions.
100 If an implementation supports a two-level scheduling model in which
102 library threads are multiplexed on top of several kernel-scheduled
103 entities, then the underlying kernel-scheduled entities for the system
104 contention scope threads shall not be affected by these functions.
105 The underlying kernel-scheduled entities for the process contention
107 scope threads shall have their scheduling parameters changed to the
108 value specified in param. Kernel-scheduled entities for use by process
109 contention scope threads that are created after this call completes
110 shall inherit their scheduling policy and associated scheduling parame‐
111 ters from the process.
112 This function is not atomic with respect to other threads in the
114 process. Threads may continue to execute while this function call is
115 in the process of changing the scheduling policy for the underlying
116 kernel-scheduled entities used by the process contention scope threads.
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119 If successful, the sched_setparam() function shall return zero.
120 If the call to sched_setparam() is unsuccessful, the priority shall
122 remain unchanged, and the function shall return a value of -1 and set
123 errno to indicate the error.
124
126 The sched_setparam() function shall fail if:
127 EINVAL One or more of the requested scheduling parameters is outside
129 the range defined for the scheduling policy of the specified
130 pid.
131 EPERM The requesting process does not have permission to set the
133 scheduling parameters for the specified process, or does not
134 have the appropriate privilege to invoke sched_setparam().
135 ESRCH No process can be found corresponding to that specified by pid.
137 The following sections are informative.
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142 None.
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145 None.
146
148 None.
149
151 None.
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154 sched_getparam(), sched_getscheduler(), sched_setscheduler(), the Base
155 Definitions volume of IEEE Std 1003.1-2001, <sched.h>
156
158 Portions of this text are reprinted and reproduced in electronic form
159 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
160 -- Portable Operating System Interface (POSIX), The Open Group Base
161 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
162 Electrical and Electronics Engineers, Inc and The Open Group. In the
163 event of any discrepancy between this version and the original IEEE and
164 The Open Group Standard, the original IEEE and The Open Group Standard
165 is the referee document. The original Standard can be obtained online
166 at http://www.opengroup.org/unix/online.html .
167IEEE/The Open Group 2003 SCHED_SETPARAM(3P)