1pthread_attr_setscope(3) Library Functions Manual pthread_attr_setscope(3)
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6 pthread_attr_setscope, pthread_attr_getscope - set/get contention scope
7 attribute in thread attributes object
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10 POSIX threads library (libpthread, -lpthread)
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13 #include <pthread.h>
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15 int pthread_attr_setscope(pthread_attr_t *attr, int scope);
16 int pthread_attr_getscope(const pthread_attr_t *restrict attr,
17 int *restrict scope);
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20 The pthread_attr_setscope() function sets the contention scope attri‐
21 bute of the thread attributes object referred to by attr to the value
22 specified in scope. The contention scope attribute defines the set of
23 threads against which a thread competes for resources such as the CPU.
24 POSIX.1 specifies two possible values for scope:
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26 PTHREAD_SCOPE_SYSTEM
27 The thread competes for resources with all other threads in all
28 processes on the system that are in the same scheduling alloca‐
29 tion domain (a group of one or more processors).
30 PTHREAD_SCOPE_SYSTEM threads are scheduled relative to one an‐
31 other according to their scheduling policy and priority.
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33 PTHREAD_SCOPE_PROCESS
34 The thread competes for resources with all other threads in the
35 same process that were also created with the
36 PTHREAD_SCOPE_PROCESS contention scope. PTHREAD_SCOPE_PROCESS
37 threads are scheduled relative to other threads in the process
38 according to their scheduling policy and priority. POSIX.1
39 leaves it unspecified how these threads contend with other
40 threads in other process on the system or with other threads in
41 the same process that were created with the PTHREAD_SCOPE_SYSTEM
42 contention scope.
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44 POSIX.1 requires that an implementation support at least one of these
45 contention scopes. Linux supports PTHREAD_SCOPE_SYSTEM, but not
46 PTHREAD_SCOPE_PROCESS.
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48 On systems that support multiple contention scopes, then, in order for
49 the parameter setting made by pthread_attr_setscope() to have effect
50 when calling pthread_create(3), the caller must use pthread_attr_set‐
51 inheritsched(3) to set the inherit-scheduler attribute of the at‐
52 tributes object attr to PTHREAD_EXPLICIT_SCHED.
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54 The pthread_attr_getscope() function returns the contention scope at‐
55 tribute of the thread attributes object referred to by attr in the buf‐
56 fer pointed to by scope.
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59 On success, these functions return 0; on error, they return a nonzero
60 error number.
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63 pthread_attr_setscope() can fail with the following errors:
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65 EINVAL An invalid value was specified in scope.
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67 ENOTSUP
68 scope specified the value PTHREAD_SCOPE_PROCESS, which is not
69 supported on Linux.
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72 For an explanation of the terms used in this section, see at‐
73 tributes(7).
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75 ┌────────────────────────────────────────────┬───────────────┬─────────┐
76 │Interface │ Attribute │ Value │
77 ├────────────────────────────────────────────┼───────────────┼─────────┤
78 │pthread_attr_setscope(), │ Thread safety │ MT-Safe │
79 │pthread_attr_getscope() │ │ │
80 └────────────────────────────────────────────┴───────────────┴─────────┘
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83 POSIX.1-2008.
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86 POSIX.1-2001.
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89 The PTHREAD_SCOPE_SYSTEM contention scope typically indicates that a
90 user-space thread is bound directly to a single kernel-scheduling enti‐
91 ty. This is the case on Linux for the obsolete LinuxThreads implemen‐
92 tation and the modern NPTL implementation, which are both 1:1 threading
93 implementations.
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95 POSIX.1 specifies that the default contention scope is implementation-
96 defined.
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99 pthread_attr_init(3), pthread_attr_setaffinity_np(3),
100 pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3),
101 pthread_attr_setschedpolicy(3), pthread_create(3), pthreads(7)
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105Linux man-pages 6.04 2023-03-30 pthread_attr_setscope(3)