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| .TH PTHREAD_ATTR_SETSCOPE 3 2017-09-15 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| pthread_attr_setscope, pthread_attr_getscope \- set/get contention scope |
| attribute in thread attributes object |
| .SH SYNOPSIS |
| .nf |
| .B #include <pthread.h> |
| .PP |
| .BI "int pthread_attr_setscope(pthread_attr_t *" attr \ |
| ", int " scope ); |
| .BI "int pthread_attr_getscope(const pthread_attr_t *" attr \ |
| ", int *" scope ); |
| .PP |
| Compile and link with \fI\-pthread\fP. |
| .fi |
| .SH DESCRIPTION |
| The |
| .BR pthread_attr_setscope () |
| function sets the contention scope attribute of the |
| thread attributes object referred to by |
| .I attr |
| to the value specified in |
| .IR scope . |
| The contention scope attribute defines the set of threads |
| against which a thread competes for resources such as the CPU. |
| POSIX.1 specifies two possible values for |
| .IR scope : |
| .TP |
| .B PTHREAD_SCOPE_SYSTEM |
| The thread competes for resources with all other threads |
| in all processes on the system that are in the same scheduling |
| allocation domain (a group of one or more processors). |
| .B PTHREAD_SCOPE_SYSTEM |
| threads are scheduled relative to one another |
| according to their scheduling policy and priority. |
| .TP |
| .B PTHREAD_SCOPE_PROCESS |
| The thread competes for resources with all other threads |
| in the same process that were also created with the |
| .BR PTHREAD_SCOPE_PROCESS |
| contention scope. |
| .BR PTHREAD_SCOPE_PROCESS |
| threads are scheduled relative to other threads in the process |
| according to their scheduling policy and priority. |
| POSIX.1 leaves it unspecified how these threads contend |
| with other threads in other process on the system or |
| with other threads in the same process that |
| were created with the |
| .B PTHREAD_SCOPE_SYSTEM |
| contention scope. |
| .PP |
| POSIX.1 requires that an implementation support at least one of these |
| contention scopes. |
| Linux supports |
| .BR PTHREAD_SCOPE_SYSTEM , |
| but not |
| .BR PTHREAD_SCOPE_PROCESS . |
| .PP |
| On systems that support multiple contention scopes, then, |
| in order for the parameter setting made by |
| .BR pthread_attr_setscope () |
| to have effect when calling |
| .BR pthread_create (3), |
| the caller must use |
| .BR pthread_attr_setinheritsched (3) |
| to set the inherit-scheduler attribute of the attributes object |
| .I attr |
| to |
| .BR PTHREAD_EXPLICIT_SCHED . |
| .PP |
| The |
| .BR pthread_attr_getscope () |
| function returns the contention scope attribute of the |
| thread attributes object referred to by |
| .I attr |
| in the buffer pointed to by |
| .IR scope . |
| .SH RETURN VALUE |
| On success, these functions return 0; |
| on error, they return a nonzero error number. |
| .SH ERRORS |
| .BR pthread_attr_setscope () |
| can fail with the following errors: |
| .TP |
| .B EINVAL |
| An invalid value was specified in |
| .IR scope . |
| .TP |
| .B ENOTSUP |
| .IR scope |
| specified the value |
| .BR PTHREAD_SCOPE_PROCESS , |
| which is not supported on Linux. |
| .SH ATTRIBUTES |
| For an explanation of the terms used in this section, see |
| .BR attributes (7). |
| .TS |
| allbox; |
| lbw24 lb lb |
| l l l. |
| Interface Attribute Value |
| T{ |
| .BR pthread_attr_setscope (), |
| .BR pthread_attr_getscope () |
| T} Thread safety MT-Safe |
| .TE |
| .SH CONFORMING TO |
| POSIX.1-2001, POSIX.1-2008. |
| .SH NOTES |
| The |
| .B PTHREAD_SCOPE_SYSTEM |
| contention scope typically indicates that a user-space thread is |
| bound directly to a single kernel-scheduling entity. |
| This is the case on Linux for the obsolete LinuxThreads implementation |
| and the modern NPTL implementation, |
| which are both 1:1 threading implementations. |
| .PP |
| POSIX.1 specifies that the default contention scope is |
| implementation-defined. |
| .SH SEE ALSO |
| .ad l |
| .nh |
| .BR pthread_attr_init (3), |
| .BR pthread_attr_setaffinity_np (3), |
| .BR pthread_attr_setinheritsched (3), |
| .BR pthread_attr_setschedparam (3), |
| .BR pthread_attr_setschedpolicy (3), |
| .BR pthread_create (3), |
| .BR pthreads (7) |