PTHREAD_ATTR_SETSCOPE(3) Linux Programmer's Manual PTHREAD_ATTR_SETSCOPE(3) NAME pthread_attr_setscope, pthread_attr_getscope - set/get contention scope attribute in thread attributes object SYNOPSIS #include <pthread.h> int pthread_attr_setscope(pthread_attr_t *attr, int scope); int pthread_attr_getscope(const pthread_attr_t *attr, int *scope); Compile and link with -pthread. DESCRIPTION The pthread_attr_setscope() function sets the contention scope attribute of the thread attributes object referred to by attr to the value specified in scope. The contention scope attribute defines the set of threads against which a thread competes for resources such as the CPU. POSIX.1-2001 specifies two possible values for scope: PTHREAD_SCOPE_SYSTEM The thread competes for resources with all other threads in all processes on the system that are in the same scheduling alloca- tion domain (a group of one or more processors). PTHREAD_SCOPE_SYSTEM threads are scheduled relative to one another according to their scheduling policy and priority. PTHREAD_SCOPE_PROCESS The thread competes for resources with all other threads in the same process that were also created with the PTHREAD_SCOPE_PROCESS contention scope. PTHREAD_SCOPE_PROCESS threads are scheduled relative to other threads in the process according to their scheduling policy and priority. POSIX.1-2001 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 PTHREAD_SCOPE_SYSTEM contention scope. POSIX.1-2001 requires that an implementation support at least one of these contention scopes. Linux supports PTHREAD_SCOPE_SYSTEM, but not PTHREAD_SCOPE_PROCESS. On systems that support multiple contention scopes, then, in order for the parameter setting made by pthread_attr_setscope() to have effect when calling pthread_create(3), the caller must use pthread_attr_set- inheritsched(3) to set the inherit-scheduler attribute of the attributes object attr to PTHREAD_EXPLICIT_SCHED. The pthread_attr_getscope() function returns the contention scope attribute of the thread attributes object referred to by attr in the buffer pointed to by scope. RETURN VALUE On success, these functions return 0; on error, they return a nonzero error number. ERRORS pthread_attr_setscope() can fail with the following errors: EINVAL An invalid value was specified in scope. ENOTSUP scope specified the value PTHREAD_SCOPE_PROCESS, which is not supported on Linux. ATTRIBUTES Multithreading (see pthreads(7)) The pthread_attr_setscope() and pthread_attr_getscope() functions are thread-safe. CONFORMING TO POSIX.1-2001. NOTES The 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 imple- mentation and the modern NPTL implementation, which are both 1:1 threading implementations. POSIX.1-2001 specifies that the default contention scope is implementa- tion-defined. SEE ALSO pthread_attr_init(3), pthread_attr_setaffinity_np(3), pthread_attr_setinheritsched(3), pthread_attr_setschedparam(3), pthread_attr_setschedpolicy(3), pthread_create(3), pthreads(7) COLOPHON This page is part of release 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/. Linux 2014-05-28 PTHREAD_ATTR_SETSCOPE(3)
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