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PTHREAD_GETCONCURRENCY(3)                   DragonFly Library Functions Manual


NAME

     pthread_getconcurrency, pthread_setconcurrency - get or set level of
     concurrency


LIBRARY

     POSIX Threads Library (libpthread, -lpthread)


SYNOPSIS

     #include <pthread.h>

     int
     pthread_getconcurrency(void);

     int
     pthread_setconcurrency(int new_level);


DESCRIPTION

     The pthread_getconcurrency() function allows an application to inform the
     threads implementation of its desired concurrency level, new_level.  The
     actual level of concurrency provided by the implementation as a result of
     this function call is unspecified.  If new_level is zero, it causes the
     implementation to maintain the concurrency level at its discretion as if
     pthread_setconcurrency() was never called.  The pthread_getconcurrency()
     function returns the value set by a previous call to the
     pthread_setconcurrency() function.  If the pthread_setconcurrency()
     function was not previously called, this function returns zero to
     indicate that the implementation is maintaining the concurrency level.
     When an application calls pthread_setconcurrency(), it is informing the
     implementation of its desired concurrency level.  The implementation uses
     this as a hint, not a requirement.


RETURN VALUES

     If successful, the pthread_setconcurrency() function returns zero.
     Otherwise, an error number is returned to indicate the error.  The
     pthread_getconcurrency() function always returns the concurrency level
     set by a previous call to pthread_setconcurrency().  If the
     pthread_setconcurrency() function has never been called,
     pthread_getconcurrency() returns zero.


ERRORS

     The pthread_setconcurrency() function will fail if:

     [EINVAL]           The value specified by new_level is negative.

     [EAGAIN]           The value specified by new_level would cause a system
                        resource to be exceeded.


APPLICATION USAGE

     Use of these functions changes the state of the underlying concurrency
     upon which the application depends.  Library developers are advised to
     not use the pthread_getconcurrency() and pthread_setconcurrency()
     functions since their use may conflict with an application's use of these
     functions.


STANDARDS

     The pthread_getconcurrency() and pthread_setconcurrency() functions
     conform to Version 2 of the Single UNIX Specification ("SUSv2").

DragonFly 5.9-DEVELOPMENT        July 10, 2009       DragonFly 5.9-DEVELOPMENT

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