PTHREAD_GETCONCURRENCY(3) OpenBSD Programmer's Manual
PTHREAD_GETCONCURRENCY(3)NAME
pthread_getconcurrency, pthread_setconcurrency - get or set level of
concurrency
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.
ERRORSpthread_setconcurrency() 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.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9
