NAME
pthread_getconcurrency,
pthread_setconcurrency —
get or set level of
concurrency
LIBRARY
library “libpthread”
SYNOPSIS
#include
<pthread.h>
int
pthread_getconcurrency(void);
int
pthread_setconcurrency(int
new_level);
DESCRIPTION
Thepthread_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”).