get or set level of
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
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.
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
pthread_getconcurrency() returns zero.
pthread_setconcurrency() will fail if:
- The value specified by new_level is negative.
- The value specified by new_level would cause a system resource to be exceeded.
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_setconcurrency() functions since their use
may conflict with an application's use of these functions.
pthread_setconcurrency() functions conform to
Version 2 of the Single UNIX Specification