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PTHREAD_GETCONCURRENCY(3) DragonFly Library Functions Manual
pthread_getconcurrency, pthread_setconcurrency - get or set level of
POSIX Threads Library (libpthread, -lpthread)
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.
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.
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.
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
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