In a resource manager, I tried to control the thread number in the thread pool by thread_pool_limits as below,


  /* make resource manager single threaded */
  thread_pool_limits(tpp, 0, 0, 1, 1, 0);

  /* do something */

  /* return the thread pool to its initial state */
  thread_pool_limits(tpp, 3, 4, 5, 1, THREAD_POOL_CONTROL_NONBLOCK);

Normally, it works fine. However, if the system is very busy, the second call to thread_pool_limits was blocked. By 
using pidin, I saw 12 threads in thread pool, even the maximum thread number is set to 5 in thread_pool_limits(). And 
the function thread_pool_limits() will return until all other threads finish execution. Is it normal?

Thanks,
Jianwei