Suspending thread switching while inspecting stacks

  For Modula-3 runtime to work correctly in NPTL threaded environment, I
have to make thread stack image scanning atomic so garbage collector can
scan for traced pointers in local variable storage space for every
thread, while suspending thread switching. For this to work, I have to:

  1. suspend thread switching;
  2. get address of used stack area by pthread_thread_t, for every
stack;
  3. resume thread switching;
  
  Is this doable with nptl?

  Thanks,
  dd