text: #include "pthread_impl.h"
  #include "atomic.h"
  #include "syscall.h"
  /* cheat and reuse CRTJMP macro from dynlink code */
  #include "dynlink.h"
  
  static volatile int lock;
  static void *unmap_base;
  static size_t unmap_size;
  static char shared_stack[256];
  
  static void do_unmap()
  {
  	__syscall(SYS_munmap, unmap_base, unmap_size);
  	__syscall(SYS_exit);
  }
  
  void __unmapself(void *base, size_t size)
  {
  	int tid=__pthread_self()->tid;
  	char *stack = shared_stack + sizeof shared_stack;
  	stack -= (uintptr_t)stack % 16;
  	while (lock || a_cas(&lock, 0, tid))
  		a_spin();
  	__syscall(SYS_set_tid_address, &lock);
  	unmap_base = base;
  	unmap_size = size;
  	CRTJMP(do_unmap, stack);
  }
  