fusl/src/thread/__unmapself.c

#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);
}