src/stdio/__lockfile.c

   1 #include "stdio_impl.h"
   2 #include "pthread_impl.h"
   3
   4 int __lockfile(FILE *f)
   5 {
   6         int owner = f->lock, tid = __pthread_self()->tid;
   7         if ((owner & ~MAYBE_WAITERS) == tid)
   8                 return 0;
   9         owner = a_cas(&f->lock, 0, tid);
  10         if (!owner) return 1;
  11         while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) {
  12                 if ((owner & MAYBE_WAITERS) ||
  13                     a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner)
  14                         __futexwait(&f->lock, owner|MAYBE_WAITERS, 1);
  15         }
  16         return 1;
  17 }
  18
  19 void __unlockfile(FILE *f)
  20 {
  21         if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
  22                 __wake(&f->lock, 1, 1);
  23 }