libc-top-half/musl/src/stdio/ftrylockfile.c

   1 #include "stdio_impl.h"
   2 #include "pthread_impl.h"
   3 #include <limits.h>
   4
   5 void __do_orphaned_stdio_locks()
   6 {
   7         FILE *f;
   8         for (f=__pthread_self()->stdio_locks; f; f=f->next_locked)
   9                 a_store(&f->lock, 0x40000000);
  10 }
  11
  12 void __unlist_locked_file(FILE *f)
  13 {
  14         if (f->lockcount) {
  15                 if (f->next_locked) f->next_locked->prev_locked = f->prev_locked;
  16                 if (f->prev_locked) f->prev_locked->next_locked = f->next_locked;
  17                 else __pthread_self()->stdio_locks = f->next_locked;
  18         }
  19 }
  20
  21 void __register_locked_file(FILE *f, pthread_t self)
  22 {
  23         f->lockcount = 1;
  24         f->prev_locked = 0;
  25         f->next_locked = self->stdio_locks;
  26         if (f->next_locked) f->next_locked->prev_locked = f;
  27         self->stdio_locks = f;
  28 }
  29
  30 int ftrylockfile(FILE *f)
  31 {
  32         pthread_t self = __pthread_self();
  33         int tid = self->tid;
  34         int owner = f->lock;
  35         if ((owner & ~MAYBE_WAITERS) == tid) {
  36                 if (f->lockcount == LONG_MAX)
  37                         return -1;
  38                 f->lockcount++;
  39                 return 0;
  40         }
  41         if (owner < 0) f->lock = owner = 0;
  42         if (owner || a_cas(&f->lock, 0, tid))
  43                 return -1;
  44         __register_locked_file(f, self);
  45         return 0;
  46 }