nsz Git - musl/blob - src/stdio/ftrylockfile.c

   1 #include "stdio_impl.h"
   2 #include "pthread_impl.h"
   3 #include <limits.h>
   4
   5 #define MAYBE_WAITERS 0x40000000
   6
   7 void __do_orphaned_stdio_locks()
   8 {
   9         FILE *f;
  10         for (f=__pthread_self()->stdio_locks; f; f=f->next_locked)
  11                 a_store(&f->lock, 0x40000000);
  12 }
  13
  14 void __unlist_locked_file(FILE *f)
  15 {
  16         if (f->lockcount) {
  17                 if (f->next_locked) f->next_locked->prev_locked = f->prev_locked;
  18                 if (f->prev_locked) f->prev_locked->next_locked = f->next_locked;
  19                 else __pthread_self()->stdio_locks = f->next_locked;
  20         }
  21 }
  22
  23 void __register_locked_file(FILE *f, pthread_t self)
  24 {
  25         f->lockcount = 1;
  26         f->prev_locked = 0;
  27         f->next_locked = self->stdio_locks;
  28         if (f->next_locked) f->next_locked->prev_locked = f;
  29         self->stdio_locks = f;
  30 }
  31
  32 int ftrylockfile(FILE *f)
  33 {
  34         pthread_t self = __pthread_self();
  35         int tid = self->tid;
  36         int owner = f->lock;
  37         if ((owner & ~MAYBE_WAITERS) == tid) {
  38                 if (f->lockcount == LONG_MAX)
  39                         return -1;
  40                 f->lockcount++;
  41                 return 0;
  42         }
  43         if (owner < 0) f->lock = owner = 0;
  44         if (owner || a_cas(&f->lock, 0, tid))
  45                 return -1;
  46         __register_locked_file(f, self);
  47         return 0;
  48 }