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 int ftrylockfile(FILE *f)
  24 {
  25         pthread_t self = __pthread_self();
  26         int tid = self->tid;
  27         int owner = f->lock;
  28         if ((owner & ~MAYBE_WAITERS) == tid) {
  29                 if (f->lockcount == LONG_MAX)
  30                         return -1;
  31                 f->lockcount++;
  32                 return 0;
  33         }
  34         if (owner < 0) f->lock = owner = 0;
  35         if (owner || a_cas(&f->lock, 0, tid))
  36                 return -1;
  37         f->lockcount = 1;
  38         f->prev_locked = 0;
  39         f->next_locked = self->stdio_locks;
  40         if (f->next_locked) f->next_locked->prev_locked = f;
  41         self->stdio_locks = f;
  42         return 0;
  43 }