sys/src/libc/arm64/lock.c

   1 #include <u.h>
   2 #include <libc.h>
   3
   4 extern uintptr _barrier(uintptr);
   5
   6 void
   7 lock(Lock *lk)
   8 {
   9         int i;
  10
  11         /* once fast */
  12         if(!_tas(&lk->val))
  13                 return;
  14         /* a thousand times pretty fast */
  15         for(i=0; i<1000; i++){
  16                 if(!_tas(&lk->val))
  17                         return;
  18                 sleep(0);
  19         }
  20         /* now nice and slow */
  21         for(i=0; i<1000; i++){
  22                 if(!_tas(&lk->val))
  23                         return;
  24                 sleep(100);
  25         }
  26         /* take your time */
  27         while(_tas(&lk->val))
  28                 sleep(1000);
  29 }
  30
  31 int
  32 canlock(Lock *lk)
  33 {
  34         return _tas(&lk->val) == 0;
  35 }
  36
  37 void
  38 unlock(Lock *lk)
  39 {
  40         lk->val = _barrier(0);
  41 }