sys/src/libc/port/lock.c

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