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- #include <u.h>
- #include <libc.h>
- void
- lock(Lock *lk)
- {
- int i;
- /* once fast */
- if(!_tas(&lk->val))
- return;
- /* a thousand times pretty fast */
- for(i=0; i<1000; i++){
- if(!_tas(&lk->val))
- return;
- sleep(0);
- }
- /* now nice and slow */
- for(i=0; i<1000; i++){
- if(!_tas(&lk->val))
- return;
- sleep(100);
- }
- /* take your time */
- while(_tas(&lk->val))
- sleep(1000);
- }
- int
- canlock(Lock *lk)
- {
- if(_tas(&lk->val))
- return 0;
- return 1;
- }
- void
- unlock(Lock *lk)
- {
- lk->val = 0;
- }
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