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#define _LOCK_EXTENSION
#include "../plan9/sys9.h"
#include <lock.h>
extern int tas(int*);
extern unsigned long long _barrier(unsigned long long);
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)
{
return tas(&lk->val) == 0;
}
void
unlock(Lock *lk)
{
lk->val = _barrier(0);
}
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