ref: 47c188c0c6c2a013aded790bcaa5c9640955e38b
dir: /sys/src/ape/lib/ap/arm64/lock.c/
#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); }