ref: f0ac2d01765f938a4f3656efef440cf2c1bca69d
dir: /sys/src/libc/arm64/lock.c/
#include <u.h> #include <libc.h> extern uintptr _barrier(uintptr); 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); }