ref: 5935eeb6de5597072b083fadbcc3f9e94d1e36c1
dir: /sys/src/libthread/xincport.h/
#include <u.h> #include <libc.h> #include <thread.h> static Lock l; void _xinc(long *p) { lock(&l); (*p)++; unlock(&l); } long _xdec(long *p) { long r; lock(&l); r = --(*p); unlock(&l); return r; }