ref: b2f53f0261b11c2ed6655f4087f3bf9aa0eb1c36
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;
}