ref: b9c1eaa2de919a6c1a323826eba1a9e63e3d149c
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;
}