_callout_stop_safe
_callout_stop_safe(&hpts->co, 0);
._callout_stop_safe = _callout_stop_safe,
#define _callout_stop_safe pace->funcs->_callout_stop_safe
rv = _callout_stop_safe(&hpts->co, CS_DRAIN);
int (*_callout_stop_safe)(struct callout *c, int flags);
._callout_stop_safe = test_callout_stop_safe,
#define callout_stop(c) _callout_stop_safe(c, 0)
int _callout_stop_safe(struct callout *, int);
#define callout_drain(c) _callout_stop_safe(c, CS_DRAIN)