timerfd_state
state->tfd_next = timerfd_state;
timerfd_state = state;
struct timerfd_state;
typedef struct timerfd_state timerfd_state_t;
for (sp = &timerfd_state; *sp != state; sp = &((*sp)->tfd_next))
static timerfd_state_t *timerfd_state; /* global list of state */