/*
* Calculate the absolute or boot-relative time from the
* machine-specific fast timecounter and the published timehands
* structure read from the shared page.
*
* The lockless reading scheme is similar to the one used to read the
* in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
* is based on the kernel implementation.
*/
static int
binuptime(struct bintime *bt, struct vdso_timekeep *tk, int abs)
{
struct vdso_timehands *th;
uint32_t curr, gen;
u_int delta;
int error;
do {
if (!tk->tk_enabled)
return (ENOSYS);
curr = atomic_load_acq_32(&tk->tk_current);
th = &tk->tk_th[curr];
gen = atomic_load_acq_32(&th->th_gen);
*bt = th->th_offset;
error = tc_delta(th, &delta);
if (error == EAGAIN)
continue;
if (error != 0)
return (error);
bintime_addx(bt, th->th_scale * delta);
if (abs)
bintime_add(bt, &th->th_boottime);
/*
* Ensure that the load of th_offset is completed
* before the load of th_gen.
*/
atomic_thread_fence_acq();
} while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
return (0);
}
/*
* Calculate the absolute or boot-relative time from the
* machine-specific fast timecounter and the published timehands
* structure read from the shared page.
*
* The lockless reading scheme is similar to the one used to read the
* in-kernel timehands, see sys/kern/kern_tc.c:binuptime(). This code
* is based on the kernel implementation.
*/
static int
binuptime(struct bintime *bt, struct vdso_timekeep *tk, int abs)
{
struct vdso_timehands *th;
uint32_t curr, gen;
do {
if (!tk->tk_enabled)
return (ENOSYS);
curr = atomic_load_acq_32(&tk->tk_current);
th = &tk->tk_th[curr];
if (th->th_algo != VDSO_TH_ALGO_1)
return (ENOSYS);
gen = atomic_load_acq_32(&th->th_gen);
*bt = th->th_offset;
bintime_addx(bt, th->th_scale * tc_delta(th));
if (abs)
bintime_add(bt, &th->th_boottime);
/*
* Ensure that the load of th_offset is completed
* before the load of th_gen.
*/
atomic_thread_fence_acq();
} while (curr != tk->tk_current || gen == 0 || gen != th->th_gen);
return (0);
}
