static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
const pid_t pid = CPUCLOCK_PID(which_clock);
int error = -EINVAL;
unsigned long long rtn;
if (pid == 0) {
/*
* Special case constant value for our own clocks.
* We don't have to do any lookup to find ourselves.
*/
if (CPUCLOCK_PERTHREAD(which_clock)) {
/*
* Sampling just ourselves we can do with no locking.
*/
error = cpu_clock_sample(which_clock,
current, &rtn);
} else {
read_lock(&tasklist_lock);
error = cpu_clock_sample_group(which_clock,
current, &rtn);
read_unlock(&tasklist_lock);
}
} else {
/*
* Find the given PID, and validate that the caller
* should be able to see it.
*/
struct task_struct *p;
rcu_read_lock();
p = find_task_by_vpid(pid);
if (p) {
if (CPUCLOCK_PERTHREAD(which_clock)) {
if (same_thread_group(p, current)) {
error = cpu_clock_sample(which_clock,
p, &rtn);
}
} else {
read_lock(&tasklist_lock);
if (thread_group_leader(p) && p->sighand) {
error =
cpu_clock_sample_group(which_clock,
p, &rtn);
}
read_unlock(&tasklist_lock);
}
}
rcu_read_unlock();
}
if (error)
return error;
sample_to_timespec(which_clock, rtn, tp);
return 0;
}
static int posix_cpu_clock_get_task(struct task_struct *tsk,
const clockid_t which_clock,
struct timespec *tp)
{
int err = -EINVAL;
unsigned long long rtn;
if (CPUCLOCK_PERTHREAD(which_clock)) {
if (same_thread_group(tsk, current))
err = cpu_clock_sample(which_clock, tsk, &rtn);
} else {
unsigned long flags;
struct sighand_struct *sighand;
/*
* while_each_thread() is not yet entirely RCU safe,
* keep locking the group while sampling process
* clock for now.
*/
sighand = lock_task_sighand(tsk, &flags);
if (!sighand)
return err;
if (tsk == current || thread_group_leader(tsk))
err = cpu_clock_sample_group(which_clock, tsk, &rtn);
unlock_task_sighand(tsk, &flags);
}
if (!err)
sample_to_timespec(which_clock, rtn, tp);
return err;
}
static int posix_cpu_clock_get_task(struct task_struct *tsk,
const clockid_t which_clock,
struct timespec *tp)
{
int err = -EINVAL;
unsigned long long rtn;
if (CPUCLOCK_PERTHREAD(which_clock)) {
if (same_thread_group(tsk, current))
err = cpu_clock_sample(which_clock, tsk, &rtn);
} else {
if (tsk == current || thread_group_leader(tsk))
err = cpu_clock_sample_group(which_clock, tsk, &rtn);
}
if (!err)
sample_to_timespec(which_clock, rtn, tp);
return err;
}
