<commit_before>/*
 * Implement CPU time clocks for the POSIX clock interface.
 */

#include <linux/sched.h>
#include <linux/posix-timers.h>
#include <linux/errno.h>
#include <linux/math64.h>
#include <asm/uaccess.h>
#include <linux/kernel_stat.h>
#include <trace/events/timer.h>
#include <linux/random.h>
#include <linux/tick.h>
#include <linux/workqueue.h>

/*
 * Called after updating RLIMIT_CPU to run cpu timer and update
 * tsk->signal->cputime_expires expiration cache if necessary. Needs
 * siglock protection since other code may update expiration cache as
 * well.
 */
void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
{
	cputime_t cputime = secs_to_cputime(rlim_new);

	spin_lock_irq(&task->sighand->siglock);
	set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
	spin_unlock_irq(&task->sighand->siglock);
}

static int check_clock(const clockid_t which_clock)
{
	int error = 0;
	struct task_struct *p;
	const pid_t pid = CPUCLOCK_PID(which_clock);

	if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	if (pid == 0)
		return 0;

	rcu_read_lock();
	p = find_task_by_vpid(pid);
	if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
		   same_thread_group(p, current) : has_group_leader_pid(p))) {
		error = -EINVAL;
	}
	rcu_read_unlock();

	return error;
}

static inline unsigned long long
timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
{
	unsigned long long ret;

	ret = 0;		/* high half always zero when .cpu used */
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		ret = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
	} else {
		ret = cputime_to_expires(timespec_to_cputime(tp));
	}
	return ret;
}

static void sample_to_timespec(const clockid_t which_clock,
			       unsigned long long expires,
			       struct timespec *tp)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
		*tp = ns_to_timespec(expires);
	else
		cputime_to_timespec((__force cputime_t)expires, tp);
}

/*
 * Update expiry time from increment, and increase overrun count,
 * given the current clock sample.
 */
static void bump_cpu_timer(struct k_itimer *timer,
			   unsigned long long now)
{
	int i;
	unsigned long long delta, incr;

	if (timer->it.cpu.incr == 0)
		return;

	if (now < timer->it.cpu.expires)
		return;

	incr = timer->it.cpu.incr;
	delta = now + incr - timer->it.cpu.expires;

	/* Don't use (incr*2 < delta), incr*2 might overflow. */
	for (i = 0; incr < delta - incr; i++)
		incr = incr << 1;

	for (; i >= 0; incr >>= 1, i--) {
		if (delta < incr)
			continue;

		timer->it.cpu.expires += incr;
		timer->it_overrun += 1 << i;
		delta -= incr;
	}
}

/**
 * task_cputime_zero - Check a task_cputime struct for all zero fields.
 *
 * @cputime:	The struct to compare.
 *
 * Checks @cputime to see if all fields are zero.  Returns true if all fields
 * are zero, false if any field is nonzero.
 */
static inline int task_cputime_zero(const struct task_cputime *cputime)
{
	if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
		return 1;
	return 0;
}

static inline unsigned long long prof_ticks(struct task_struct *p)
{
	cputime_t utime, stime;

	task_cputime(p, &utime, &stime);

	return cputime_to_expires(utime + stime);
}
static inline unsigned long long virt_ticks(struct task_struct *p)
{
	cputime_t utime;

	task_cputime(p, &utime, NULL);

	return cputime_to_expires(utime);
}

static int
posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
	int error = check_clock(which_clock);
	if (!error) {
		tp->tv_sec = 0;
		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
		if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
			/*
			 * If sched_clock is using a cycle counter, we
			 * don't have any idea of its true resolution
			 * exported, but it is much more than 1s/HZ.
			 */
			tp->tv_nsec = 1;
		}
	}
	return error;
}

static int
posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
{
	/*
	 * You can never reset a CPU clock, but we check for other errors
	 * in the call before failing with EPERM.
	 */
	int error = check_clock(which_clock);
	if (error == 0) {
		error = -EPERM;
	}
	return error;
}


/*
 * Sample a per-thread clock for the given task.
 */
static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
			    unsigned long long *sample)
{
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		*sample = prof_ticks(p);
		break;
	case CPUCLOCK_VIRT:
		*sample = virt_ticks(p);
		break;
	case CPUCLOCK_SCHED:
		*sample = task_sched_runtime(p);
		break;
	}
	return 0;
}

/*
 * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
 * to avoid race conditions with concurrent updates to cputime.
 */
static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
{
	u64 curr_cputime;
retry:
	curr_cputime = atomic64_read(cputime);
	if (sum_cputime > curr_cputime) {
		if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
			goto retry;
	}
}

static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)
{
	__update_gt_cputime(&cputime_atomic->utime, sum->utime);
	__update_gt_cputime(&cputime_atomic->stime, sum->stime);
	__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
}

/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */
static inline void sample_cputime_atomic(struct task_cputime *times,
					 struct task_cputime_atomic *atomic_times)
{
	times->utime = atomic64_read(&atomic_times->utime);
	times->stime = atomic64_read(&atomic_times->stime);
	times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
}

void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
	struct task_cputime sum;

	/* Check if cputimer isn't running. This is accessed without locking. */
	if (!READ_ONCE(cputimer->running)) {
		/*
		 * The POSIX timer interface allows for absolute time expiry
		 * values through the TIMER_ABSTIME flag, therefore we have
		 * to synchronize the timer to the clock every time we start it.
		 */
		thread_group_cputime(tsk, &sum);
		update_gt_cputime(&cputimer->cputime_atomic, &sum);

		/*
		 * We're setting cputimer->running without a lock. Ensure
		 * this only gets written to in one operation. We set
		 * running after update_gt_cputime() as a small optimization,
		 * but barriers are not required because update_gt_cputime()
		 * can handle concurrent updates.
		 */
		WRITE_ONCE(cputimer->running, 1);
	}
	sample_cputime_atomic(times, &cputimer->cputime_atomic);
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with task sighand lock held for safe while_each_thread()
 * traversal.
 */
static int cpu_clock_sample_group(const clockid_t which_clock,
				  struct task_struct *p,
				  unsigned long long *sample)
{
	struct task_cputime cputime;

	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		thread_group_cputime(p, &cputime);
		*sample = cputime_to_expires(cputime.utime + cputime.stime);
		break;
	case CPUCLOCK_VIRT:
		thread_group_cputime(p, &cputime);
		*sample = cputime_to_expires(cputime.utime);
		break;
	case CPUCLOCK_SCHED:
		thread_group_cputime(p, &cputime);
		*sample = cputime.sum_exec_runtime;
		break;
	}
	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 {
		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;
}


static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
	const pid_t pid = CPUCLOCK_PID(which_clock);
	int err = -EINVAL;

	if (pid == 0) {
		/*
		 * Special case constant value for our own clocks.
		 * We don't have to do any lookup to find ourselves.
		 */
		err = posix_cpu_clock_get_task(current, which_clock, tp);
	} 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)
			err = posix_cpu_clock_get_task(p, which_clock, tp);
		rcu_read_unlock();
	}

	return err;
}


/*
 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 * new timer already all-zeros initialized.
 */
static int posix_cpu_timer_create(struct k_itimer *new_timer)
{
	int ret = 0;
	const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
	struct task_struct *p;

	if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	INIT_LIST_HEAD(&new_timer->it.cpu.entry);

	rcu_read_lock();
	if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
		if (pid == 0) {
			p = current;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !same_thread_group(p, current))
				p = NULL;
		}
	} else {
		if (pid == 0) {
			p = current->group_leader;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !has_group_leader_pid(p))
				p = NULL;
		}
	}
	new_timer->it.cpu.task = p;
	if (p) {
		get_task_struct(p);
	} else {
		ret = -EINVAL;
	}
	rcu_read_unlock();

	return ret;
}

/*
 * Clean up a CPU-clock timer that is about to be destroyed.
 * This is called from timer deletion with the timer already locked.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
static int posix_cpu_timer_del(struct k_itimer *timer)
{
	int ret = 0;
	unsigned long flags;
	struct sighand_struct *sighand;
	struct task_struct *p = timer->it.cpu.task;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Protect against sighand release/switch in exit/exec and process/
	 * thread timer list entry concurrent read/writes.
	 */
	sighand = lock_task_sighand(p, &flags);
	if (unlikely(sighand == NULL)) {
		/*
		 * We raced with the reaping of the task.
		 * The deletion should have cleared us off the list.
		 */
		WARN_ON_ONCE(!list_empty(&timer->it.cpu.entry));
	} else {
		if (timer->it.cpu.firing)
			ret = TIMER_RETRY;
		else
			list_del(&timer->it.cpu.entry);

		unlock_task_sighand(p, &flags);
	}

	if (!ret)
		put_task_struct(p);

	return ret;
}

static void cleanup_timers_list(struct list_head *head)
{
	struct cpu_timer_list *timer, *next;

	list_for_each_entry_safe(timer, next, head, entry)
		list_del_init(&timer->entry);
}

/*
 * Clean out CPU timers still ticking when a thread exited.  The task
 * pointer is cleared, and the expiry time is replaced with the residual
 * time for later timer_gettime calls to return.
 * This must be called with the siglock held.
 */
static void cleanup_timers(struct list_head *head)
{
	cleanup_timers_list(head);
	cleanup_timers_list(++head);
	cleanup_timers_list(++head);
}

/*
 * These are both called with the siglock held, when the current thread
 * is being reaped.  When the final (leader) thread in the group is reaped,
 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 */
void posix_cpu_timers_exit(struct task_struct *tsk)
{
	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
						sizeof(unsigned long long));
	cleanup_timers(tsk->cpu_timers);

}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
	cleanup_timers(tsk->signal->cpu_timers);
}

static inline int expires_gt(cputime_t expires, cputime_t new_exp)
{
	return expires == 0 || expires > new_exp;
}

/*
 * Insert the timer on the appropriate list before any timers that
 * expire later.  This must be called with the sighand lock held.
 */
static void arm_timer(struct k_itimer *timer)
{
	struct task_struct *p = timer->it.cpu.task;
	struct list_head *head, *listpos;
	struct task_cputime *cputime_expires;
	struct cpu_timer_list *const nt = &timer->it.cpu;
	struct cpu_timer_list *next;

	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		head = p->cpu_timers;
		cputime_expires = &p->cputime_expires;
	} else {
		head = p->signal->cpu_timers;
		cputime_expires = &p->signal->cputime_expires;
	}
	head += CPUCLOCK_WHICH(timer->it_clock);

	listpos = head;
	list_for_each_entry(next, head, entry) {
		if (nt->expires < next->expires)
			break;
		listpos = &next->entry;
	}
	list_add(&nt->entry, listpos);

	if (listpos == head) {
		unsigned long long exp = nt->expires;

		/*
		 * We are the new earliest-expiring POSIX 1.b timer, hence
		 * need to update expiration cache. Take into account that
		 * for process timers we share expiration cache with itimers
		 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
		 */

		switch (CPUCLOCK_WHICH(timer->it_clock)) {
		case CPUCLOCK_PROF:
			if (expires_gt(cputime_expires->prof_exp, expires_to_cputime(exp)))
				cputime_expires->prof_exp = expires_to_cputime(exp);
			break;
		case CPUCLOCK_VIRT:
			if (expires_gt(cputime_expires->virt_exp, expires_to_cputime(exp)))
				cputime_expires->virt_exp = expires_to_cputime(exp);
			break;
		case CPUCLOCK_SCHED:
			if (cputime_expires->sched_exp == 0 ||
			    cputime_expires->sched_exp > exp)
				cputime_expires->sched_exp = exp;
			break;
		}
	}
}

/*
 * The timer is locked, fire it and arrange for its reload.
 */
static void cpu_timer_fire(struct k_itimer *timer)
{
	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
		/*
		 * User don't want any signal.
		 */
		timer->it.cpu.expires = 0;
	} else if (unlikely(timer->sigq == NULL)) {
		/*
		 * This a special case for clock_nanosleep,
		 * not a normal timer from sys_timer_create.
		 */
		wake_up_process(timer->it_process);
		timer->it.cpu.expires = 0;
	} else if (timer->it.cpu.incr == 0) {
		/*
		 * One-shot timer.  Clear it as soon as it's fired.
		 */
		posix_timer_event(timer, 0);
		timer->it.cpu.expires = 0;
	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
		/*
		 * The signal did not get queued because the signal
		 * was ignored, so we won't get any callback to
		 * reload the timer.  But we need to keep it
		 * ticking in case the signal is deliverable next time.
		 */
		posix_cpu_timer_schedule(timer);
	}
}

/*
 * Sample a process (thread group) timer for the given group_leader task.
 * Must be called with task sighand lock held for safe while_each_thread()
 * traversal.
 */
static int cpu_timer_sample_group(const clockid_t which_clock,
				  struct task_struct *p,
				  unsigned long long *sample)
{
	struct task_cputime cputime;

	thread_group_cputimer(p, &cputime);
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		*sample = cputime_to_expires(cputime.utime + cputime.stime);
		break;
	case CPUCLOCK_VIRT:
		*sample = cputime_to_expires(cputime.utime);
		break;
	case CPUCLOCK_SCHED:
		*sample = cputime.sum_exec_runtime;
		break;
	}
	return 0;
}

#ifdef CONFIG_NO_HZ_FULL
static void nohz_kick_work_fn(struct work_struct *work)
{
	tick_nohz_full_kick_all();
}

static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);

/*
 * We need the IPIs to be sent from sane process context.
 * The posix cpu timers are always set with irqs disabled.
 */
static void posix_cpu_timer_kick_nohz(void)
{
	if (context_tracking_is_enabled())
		schedule_work(&nohz_kick_work);
}

bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
{
	if (!task_cputime_zero(&tsk->cputime_expires))
		return false;

	/* Check if cputimer is running. This is accessed without locking. */
	if (READ_ONCE(tsk->signal->cputimer.running))
		return false;

	return true;
}
#else
static inline void posix_cpu_timer_kick_nohz(void) { }
#endif

/*
 * Guts of sys_timer_settime for CPU timers.
 * This is called with the timer locked and interrupts disabled.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
			       struct itimerspec *new, struct itimerspec *old)
{
	unsigned long flags;
	struct sighand_struct *sighand;
	struct task_struct *p = timer->it.cpu.task;
	unsigned long long old_expires, new_expires, old_incr, val;
	int ret;

	WARN_ON_ONCE(p == NULL);

	new_expires = timespec_to_sample(timer->it_clock, &new->it_value);

	/*
	 * Protect against sighand release/switch in exit/exec and p->cpu_timers
	 * and p->signal->cpu_timers read/write in arm_timer()
	 */
	sighand = lock_task_sighand(p, &flags);
	/*
	 * If p has just been reaped, we can no
	 * longer get any information about it at all.
	 */
	if (unlikely(sighand == NULL)) {
		return -ESRCH;
	}

	/*
	 * Disarm any old timer after extracting its expiry time.
	 */
	WARN_ON_ONCE(!irqs_disabled());

	ret = 0;
	old_incr = timer->it.cpu.incr;
	old_expires = timer->it.cpu.expires;
	if (unlikely(timer->it.cpu.firing)) {
		timer->it.cpu.firing = -1;
		ret = TIMER_RETRY;
	} else
		list_del_init(&timer->it.cpu.entry);

	/*
	 * We need to sample the current value to convert the new
	 * value from to relative and absolute, and to convert the
	 * old value from absolute to relative.  To set a process
	 * timer, we need a sample to balance the thread expiry
	 * times (in arm_timer).  With an absolute time, we must
	 * check if it's already passed.  In short, we need a sample.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &val);
	} else {
		cpu_timer_sample_group(timer->it_clock, p, &val);
	}

	if (old) {
		if (old_expires == 0) {
			old->it_value.tv_sec = 0;
			old->it_value.tv_nsec = 0;
		} else {
			/*
			 * Update the timer in case it has
			 * overrun already.  If it has,
			 * we'll report it as having overrun
			 * and with the next reloaded timer
			 * already ticking, though we are
			 * swallowing that pending
			 * notification here to install the
			 * new setting.
			 */
			bump_cpu_timer(timer, val);
			if (val < timer->it.cpu.expires) {
				old_expires = timer->it.cpu.expires - val;
				sample_to_timespec(timer->it_clock,
						   old_expires,
						   &old->it_value);
			} else {
				old->it_value.tv_nsec = 1;
				old->it_value.tv_sec = 0;
			}
		}
	}

	if (unlikely(ret)) {
		/*
		 * We are colliding with the timer actually firing.
		 * Punt after filling in the timer's old value, and
		 * disable this firing since we are already reporting
		 * it as an overrun (thanks to bump_cpu_timer above).
		 */
		unlock_task_sighand(p, &flags);
		goto out;
	}

	if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
		new_expires += val;
	}

	/*
	 * Install the new expiry time (or zero).
	 * For a timer with no notification action, we don't actually
	 * arm the timer (we'll just fake it for timer_gettime).
	 */
	timer->it.cpu.expires = new_expires;
	if (new_expires != 0 && val < new_expires) {
		arm_timer(timer);
	}

	unlock_task_sighand(p, &flags);
	/*
	 * Install the new reload setting, and
	 * set up the signal and overrun bookkeeping.
	 */
	timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
						&new->it_interval);

	/*
	 * This acts as a modification timestamp for the timer,
	 * so any automatic reload attempt will punt on seeing
	 * that we have reset the timer manually.
	 */
	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
		~REQUEUE_PENDING;
	timer->it_overrun_last = 0;
	timer->it_overrun = -1;

	if (new_expires != 0 && !(val < new_expires)) {
		/*
		 * The designated time already passed, so we notify
		 * immediately, even if the thread never runs to
		 * accumulate more time on this clock.
		 */
		cpu_timer_fire(timer);
	}

	ret = 0;
 out:
	if (old) {
		sample_to_timespec(timer->it_clock,
				   old_incr, &old->it_interval);
	}
	if (!ret)
		posix_cpu_timer_kick_nohz();
	return ret;
}

static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
{
	unsigned long long now;
	struct task_struct *p = timer->it.cpu.task;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Easy part: convert the reload time.
	 */
	sample_to_timespec(timer->it_clock,
			   timer->it.cpu.incr, &itp->it_interval);

	if (timer->it.cpu.expires == 0) {	/* Timer not armed at all.  */
		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
		return;
	}

	/*
	 * Sample the clock to take the difference with the expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
	} else {
		struct sighand_struct *sighand;
		unsigned long flags;

		/*
		 * Protect against sighand release/switch in exit/exec and
		 * also make timer sampling safe if it ends up calling
		 * thread_group_cputime().
		 */
		sighand = lock_task_sighand(p, &flags);
		if (unlikely(sighand == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 * Call the timer disarmed, nothing else to do.
			 */
			timer->it.cpu.expires = 0;
			sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
					   &itp->it_value);
		} else {
			cpu_timer_sample_group(timer->it_clock, p, &now);
			unlock_task_sighand(p, &flags);
		}
	}

	if (now < timer->it.cpu.expires) {
		sample_to_timespec(timer->it_clock,
				   timer->it.cpu.expires - now,
				   &itp->it_value);
	} else {
		/*
		 * The timer should have expired already, but the firing
		 * hasn't taken place yet.  Say it's just about to expire.
		 */
		itp->it_value.tv_nsec = 1;
		itp->it_value.tv_sec = 0;
	}
}

static unsigned long long
check_timers_list(struct list_head *timers,
		  struct list_head *firing,
		  unsigned long long curr)
{
	int maxfire = 20;

	while (!list_empty(timers)) {
		struct cpu_timer_list *t;

		t = list_first_entry(timers, struct cpu_timer_list, entry);

		if (!--maxfire || curr < t->expires)
			return t->expires;

		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	return 0;
}

/*
 * Check for any per-thread CPU timers that have fired and move them off
 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 */
static void check_thread_timers(struct task_struct *tsk,
				struct list_head *firing)
{
	struct list_head *timers = tsk->cpu_timers;
	struct signal_struct *const sig = tsk->signal;
	struct task_cputime *tsk_expires = &tsk->cputime_expires;
	unsigned long long expires;
	unsigned long soft;

	expires = check_timers_list(timers, firing, prof_ticks(tsk));
	tsk_expires->prof_exp = expires_to_cputime(expires);

	expires = check_timers_list(++timers, firing, virt_ticks(tsk));
	tsk_expires->virt_exp = expires_to_cputime(expires);

	tsk_expires->sched_exp = check_timers_list(++timers, firing,
						   tsk->se.sum_exec_runtime);

	/*
	 * Check for the special case thread timers.
	 */
	soft = READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
	if (soft != RLIM_INFINITY) {
		unsigned long hard =
			READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);

		if (hard != RLIM_INFINITY &&
		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			if (soft < hard) {
				soft += USEC_PER_SEC;
				sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
			}
			printk(KERN_INFO
				"RT Watchdog Timeout: %s[%d]\n",
				tsk->comm, task_pid_nr(tsk));
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
		}
	}
}

static inline void stop_process_timers(struct signal_struct *sig)
{
	struct thread_group_cputimer *cputimer = &sig->cputimer;

	/* Turn off cputimer->running. This is done without locking. */
	WRITE_ONCE(cputimer->running, 0);
}

static u32 onecputick;

static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
			     unsigned long long *expires,
			     unsigned long long cur_time, int signo)
{
	if (!it->expires)
		return;

	if (cur_time >= it->expires) {
		if (it->incr) {
			it->expires += it->incr;
			it->error += it->incr_error;
			if (it->error >= onecputick) {
				it->expires -= cputime_one_jiffy;
				it->error -= onecputick;
			}
		} else {
			it->expires = 0;
		}

		trace_itimer_expire(signo == SIGPROF ?
				    ITIMER_PROF : ITIMER_VIRTUAL,
				    tsk->signal->leader_pid, cur_time);
		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
	}

	if (it->expires && (!*expires || it->expires < *expires)) {
		*expires = it->expires;
	}
}

/*
 * Check for any per-thread CPU timers that have fired and move them
 * off the tsk->*_timers list onto the firing list.  Per-thread timers
 * have already been taken off.
 */
static void check_process_timers(struct task_struct *tsk,
				 struct list_head *firing)
{
	struct signal_struct *const sig = tsk->signal;
	unsigned long long utime, ptime, virt_expires, prof_expires;
	unsigned long long sum_sched_runtime, sched_expires;
	struct list_head *timers = sig->cpu_timers;
	struct task_cputime cputime;
	unsigned long soft;

	/*
	 * Collect the current process totals.
	 */
	thread_group_cputimer(tsk, &cputime);
	utime = cputime_to_expires(cputime.utime);
	ptime = utime + cputime_to_expires(cputime.stime);
	sum_sched_runtime = cputime.sum_exec_runtime;

	prof_expires = check_timers_list(timers, firing, ptime);
	virt_expires = check_timers_list(++timers, firing, utime);
	sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);

	/*
	 * Check for the special case process timers.
	 */
	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
			 SIGPROF);
	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
			 SIGVTALRM);
	soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
	if (soft != RLIM_INFINITY) {
		unsigned long psecs = cputime_to_secs(ptime);
		unsigned long hard =
			READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
		cputime_t x;
		if (psecs >= hard) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (psecs >= soft) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
			if (soft < hard) {
				soft++;
				sig->rlim[RLIMIT_CPU].rlim_cur = soft;
			}
		}
		x = secs_to_cputime(soft);
		if (!prof_expires || x < prof_expires) {
			prof_expires = x;
		}
	}

	sig->cputime_expires.prof_exp = expires_to_cputime(prof_expires);
	sig->cputime_expires.virt_exp = expires_to_cputime(virt_expires);
	sig->cputime_expires.sched_exp = sched_expires;
	if (task_cputime_zero(&sig->cputime_expires))
		stop_process_timers(sig);
}

/*
 * This is called from the signal code (via do_schedule_next_timer)
 * when the last timer signal was delivered and we have to reload the timer.
 */
void posix_cpu_timer_schedule(struct k_itimer *timer)
{
	struct sighand_struct *sighand;
	unsigned long flags;
	struct task_struct *p = timer->it.cpu.task;
	unsigned long long now;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Fetch the current sample and update the timer's expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		if (unlikely(p->exit_state))
			goto out;

		/* Protect timer list r/w in arm_timer() */
		sighand = lock_task_sighand(p, &flags);
		if (!sighand)
			goto out;
	} else {
		/*
		 * Protect arm_timer() and timer sampling in case of call to
		 * thread_group_cputime().
		 */
		sighand = lock_task_sighand(p, &flags);
		if (unlikely(sighand == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 */
			timer->it.cpu.expires = 0;
			goto out;
		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
			unlock_task_sighand(p, &flags);
			/* Optimizations: if the process is dying, no need to rearm */
			goto out;
		}
		cpu_timer_sample_group(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		/* Leave the sighand locked for the call below.  */
	}

	/*
	 * Now re-arm for the new expiry time.
	 */
	WARN_ON_ONCE(!irqs_disabled());
	arm_timer(timer);
	unlock_task_sighand(p, &flags);

	/* Kick full dynticks CPUs in case they need to tick on the new timer */
	posix_cpu_timer_kick_nohz();
out:
	timer->it_overrun_last = timer->it_overrun;
	timer->it_overrun = -1;
	++timer->it_requeue_pending;
}

/**
 * task_cputime_expired - Compare two task_cputime entities.
 *
 * @sample:	The task_cputime structure to be checked for expiration.
 * @expires:	Expiration times, against which @sample will be checked.
 *
 * Checks @sample against @expires to see if any field of @sample has expired.
 * Returns true if any field of the former is greater than the corresponding
 * field of the latter if the latter field is set.  Otherwise returns false.
 */
static inline int task_cputime_expired(const struct task_cputime *sample,
					const struct task_cputime *expires)
{
	if (expires->utime && sample->utime >= expires->utime)
		return 1;
	if (expires->stime && sample->utime + sample->stime >= expires->stime)
		return 1;
	if (expires->sum_exec_runtime != 0 &&
	    sample->sum_exec_runtime >= expires->sum_exec_runtime)
		return 1;
	return 0;
}

/**
 * fastpath_timer_check - POSIX CPU timers fast path.
 *
 * @tsk:	The task (thread) being checked.
 *
 * Check the task and thread group timers.  If both are zero (there are no
 * timers set) return false.  Otherwise snapshot the task and thread group
 * timers and compare them with the corresponding expiration times.  Return
 * true if a timer has expired, else return false.
 */
static inline int fastpath_timer_check(struct task_struct *tsk)
{
	struct signal_struct *sig;
	cputime_t utime, stime;

	task_cputime(tsk, &utime, &stime);

	if (!task_cputime_zero(&tsk->cputime_expires)) {
		struct task_cputime task_sample = {
			.utime = utime,
			.stime = stime,
			.sum_exec_runtime = tsk->se.sum_exec_runtime
		};

		if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
			return 1;
	}

	sig = tsk->signal;
	/* Check if cputimer is running. This is accessed without locking. */
	if (READ_ONCE(sig->cputimer.running)) {
		struct task_cputime group_sample;

		sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);

		if (task_cputime_expired(&group_sample, &sig->cputime_expires))<commit_msg>posix_cpu_timer: Optimize fastpath_timer_check()<commit_after>/*
 * Implement CPU time clocks for the POSIX clock interface.
 */

#include <linux/sched.h>
#include <linux/posix-timers.h>
#include <linux/errno.h>
#include <linux/math64.h>
#include <asm/uaccess.h>
#include <linux/kernel_stat.h>
#include <trace/events/timer.h>
#include <linux/random.h>
#include <linux/tick.h>
#include <linux/workqueue.h>

/*
 * Called after updating RLIMIT_CPU to run cpu timer and update
 * tsk->signal->cputime_expires expiration cache if necessary. Needs
 * siglock protection since other code may update expiration cache as
 * well.
 */
void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
{
	cputime_t cputime = secs_to_cputime(rlim_new);

	spin_lock_irq(&task->sighand->siglock);
	set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
	spin_unlock_irq(&task->sighand->siglock);
}

static int check_clock(const clockid_t which_clock)
{
	int error = 0;
	struct task_struct *p;
	const pid_t pid = CPUCLOCK_PID(which_clock);

	if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	if (pid == 0)
		return 0;

	rcu_read_lock();
	p = find_task_by_vpid(pid);
	if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
		   same_thread_group(p, current) : has_group_leader_pid(p))) {
		error = -EINVAL;
	}
	rcu_read_unlock();

	return error;
}

static inline unsigned long long
timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
{
	unsigned long long ret;

	ret = 0;		/* high half always zero when .cpu used */
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		ret = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
	} else {
		ret = cputime_to_expires(timespec_to_cputime(tp));
	}
	return ret;
}

static void sample_to_timespec(const clockid_t which_clock,
			       unsigned long long expires,
			       struct timespec *tp)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
		*tp = ns_to_timespec(expires);
	else
		cputime_to_timespec((__force cputime_t)expires, tp);
}

/*
 * Update expiry time from increment, and increase overrun count,
 * given the current clock sample.
 */
static void bump_cpu_timer(struct k_itimer *timer,
			   unsigned long long now)
{
	int i;
	unsigned long long delta, incr;

	if (timer->it.cpu.incr == 0)
		return;

	if (now < timer->it.cpu.expires)
		return;

	incr = timer->it.cpu.incr;
	delta = now + incr - timer->it.cpu.expires;

	/* Don't use (incr*2 < delta), incr*2 might overflow. */
	for (i = 0; incr < delta - incr; i++)
		incr = incr << 1;

	for (; i >= 0; incr >>= 1, i--) {
		if (delta < incr)
			continue;

		timer->it.cpu.expires += incr;
		timer->it_overrun += 1 << i;
		delta -= incr;
	}
}

/**
 * task_cputime_zero - Check a task_cputime struct for all zero fields.
 *
 * @cputime:	The struct to compare.
 *
 * Checks @cputime to see if all fields are zero.  Returns true if all fields
 * are zero, false if any field is nonzero.
 */
static inline int task_cputime_zero(const struct task_cputime *cputime)
{
	if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
		return 1;
	return 0;
}

static inline unsigned long long prof_ticks(struct task_struct *p)
{
	cputime_t utime, stime;

	task_cputime(p, &utime, &stime);

	return cputime_to_expires(utime + stime);
}
static inline unsigned long long virt_ticks(struct task_struct *p)
{
	cputime_t utime;

	task_cputime(p, &utime, NULL);

	return cputime_to_expires(utime);
}

static int
posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
	int error = check_clock(which_clock);
	if (!error) {
		tp->tv_sec = 0;
		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
		if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
			/*
			 * If sched_clock is using a cycle counter, we
			 * don't have any idea of its true resolution
			 * exported, but it is much more than 1s/HZ.
			 */
			tp->tv_nsec = 1;
		}
	}
	return error;
}

static int
posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
{
	/*
	 * You can never reset a CPU clock, but we check for other errors
	 * in the call before failing with EPERM.
	 */
	int error = check_clock(which_clock);
	if (error == 0) {
		error = -EPERM;
	}
	return error;
}


/*
 * Sample a per-thread clock for the given task.
 */
static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
			    unsigned long long *sample)
{
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		*sample = prof_ticks(p);
		break;
	case CPUCLOCK_VIRT:
		*sample = virt_ticks(p);
		break;
	case CPUCLOCK_SCHED:
		*sample = task_sched_runtime(p);
		break;
	}
	return 0;
}

/*
 * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
 * to avoid race conditions with concurrent updates to cputime.
 */
static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
{
	u64 curr_cputime;
retry:
	curr_cputime = atomic64_read(cputime);
	if (sum_cputime > curr_cputime) {
		if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
			goto retry;
	}
}

static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)
{
	__update_gt_cputime(&cputime_atomic->utime, sum->utime);
	__update_gt_cputime(&cputime_atomic->stime, sum->stime);
	__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
}

/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */
static inline void sample_cputime_atomic(struct task_cputime *times,
					 struct task_cputime_atomic *atomic_times)
{
	times->utime = atomic64_read(&atomic_times->utime);
	times->stime = atomic64_read(&atomic_times->stime);
	times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
}

void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
	struct task_cputime sum;

	/* Check if cputimer isn't running. This is accessed without locking. */
	if (!READ_ONCE(cputimer->running)) {
		/*
		 * The POSIX timer interface allows for absolute time expiry
		 * values through the TIMER_ABSTIME flag, therefore we have
		 * to synchronize the timer to the clock every time we start it.
		 */
		thread_group_cputime(tsk, &sum);
		update_gt_cputime(&cputimer->cputime_atomic, &sum);

		/*
		 * We're setting cputimer->running without a lock. Ensure
		 * this only gets written to in one operation. We set
		 * running after update_gt_cputime() as a small optimization,
		 * but barriers are not required because update_gt_cputime()
		 * can handle concurrent updates.
		 */
		WRITE_ONCE(cputimer->running, 1);
	}
	sample_cputime_atomic(times, &cputimer->cputime_atomic);
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with task sighand lock held for safe while_each_thread()
 * traversal.
 */
static int cpu_clock_sample_group(const clockid_t which_clock,
				  struct task_struct *p,
				  unsigned long long *sample)
{
	struct task_cputime cputime;

	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		thread_group_cputime(p, &cputime);
		*sample = cputime_to_expires(cputime.utime + cputime.stime);
		break;
	case CPUCLOCK_VIRT:
		thread_group_cputime(p, &cputime);
		*sample = cputime_to_expires(cputime.utime);
		break;
	case CPUCLOCK_SCHED:
		thread_group_cputime(p, &cputime);
		*sample = cputime.sum_exec_runtime;
		break;
	}
	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 {
		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;
}


static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
	const pid_t pid = CPUCLOCK_PID(which_clock);
	int err = -EINVAL;

	if (pid == 0) {
		/*
		 * Special case constant value for our own clocks.
		 * We don't have to do any lookup to find ourselves.
		 */
		err = posix_cpu_clock_get_task(current, which_clock, tp);
	} 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)
			err = posix_cpu_clock_get_task(p, which_clock, tp);
		rcu_read_unlock();
	}

	return err;
}


/*
 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 * new timer already all-zeros initialized.
 */
static int posix_cpu_timer_create(struct k_itimer *new_timer)
{
	int ret = 0;
	const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
	struct task_struct *p;

	if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	INIT_LIST_HEAD(&new_timer->it.cpu.entry);

	rcu_read_lock();
	if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
		if (pid == 0) {
			p = current;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !same_thread_group(p, current))
				p = NULL;
		}
	} else {
		if (pid == 0) {
			p = current->group_leader;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !has_group_leader_pid(p))
				p = NULL;
		}
	}
	new_timer->it.cpu.task = p;
	if (p) {
		get_task_struct(p);
	} else {
		ret = -EINVAL;
	}
	rcu_read_unlock();

	return ret;
}

/*
 * Clean up a CPU-clock timer that is about to be destroyed.
 * This is called from timer deletion with the timer already locked.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
static int posix_cpu_timer_del(struct k_itimer *timer)
{
	int ret = 0;
	unsigned long flags;
	struct sighand_struct *sighand;
	struct task_struct *p = timer->it.cpu.task;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Protect against sighand release/switch in exit/exec and process/
	 * thread timer list entry concurrent read/writes.
	 */
	sighand = lock_task_sighand(p, &flags);
	if (unlikely(sighand == NULL)) {
		/*
		 * We raced with the reaping of the task.
		 * The deletion should have cleared us off the list.
		 */
		WARN_ON_ONCE(!list_empty(&timer->it.cpu.entry));
	} else {
		if (timer->it.cpu.firing)
			ret = TIMER_RETRY;
		else
			list_del(&timer->it.cpu.entry);

		unlock_task_sighand(p, &flags);
	}

	if (!ret)
		put_task_struct(p);

	return ret;
}

static void cleanup_timers_list(struct list_head *head)
{
	struct cpu_timer_list *timer, *next;

	list_for_each_entry_safe(timer, next, head, entry)
		list_del_init(&timer->entry);
}

/*
 * Clean out CPU timers still ticking when a thread exited.  The task
 * pointer is cleared, and the expiry time is replaced with the residual
 * time for later timer_gettime calls to return.
 * This must be called with the siglock held.
 */
static void cleanup_timers(struct list_head *head)
{
	cleanup_timers_list(head);
	cleanup_timers_list(++head);
	cleanup_timers_list(++head);
}

/*
 * These are both called with the siglock held, when the current thread
 * is being reaped.  When the final (leader) thread in the group is reaped,
 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 */
void posix_cpu_timers_exit(struct task_struct *tsk)
{
	add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
						sizeof(unsigned long long));
	cleanup_timers(tsk->cpu_timers);

}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
	cleanup_timers(tsk->signal->cpu_timers);
}

static inline int expires_gt(cputime_t expires, cputime_t new_exp)
{
	return expires == 0 || expires > new_exp;
}

/*
 * Insert the timer on the appropriate list before any timers that
 * expire later.  This must be called with the sighand lock held.
 */
static void arm_timer(struct k_itimer *timer)
{
	struct task_struct *p = timer->it.cpu.task;
	struct list_head *head, *listpos;
	struct task_cputime *cputime_expires;
	struct cpu_timer_list *const nt = &timer->it.cpu;
	struct cpu_timer_list *next;

	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		head = p->cpu_timers;
		cputime_expires = &p->cputime_expires;
	} else {
		head = p->signal->cpu_timers;
		cputime_expires = &p->signal->cputime_expires;
	}
	head += CPUCLOCK_WHICH(timer->it_clock);

	listpos = head;
	list_for_each_entry(next, head, entry) {
		if (nt->expires < next->expires)
			break;
		listpos = &next->entry;
	}
	list_add(&nt->entry, listpos);

	if (listpos == head) {
		unsigned long long exp = nt->expires;

		/*
		 * We are the new earliest-expiring POSIX 1.b timer, hence
		 * need to update expiration cache. Take into account that
		 * for process timers we share expiration cache with itimers
		 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
		 */

		switch (CPUCLOCK_WHICH(timer->it_clock)) {
		case CPUCLOCK_PROF:
			if (expires_gt(cputime_expires->prof_exp, expires_to_cputime(exp)))
				cputime_expires->prof_exp = expires_to_cputime(exp);
			break;
		case CPUCLOCK_VIRT:
			if (expires_gt(cputime_expires->virt_exp, expires_to_cputime(exp)))
				cputime_expires->virt_exp = expires_to_cputime(exp);
			break;
		case CPUCLOCK_SCHED:
			if (cputime_expires->sched_exp == 0 ||
			    cputime_expires->sched_exp > exp)
				cputime_expires->sched_exp = exp;
			break;
		}
	}
}

/*
 * The timer is locked, fire it and arrange for its reload.
 */
static void cpu_timer_fire(struct k_itimer *timer)
{
	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
		/*
		 * User don't want any signal.
		 */
		timer->it.cpu.expires = 0;
	} else if (unlikely(timer->sigq == NULL)) {
		/*
		 * This a special case for clock_nanosleep,
		 * not a normal timer from sys_timer_create.
		 */
		wake_up_process(timer->it_process);
		timer->it.cpu.expires = 0;
	} else if (timer->it.cpu.incr == 0) {
		/*
		 * One-shot timer.  Clear it as soon as it's fired.
		 */
		posix_timer_event(timer, 0);
		timer->it.cpu.expires = 0;
	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
		/*
		 * The signal did not get queued because the signal
		 * was ignored, so we won't get any callback to
		 * reload the timer.  But we need to keep it
		 * ticking in case the signal is deliverable next time.
		 */
		posix_cpu_timer_schedule(timer);
	}
}

/*
 * Sample a process (thread group) timer for the given group_leader task.
 * Must be called with task sighand lock held for safe while_each_thread()
 * traversal.
 */
static int cpu_timer_sample_group(const clockid_t which_clock,
				  struct task_struct *p,
				  unsigned long long *sample)
{
	struct task_cputime cputime;

	thread_group_cputimer(p, &cputime);
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		*sample = cputime_to_expires(cputime.utime + cputime.stime);
		break;
	case CPUCLOCK_VIRT:
		*sample = cputime_to_expires(cputime.utime);
		break;
	case CPUCLOCK_SCHED:
		*sample = cputime.sum_exec_runtime;
		break;
	}
	return 0;
}

#ifdef CONFIG_NO_HZ_FULL
static void nohz_kick_work_fn(struct work_struct *work)
{
	tick_nohz_full_kick_all();
}

static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn);

/*
 * We need the IPIs to be sent from sane process context.
 * The posix cpu timers are always set with irqs disabled.
 */
static void posix_cpu_timer_kick_nohz(void)
{
	if (context_tracking_is_enabled())
		schedule_work(&nohz_kick_work);
}

bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
{
	if (!task_cputime_zero(&tsk->cputime_expires))
		return false;

	/* Check if cputimer is running. This is accessed without locking. */
	if (READ_ONCE(tsk->signal->cputimer.running))
		return false;

	return true;
}
#else
static inline void posix_cpu_timer_kick_nohz(void) { }
#endif

/*
 * Guts of sys_timer_settime for CPU timers.
 * This is called with the timer locked and interrupts disabled.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
			       struct itimerspec *new, struct itimerspec *old)
{
	unsigned long flags;
	struct sighand_struct *sighand;
	struct task_struct *p = timer->it.cpu.task;
	unsigned long long old_expires, new_expires, old_incr, val;
	int ret;

	WARN_ON_ONCE(p == NULL);

	new_expires = timespec_to_sample(timer->it_clock, &new->it_value);

	/*
	 * Protect against sighand release/switch in exit/exec and p->cpu_timers
	 * and p->signal->cpu_timers read/write in arm_timer()
	 */
	sighand = lock_task_sighand(p, &flags);
	/*
	 * If p has just been reaped, we can no
	 * longer get any information about it at all.
	 */
	if (unlikely(sighand == NULL)) {
		return -ESRCH;
	}

	/*
	 * Disarm any old timer after extracting its expiry time.
	 */
	WARN_ON_ONCE(!irqs_disabled());

	ret = 0;
	old_incr = timer->it.cpu.incr;
	old_expires = timer->it.cpu.expires;
	if (unlikely(timer->it.cpu.firing)) {
		timer->it.cpu.firing = -1;
		ret = TIMER_RETRY;
	} else
		list_del_init(&timer->it.cpu.entry);

	/*
	 * We need to sample the current value to convert the new
	 * value from to relative and absolute, and to convert the
	 * old value from absolute to relative.  To set a process
	 * timer, we need a sample to balance the thread expiry
	 * times (in arm_timer).  With an absolute time, we must
	 * check if it's already passed.  In short, we need a sample.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &val);
	} else {
		cpu_timer_sample_group(timer->it_clock, p, &val);
	}

	if (old) {
		if (old_expires == 0) {
			old->it_value.tv_sec = 0;
			old->it_value.tv_nsec = 0;
		} else {
			/*
			 * Update the timer in case it has
			 * overrun already.  If it has,
			 * we'll report it as having overrun
			 * and with the next reloaded timer
			 * already ticking, though we are
			 * swallowing that pending
			 * notification here to install the
			 * new setting.
			 */
			bump_cpu_timer(timer, val);
			if (val < timer->it.cpu.expires) {
				old_expires = timer->it.cpu.expires - val;
				sample_to_timespec(timer->it_clock,
						   old_expires,
						   &old->it_value);
			} else {
				old->it_value.tv_nsec = 1;
				old->it_value.tv_sec = 0;
			}
		}
	}

	if (unlikely(ret)) {
		/*
		 * We are colliding with the timer actually firing.
		 * Punt after filling in the timer's old value, and
		 * disable this firing since we are already reporting
		 * it as an overrun (thanks to bump_cpu_timer above).
		 */
		unlock_task_sighand(p, &flags);
		goto out;
	}

	if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
		new_expires += val;
	}

	/*
	 * Install the new expiry time (or zero).
	 * For a timer with no notification action, we don't actually
	 * arm the timer (we'll just fake it for timer_gettime).
	 */
	timer->it.cpu.expires = new_expires;
	if (new_expires != 0 && val < new_expires) {
		arm_timer(timer);
	}

	unlock_task_sighand(p, &flags);
	/*
	 * Install the new reload setting, and
	 * set up the signal and overrun bookkeeping.
	 */
	timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
						&new->it_interval);

	/*
	 * This acts as a modification timestamp for the timer,
	 * so any automatic reload attempt will punt on seeing
	 * that we have reset the timer manually.
	 */
	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
		~REQUEUE_PENDING;
	timer->it_overrun_last = 0;
	timer->it_overrun = -1;

	if (new_expires != 0 && !(val < new_expires)) {
		/*
		 * The designated time already passed, so we notify
		 * immediately, even if the thread never runs to
		 * accumulate more time on this clock.
		 */
		cpu_timer_fire(timer);
	}

	ret = 0;
 out:
	if (old) {
		sample_to_timespec(timer->it_clock,
				   old_incr, &old->it_interval);
	}
	if (!ret)
		posix_cpu_timer_kick_nohz();
	return ret;
}

static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
{
	unsigned long long now;
	struct task_struct *p = timer->it.cpu.task;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Easy part: convert the reload time.
	 */
	sample_to_timespec(timer->it_clock,
			   timer->it.cpu.incr, &itp->it_interval);

	if (timer->it.cpu.expires == 0) {	/* Timer not armed at all.  */
		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
		return;
	}

	/*
	 * Sample the clock to take the difference with the expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
	} else {
		struct sighand_struct *sighand;
		unsigned long flags;

		/*
		 * Protect against sighand release/switch in exit/exec and
		 * also make timer sampling safe if it ends up calling
		 * thread_group_cputime().
		 */
		sighand = lock_task_sighand(p, &flags);
		if (unlikely(sighand == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 * Call the timer disarmed, nothing else to do.
			 */
			timer->it.cpu.expires = 0;
			sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
					   &itp->it_value);
		} else {
			cpu_timer_sample_group(timer->it_clock, p, &now);
			unlock_task_sighand(p, &flags);
		}
	}

	if (now < timer->it.cpu.expires) {
		sample_to_timespec(timer->it_clock,
				   timer->it.cpu.expires - now,
				   &itp->it_value);
	} else {
		/*
		 * The timer should have expired already, but the firing
		 * hasn't taken place yet.  Say it's just about to expire.
		 */
		itp->it_value.tv_nsec = 1;
		itp->it_value.tv_sec = 0;
	}
}

static unsigned long long
check_timers_list(struct list_head *timers,
		  struct list_head *firing,
		  unsigned long long curr)
{
	int maxfire = 20;

	while (!list_empty(timers)) {
		struct cpu_timer_list *t;

		t = list_first_entry(timers, struct cpu_timer_list, entry);

		if (!--maxfire || curr < t->expires)
			return t->expires;

		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	return 0;
}

/*
 * Check for any per-thread CPU timers that have fired and move them off
 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 */
static void check_thread_timers(struct task_struct *tsk,
				struct list_head *firing)
{
	struct list_head *timers = tsk->cpu_timers;
	struct signal_struct *const sig = tsk->signal;
	struct task_cputime *tsk_expires = &tsk->cputime_expires;
	unsigned long long expires;
	unsigned long soft;

	expires = check_timers_list(timers, firing, prof_ticks(tsk));
	tsk_expires->prof_exp = expires_to_cputime(expires);

	expires = check_timers_list(++timers, firing, virt_ticks(tsk));
	tsk_expires->virt_exp = expires_to_cputime(expires);

	tsk_expires->sched_exp = check_timers_list(++timers, firing,
						   tsk->se.sum_exec_runtime);

	/*
	 * Check for the special case thread timers.
	 */
	soft = READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
	if (soft != RLIM_INFINITY) {
		unsigned long hard =
			READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);

		if (hard != RLIM_INFINITY &&
		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			if (soft < hard) {
				soft += USEC_PER_SEC;
				sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
			}
			printk(KERN_INFO
				"RT Watchdog Timeout: %s[%d]\n",
				tsk->comm, task_pid_nr(tsk));
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
		}
	}
}

static inline void stop_process_timers(struct signal_struct *sig)
{
	struct thread_group_cputimer *cputimer = &sig->cputimer;

	/* Turn off cputimer->running. This is done without locking. */
	WRITE_ONCE(cputimer->running, 0);
}

static u32 onecputick;

static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
			     unsigned long long *expires,
			     unsigned long long cur_time, int signo)
{
	if (!it->expires)
		return;

	if (cur_time >= it->expires) {
		if (it->incr) {
			it->expires += it->incr;
			it->error += it->incr_error;
			if (it->error >= onecputick) {
				it->expires -= cputime_one_jiffy;
				it->error -= onecputick;
			}
		} else {
			it->expires = 0;
		}

		trace_itimer_expire(signo == SIGPROF ?
				    ITIMER_PROF : ITIMER_VIRTUAL,
				    tsk->signal->leader_pid, cur_time);
		__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
	}

	if (it->expires && (!*expires || it->expires < *expires)) {
		*expires = it->expires;
	}
}

/*
 * Check for any per-thread CPU timers that have fired and move them
 * off the tsk->*_timers list onto the firing list.  Per-thread timers
 * have already been taken off.
 */
static void check_process_timers(struct task_struct *tsk,
				 struct list_head *firing)
{
	struct signal_struct *const sig = tsk->signal;
	unsigned long long utime, ptime, virt_expires, prof_expires;
	unsigned long long sum_sched_runtime, sched_expires;
	struct list_head *timers = sig->cpu_timers;
	struct task_cputime cputime;
	unsigned long soft;

	/*
	 * Collect the current process totals.
	 */
	thread_group_cputimer(tsk, &cputime);
	utime = cputime_to_expires(cputime.utime);
	ptime = utime + cputime_to_expires(cputime.stime);
	sum_sched_runtime = cputime.sum_exec_runtime;

	prof_expires = check_timers_list(timers, firing, ptime);
	virt_expires = check_timers_list(++timers, firing, utime);
	sched_expires = check_timers_list(++timers, firing, sum_sched_runtime);

	/*
	 * Check for the special case process timers.
	 */
	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
			 SIGPROF);
	check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
			 SIGVTALRM);
	soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
	if (soft != RLIM_INFINITY) {
		unsigned long psecs = cputime_to_secs(ptime);
		unsigned long hard =
			READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
		cputime_t x;
		if (psecs >= hard) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (psecs >= soft) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
			if (soft < hard) {
				soft++;
				sig->rlim[RLIMIT_CPU].rlim_cur = soft;
			}
		}
		x = secs_to_cputime(soft);
		if (!prof_expires || x < prof_expires) {
			prof_expires = x;
		}
	}

	sig->cputime_expires.prof_exp = expires_to_cputime(prof_expires);
	sig->cputime_expires.virt_exp = expires_to_cputime(virt_expires);
	sig->cputime_expires.sched_exp = sched_expires;
	if (task_cputime_zero(&sig->cputime_expires))
		stop_process_timers(sig);
}

/*
 * This is called from the signal code (via do_schedule_next_timer)
 * when the last timer signal was delivered and we have to reload the timer.
 */
void posix_cpu_timer_schedule(struct k_itimer *timer)
{
	struct sighand_struct *sighand;
	unsigned long flags;
	struct task_struct *p = timer->it.cpu.task;
	unsigned long long now;

	WARN_ON_ONCE(p == NULL);

	/*
	 * Fetch the current sample and update the timer's expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		if (unlikely(p->exit_state))
			goto out;

		/* Protect timer list r/w in arm_timer() */
		sighand = lock_task_sighand(p, &flags);
		if (!sighand)
			goto out;
	} else {
		/*
		 * Protect arm_timer() and timer sampling in case of call to
		 * thread_group_cputime().
		 */
		sighand = lock_task_sighand(p, &flags);
		if (unlikely(sighand == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 */
			timer->it.cpu.expires = 0;
			goto out;
		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
			unlock_task_sighand(p, &flags);
			/* Optimizations: if the process is dying, no need to rearm */
			goto out;
		}
		cpu_timer_sample_group(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		/* Leave the sighand locked for the call below.  */
	}

	/*
	 * Now re-arm for the new expiry time.
	 */
	WARN_ON_ONCE(!irqs_disabled());
	arm_timer(timer);
	unlock_task_sighand(p, &flags);

	/* Kick full dynticks CPUs in case they need to tick on the new timer */
	posix_cpu_timer_kick_nohz();
out:
	timer->it_overrun_last = timer->it_overrun;
	timer->it_overrun = -1;
	++timer->it_requeue_pending;
}

/**
 * task_cputime_expired - Compare two task_cputime entities.
 *
 * @sample:	The task_cputime structure to be checked for expiration.
 * @expires:	Expiration times, against which @sample will be checked.
 *
 * Checks @sample against @expires to see if any field of @sample has expired.
 * Returns true if any field of the former is greater than the corresponding
 * field of the latter if the latter field is set.  Otherwise returns false.
 */
static inline int task_cputime_expired(const struct task_cputime *sample,
					const struct task_cputime *expires)
{
	if (expires->utime && sample->utime >= expires->utime)
		return 1;
	if (expires->stime && sample->utime + sample->stime >= expires->stime)
		return 1;
	if (expires->sum_exec_runtime != 0 &&
	    sample->sum_exec_runtime >= expires->sum_exec_runtime)
		return 1;
	return 0;
}

/**
 * fastpath_timer_check - POSIX CPU timers fast path.
 *
 * @tsk:	The task (thread) being checked.
 *
 * Check the task and thread group timers.  If both are zero (there are no
 * timers set) return false.  Otherwise snapshot the task and thread group
 * timers and compare them with the corresponding expiration times.  Return
 * true if a timer has expired, else return false.
 */
static inline int fastpath_timer_check(struct task_struct *tsk)
{
	struct signal_struct *sig;

	if (!task_cputime_zero(&tsk->cputime_expires)) {
		struct task_cputime task_sample;

		task_cputime(tsk, &task_sample.utime, &task_sample.stime);
		task_sample.sum_exec_runtime = tsk->se.sum_exec_runtime;
		if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
			return 1;
	}

	sig = tsk->signal;
	/* Check if cputimer is running. This is accessed without locking. */
	if (READ_ONCE(sig->cputimer.running)) {
		struct task_cputime group_sample;

		sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);

		if (task_cputime_expired(&group_sample, &sig->cputime_expires))
{'fraction_non_alphanumeric': 0.11236892473294181, 'fraction_numerical': 0.002911874887532922, 'mean_word_length': 3.891573977754661, 'pattern_counts': {'":': 0, '<': 59, '<?xml version=': 0, '>': 495, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '6790389', 'n_tokens_mistral': 24399, 'n_tokens_neox': 22288, 'n_words': 5888}