path: root/kernel/posix-cpu-timers.c

/*
 * 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>

/*
 * 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 union cpu_time_count
timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
{
	union cpu_time_count ret;
	ret.sched = 0;		/* high half always zero when .cpu used */
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
	} else {
		ret.cpu = timespec_to_cputime(tp);
	}
	return ret;
}

static void sample_to_timespec(const clockid_t which_clock,
			       union cpu_time_count cpu,
			       struct timespec *tp)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
		*tp = ns_to_timespec(cpu.sched);
	else
		cputime_to_timespec(cpu.cpu, tp);
}

static inline int cpu_time_before(const clockid_t which_clock,
				  union cpu_time_count now,
				  union cpu_time_count then)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		return now.sched < then.sched;
	}  else {
		return now.cpu < then.cpu;
	}
}
static inline void cpu_time_add(const clockid_t which_clock,
				union cpu_time_count *acc,
			        union cpu_time_count val)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		acc->sched += val.sched;
	}  else {
		acc->cpu += val.cpu;
	}
}
static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
						union cpu_time_count a,
						union cpu_time_count b)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		a.sched -= b.sched;
	}  else {
		a.cpu -= b.cpu;
	}
	return a;
}

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

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

	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
		unsigned long long delta, incr;

		if (now.sched < timer->it.cpu.expires.sched)
			return;
		incr = timer->it.cpu.incr.sched;
		delta = now.sched + incr - timer->it.cpu.expires.sched;
		/* 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.sched += incr;
			timer->it_overrun += 1 << i;
			delta -= incr;
		}
	} else {
		cputime_t delta, incr;

		if (now.cpu < timer->it.cpu.expires.cpu)
			return;
		incr = timer->it.cpu.incr.cpu;
		delta = now.cpu + incr - timer->it.cpu.expires.cpu;
		/* Don't use (incr*2 < delta), incr*2 might overflow. */
		for (i = 0; incr < delta - incr; i++)
			     incr += incr;
		for (; i >= 0; incr = incr >> 1, i--) {
			if (delta < incr)
				continue;
			timer->it.cpu.expires.cpu += incr;
			timer->it_overrun += 1 << i;
			delta -= incr;
		}
	}
}

static inline cputime_t prof_ticks(struct task_struct *p)
{
	return p->utime + p->stime;
}
static inline cputime_t virt_ticks(struct task_struct *p)
{
	return p->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,
			    union cpu_time_count *cpu)
{
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		cpu->cpu = prof_ticks(p);
		break;
	case CPUCLOCK_VIRT:
		cpu->cpu = virt_ticks(p);
		break;
	case CPUCLOCK_SCHED:
		cpu->sched = task_sched_runtime(p);
		break;
	}
	return 0;
}

static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
{
	if (b->utime > a->utime)
		a->utime = b->utime;

	if (b->stime > a->stime)
		a->stime = b->stime