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/*
* 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>

/*
* 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(unsigned long rlim_new)
{
cputime_t cputime = secs_to_cputime(rlim_new);

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

read_lock(&tasklist_lock);
p = find_task_by_vpid(pid);
if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
same_thread_group(p, current) : thread_group_leader(p))) {
error = -EINVAL;
}
read_unlock(&tasklist_lock);

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 cputime_lt(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 = cputime_add(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 = cputime_sub(a.cpu, b.cpu);
}
return a;
}

/*
* Divide and limit the result to res >= 1
*
* This is necessary to prevent signal delivery starvation, when the result of
* the division would be rounded down to 0.
*/
static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
{
cputime_t res = cputime_div(time, div);

return max_t(cputime_t, res, 1);
}

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

static inline cputime_t prof_ticks(struct task_struct *p)
{
return cputime_add(p->utime, p->stime);
}
static inline cputime_t virt_ticks(struct task_struct *p)
{
return p->utime;
}

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;
}

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;
}

void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
{
struct sighand_struct *sighand;
struct signal_struct *sig;
struct task_struct *t;

*times = INIT_CPUTIME;

rcu_read_lock();
sighand = rcu_dereference(tsk->sighand);
if (!sighand)
goto out;

sig = tsk->signal;

t = tsk;
do {
times->utime = cputime_add(times->utime, t->utime);
times->stime = cputime_add(times->stime, t->stime);
times->sum_exec_runtime += t->se.sum_exec_runtime;

t = next_thread(t);
} while (t != tsk);

times->utime = cputime_add(times->utime, sig->utime);
times->stime = cputime_add(times->stime, sig->stime);
times->sum_exec_runtime += sig->sum_sched_runtime;
out:
rcu_read_unlock();
}

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

if (cputime_gt(b->stime, a->stime))
a->stime = b->stime;

if (b->sum_exec_runtime > a->sum_exec_runtime)
a->sum_exec_runtime = b->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;
unsigned long flags;

spin_lock_irqsave(&cputimer->lock, flags);
if (!cputimer->running) {
cputimer->running = 1;
/*
* 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, &sum);
}
*times = cputimer->cputime;
spin_unlock_irqrestore(&cputimer->lock, flags);
}

/*
* Sample a process (thread group) clock for the given group_leader task.
* Must be called with tasklist_lock held for reading.
*/
static int cpu_clock_sample_group(const clockid_t which_clock,
struct task_struct *p,
union cpu_time_count *cpu)
{
struct task_cputime cputime;

switch (CPUCLOCK_WHICH(which_clock)) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
thread_group_cputime(p, &cputime);
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
thread_group_cputime(p, &cputime);
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
cpu->sched = thread_group_sched_runtime(p);
break;
}
return 0;
}


int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
const pid_t pid = CPUCLOCK_PID(which_clock);
int error = -EINVAL;
union cpu_time_count 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;
}


/*
* 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.
*/
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);

read_lock(&tasklist_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 && !thread_group_leader(p))
p = NULL;
}
}
new_timer->it.cpu.task = p;
if (p) {
get_task_struct(p);
} else {
ret = -EINVAL;
}
read_unlock(&tasklist_lock);

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.)
*/
int posix_cpu_timer_del(struct k_itimer *timer)
{
struct task_struct *p = timer->it.cpu.task;
int ret = 0;

if (likely(p != NULL)) {
read_lock(&tasklist_lock);
if (unlikely(p->sighand == NULL)) {
/*
* We raced with the reaping of the task.
* The deletion should have cleared us off the list.
*/
BUG_ON(!list_empty(&timer->it.cpu.entry));
} else {
spin_lock(&p->sighand->siglock);
if (timer->it.cpu.firing)
ret = TIMER_RETRY;
else
list_del(&timer->it.cpu.entry);
spin_unlock(&p->sighand->siglock);
}
read_unlock(&tasklist_lock);

if (!ret)
put_task_struct(p);
}

return ret;
}

/*
* 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,
cputime_t utime, cputime_t stime,
unsigned long long sum_exec_runtime)
{
struct cpu_timer_list *timer, *next;
cputime_t ptime = cputime_add(utime, stime);

list_for_each_entry_safe(timer, next, head, entry) {
list_del_init(&timer->entry);
if (cputime_lt(timer->expires.cpu, ptime)) {
timer->expires.cpu = cputime_zero;
} else {
timer->expires.cpu = cputime_sub(timer->expires.cpu,
ptime);
}
}

++head;
list_for_each_entry_safe(timer, next, head, entry) {
list_del_init(&timer->entry);
if (cputime_lt(timer->expires.cpu, utime)) {
timer->expires.cpu = cputime_zero;
} else {
timer->expires.cpu = cputime_sub(timer->expires.cpu,
utime);
}
}

++head;
list_for_each_entry_safe(timer, next, head, entry) {
list_del_init(&timer->entry);
if (timer->expires.sched < sum_exec_runtime) {
timer->expires.sched = 0;
} else {
timer->expires.sched -= sum_exec_runtime;
}
}
}

/*
* 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)
{
cleanup_timers(tsk->cpu_timers,
tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);

}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
struct signal_struct *const sig = tsk->signal;

cleanup_timers(tsk->signal->cpu_timers,
cputime_add(tsk->utime, sig->utime),
cputime_add(tsk->stime, sig->stime),
tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
}

static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
{
/*
* That's all for this thread or process.
* We leave our residual in expires to be reported.
*/
put_task_struct(timer->it.cpu.task);
timer->it.cpu.task = NULL;
timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
timer->it.cpu.expires,
now);
}

static inline int expires_gt(cputime_t expires, cputime_t new_exp)
{
return cputime_eq(expires, cputime_zero) ||
cputime_gt(expires, new_exp);
}

/*
* Insert the timer on the appropriate list before any timers that
* expire later. This must be called with the tasklist_lock held
* for reading, interrupts disabled and p->sighand->siglock taken.
*/
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 (cpu_time_before(timer->it_clock, nt->expires, next->expires))
break;
listpos = &next->entry;
}
list_add(&nt->entry, listpos);

if (listpos == head) {
union cpu_time_count *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, exp->cpu))
cputime_expires->prof_exp = exp->cpu;
break;
case CPUCLOCK_VIRT:
if (expires_gt(cputime_expires->virt_exp, exp->cpu))
cputime_expires->virt_exp = exp->cpu;
break;
case CPUCLOCK_SCHED:
if (cputime_expires->sched_exp == 0 ||
cputime_expires->sched_exp > exp->sched)
cputime_expires->sched_exp = exp->sched;
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.sched = 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.sched = 0;
} else if (timer->it.cpu.incr.sched == 0) {
/*
* One-shot timer. Clear it as soon as it's fired.
*/
posix_timer_event(timer, 0);
timer->it.cpu.expires.sched = 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 tasklist_lock held for reading.
*/
static int cpu_timer_sample_group(const clockid_t which_clock,
struct task_struct *p,
union cpu_time_count *cpu)
{
struct task_cputime cputime;

thread_group_cputimer(p, &cputime);
switch (CPUCLOCK_WHICH(which_clock)) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
}

/*
* 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.)
*/
int posix_cpu_timer_set(struct k_itimer *timer, int flags,
struct itimerspec *new, struct itimerspec *old)
{
struct task_struct *p = timer->it.cpu.task;
union cpu_time_count old_expires, new_expires, old_incr, val;
int ret;

if (unlikely(p == NULL)) {
/*
* Timer refers to a dead task's clock.
*/
return -ESRCH;
}

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

read_lock(&tasklist_lock);
/*
* We need the tasklist_lock to protect against reaping that
* clears p->sighand. If p has just been reaped, we can no
* longer get any information about it at all.
*/
if (unlikely(p->sighand == NULL)) {
read_unlock(&tasklist_lock);
put_task_struct(p);
timer->it.cpu.task = NULL;
return -ESRCH;
}

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

ret = 0;
old_incr = timer->it.cpu.incr;
spin_lock(&p->sighand->siglock);
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.sched == 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 (cpu_time_before(timer->it_clock, val,
timer->it.cpu.expires)) {
old_expires = cpu_time_sub(
timer->it_clock,
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).
*/
spin_unlock(&p->sighand->siglock);
read_unlock(&tasklist_lock);
goto out;
}

if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
cpu_time_add(timer->it_clock, &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.sched != 0 &&
cpu_time_before(timer->it_clock, val, new_expires)) {
arm_timer(timer);
}

spin_unlock(&p->sighand->siglock);
read_unlock(&tasklist_lock);

/*
* 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.sched != 0 &&
!cpu_time_before(timer->it_clock, 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);
}
return ret;
}

void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
{
union cpu_time_count now;
struct task_struct *p = timer->it.cpu.task;
int clear_dead;

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

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

if (unlikely(p == NULL)) {
/*
* This task already died and the timer will never fire.
* In this case, expires is actually the dead value.
*/
dead:
sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
&itp->it_value);
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);
clear_dead = p->exit_state;
} else {
read_lock(&tasklist_lock);
if (unlikely(p->sighand == NULL)) {
/*
* The process has been reaped.
* We can't even collect a sample any more.
* Call the timer disarmed, nothing else to do.
*/
put_task_struct(p);
timer->it.cpu.task = NULL;
timer->it.cpu.expires.sched = 0;
read_unlock(&tasklist_lock);
goto dead;
} else {
cpu_timer_sample_group(timer->it_clock, p, &now);
clear_dead = (unlikely(p->exit_state) &&
thread_group_empty(p));
}
read_unlock(&tasklist_lock);
}

if (unlikely(clear_dead)) {
/*
* We've noticed that the thread is dead, but
* not yet reaped. Take this opportunity to
* drop our task ref.
*/
clear_dead_task(timer, now);
goto dead;
}

if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
sample_to_timespec(timer->it_clock,
cpu_time_sub(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;
}
}

/*
* 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)
{
int maxfire;
struct list_head *timers = tsk->cpu_timers;
struct signal_struct *const sig = tsk->signal;
unsigned long soft;

maxfire = 20;
tsk->cputime_expires.prof_exp = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
tsk->cputime_expires.prof_exp = t->expires.cpu;
break;
}
t->firing = 1;
list_move_tail(&t->entry, firing);
}

++timers;
maxfire = 20;
tsk->cputime_expires.virt_exp = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
tsk->cputime_expires.virt_exp = t->expires.cpu;
break;
}
t->firing = 1;
list_move_tail(&t->entry, firing);
}

++timers;
maxfire = 20;
tsk->cputime_expires.sched_exp = 0;
while (!list_empty(timers)) {
struct cpu_timer_list *t = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
tsk->cputime_expires.sched_exp = t->expires.sched;
break;
}
t->firing = 1;
list_move_tail(&t->entry, firing);
}

/*
* Check for the special case thread timers.
*/
soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long hard =
ACCESS_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 void stop_process_timers(struct signal_struct *sig)
{
struct thread_group_cputimer *cputimer = &sig->cputimer;
unsigned long flags;

spin_lock_irqsave(&cputimer->lock, flags);
cputimer->running = 0;
spin_unlock_irqrestore(&cputimer->lock, flags);
}

static u32 onecputick;

static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
cputime_t *expires, cputime_t cur_time, int signo)
{
if (cputime_eq(it->expires, cputime_zero))
return;

if (cputime_ge(cur_time, it->expires)) {
if (!cputime_eq(it->incr, cputime_zero)) {
it->expires = cputime_add(it->expires, it->incr);
it->error += it->incr_error;
if (it->error >= onecputick) {
it->expires = cputime_sub(it->expires,
cputime_one_jiffy);
it->error -= onecputick;
}
} else {
it->expires = cputime_zero;
}

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 (!cputime_eq(it->expires, cputime_zero) &&
(cputime_eq(*expires, cputime_zero) ||
cputime_lt(it->expires, *expires))) {
*expires = it->expires;
}
}

/**
* 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_eq(cputime->utime, cputime_zero) &&
cputime_eq(cputime->stime, cputime_zero) &&
cputime->sum_exec_runtime == 0)
return 1;
return 0;
}

/*
* 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)
{
int maxfire;
struct signal_struct *const sig = tsk->signal;
cputime_t 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.utime;
ptime = cputime_add(utime, cputime.stime);
sum_sched_runtime = cputime.sum_exec_runtime;
maxfire = 20;
prof_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *tl = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
prof_expires = tl->expires.cpu;
break;
}
tl->firing = 1;
list_move_tail(&tl->entry, firing);
}

++timers;
maxfire = 20;
virt_expires = cputime_zero;
while (!list_empty(timers)) {
struct cpu_timer_list *tl = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
virt_expires = tl->expires.cpu;
break;
}
tl->firing = 1;
list_move_tail(&tl->entry, firing);
}

++timers;
maxfire = 20;
sched_expires = 0;
while (!list_empty(timers)) {
struct cpu_timer_list *tl = list_first_entry(timers,
struct cpu_timer_list,
entry);
if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
sched_expires = tl->expires.sched;
break;
}
tl->firing = 1;
list_move_tail(&tl->entry, firing);
}

/*
* 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 = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long psecs = cputime_to_secs(ptime);
unsigned long hard =
ACCESS_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 (cputime_eq(prof_expires, cputime_zero) ||
cputime_lt(x, prof_expires)) {
prof_expires = x;
}
}

sig->cputime_expires.prof_exp = prof_expires;
sig->cputime_expires.virt_exp = 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 task_struct *p = timer->it.cpu.task;
union cpu_time_count now;

if (unlikely(p == NULL))
/*
* The task was cleaned up already, no future firings.
*/
goto out;

/*
* 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)) {
clear_dead_task(timer, now);
goto out;
}
read_lock(&tasklist_lock); /* arm_timer needs it. */
spin_lock(&p->sighand->siglock);
} else {
read_lock(&tasklist_lock);
if (unlikely(p->sighand == NULL)) {
/*
* The process has been reaped.
* We can't even collect a sample any more.
*/
put_task_struct(p);
timer->it.cpu.task = p = NULL;
timer->it.cpu.expires.sched = 0;
goto out_unlock;
} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
/*
* We've noticed that the thread is dead, but
* not yet reaped. Take this opportunity to
* drop our task ref.
*/
clear_dead_task(timer, now);
goto out_unlock;
}
spin_lock(&p->sighand->siglock);
cpu_timer_sample_group(timer->it_clock, p, &now);
bump_cpu_timer(timer, now);
/* Leave the tasklist_lock locked for the call below. */
}

/*
* Now re-arm for the new expiry time.
*/
BUG_ON(!irqs_disabled());
arm_timer(timer);
spin_unlock(&p->sighand->siglock);

out_unlock:
read_unlock(&tasklist_lock);

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 (!cputime_eq(expires->utime, cputime_zero) &&
cputime_ge(sample->utime, expires->utime))
return 1;
if (!cputime_eq(expires->stime, cputime_zero) &&
cputime_ge(cputime_add(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;

/* tsk == current, ensure it is safe to use ->signal/sighand */
if (unlikely(tsk->exit_state))
return 0;

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

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

sig = tsk->signal;
if (sig->cputimer.running) {
struct task_cputime group_sample;

thread_group_cputimer(tsk, &group_sample);
if (task_cputime_expired(&group_sample, &sig->cputime_expires))
return 1;
}

return 0;
}

/*
* This is called from the timer interrupt handler. The irq handler has
* already updated our counts. We need to check if any timers fire now.
* Interrupts are disabled.
*/
void run_posix_cpu_timers(struct task_struct *tsk)
{
LIST_HEAD(firing);
struct k_itimer *timer, *next;

BUG_ON(!irqs_disabled());

/*
* The fast path checks that there are no expired thread or thread
* group timers. If that's so, just return.
*/
if (!fastpath_timer_check(tsk))
return;

spin_lock(&tsk->sighand->siglock);
/*
* Here we take off tsk->signal->cpu_timers[N] and
* tsk->cpu_timers[N] all the timers that are firing, and
* put them on the firing list.
*/
check_thread_timers(tsk, &firing);
/*
* If there are any active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) cputimer must be running.
*/
if (tsk->signal->cputimer.running)
check_process_timers(tsk, &firing);

/*
* We must release these locks before taking any timer's lock.
* There is a potential race with timer deletion here, as the
* siglock now protects our private firing list. We have set
* the firing flag in each timer, so that a deletion attempt
* that gets the timer lock before we do will give it up and
* spin until we've taken care of that timer below.
*/
spin_unlock(&tsk->sighand->siglock);

/*
* Now that all the timers on our list have the firing flag,
* noone will touch their list entries but us. We'll take
* each timer's lock before clearing its firing flag, so no
* timer call will interfere.
*/
list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
int cpu_firing;

spin_lock(&timer->it_lock);
list_del_init(&timer->it.cpu.entry);
cpu_firing = timer->it.cpu.firing;
timer->it.cpu.firing = 0;
/*
* The firing flag is -1 if we collided with a reset
* of the timer, which already reported this
* almost-firing as an overrun. So don't generate an event.
*/
if (likely(cpu_firing >= 0))
cpu_timer_fire(timer);
spin_unlock(&timer->it_lock);
}
}

/*
* Set one of the process-wide special case CPU timers or RLIMIT_CPU.
* The tsk->sighand->siglock must be held by the caller.
*/
void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
cputime_t *newval, cputime_t *oldval)
{
union cpu_time_count now;

BUG_ON(clock_idx == CPUCLOCK_SCHED);
cpu_timer_sample_group(clock_idx, tsk, &now);

if (oldval) {
/*
* We are setting itimer. The *oldval is absolute and we update
* it to be relative, *newval argument is relative and we update
* it to be absolute.
*/
if (!cputime_eq(*oldval, cputime_zero)) {
if (cputime_le(*oldval, now.cpu)) {
/* Just about to fire. */
*oldval = cputime_one_jiffy;
} else {
*oldval = cputime_sub(*oldval, now.cpu);
}
}

if (cputime_eq(*newval, cputime_zero))
return;
*newval = cputime_add(*newval, now.cpu);
}

/*
* Update expiration cache if we are the earliest timer, or eventually
* RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
*/
switch (clock_idx) {
case CPUCLOCK_PROF:
if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
tsk->signal->cputime_expires.prof_exp = *newval;
break;
case CPUCLOCK_VIRT:
if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
tsk->signal->cputime_expires.virt_exp = *newval;
break;
}
}

static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
struct timespec *rqtp, struct itimerspec *it)
{
struct k_itimer timer;
int error;

/*
* Set up a temporary timer and then wait for it to go off.
*/
memset(&timer, 0, sizeof timer);
spin_lock_init(&timer.it_lock);
timer.it_clock = which_clock;
timer.it_overrun = -1;
error = posix_cpu_timer_create(&timer);
timer.it_process = current;
if (!error) {
static struct itimerspec zero_it;

memset(it, 0, sizeof *it);
it->it_value = *rqtp;

spin_lock_irq(&timer.it_lock);
error = posix_cpu_timer_set(&timer, flags, it, NULL);
if (error) {
spin_unlock_irq(&timer.it_lock);
return error;
}

while (!signal_pending(current)) {
if (timer.it.cpu.expires.sched == 0) {
/*
* Our timer fired and was reset.
*/
spin_unlock_irq(&timer.it_lock);
return 0;
}

/*
* Block until cpu_timer_fire (or a signal) wakes us.
*/
__set_current_state(TASK_INTERRUPTIBLE);
spin_unlock_irq(&timer.it_lock);
schedule();
spin_lock_irq(&timer.it_lock);
}

/*
* We were interrupted by a signal.
*/
sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
posix_cpu_timer_set(&timer, 0, &zero_it, it);
spin_unlock_irq(&timer.it_lock);

if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
/*
* It actually did fire already.
*/
return 0;
}

error = -ERESTART_RESTARTBLOCK;
}

return error;
}

int posix_cpu_nsleep(const clockid_t which_clock, int flags,
struct timespec *rqtp, struct timespec __user *rmtp)
{
struct restart_block *restart_block =
&current_thread_info()->restart_block;
struct itimerspec it;
int error;

/*
* Diagnose required errors first.
*/
if (CPUCLOCK_PERTHREAD(which_clock) &&
(CPUCLOCK_PID(which_clock) == 0 ||
CPUCLOCK_PID(which_clock) == current->pid))
return -EINVAL;

error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);

if (error == -ERESTART_RESTARTBLOCK) {

if (flags & TIMER_ABSTIME)
return -ERESTARTNOHAND;
/*
* Report back to the user the time still remaining.
*/
if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
return -EFAULT;

restart_block->fn = posix_cpu_nsleep_restart;
restart_block->arg0 = which_clock;
restart_block->arg1 = (unsigned long) rmtp;
restart_block->arg2 = rqtp->tv_sec;
restart_block->arg3 = rqtp->tv_nsec;
}
return error;
}

long posix_cpu_nsleep_restart(struct restart_block *restart_block)
{
clockid_t which_clock = restart_block->arg0;
struct timespec __user *rmtp;
struct timespec t;
struct itimerspec it;
int error;

rmtp = (struct timespec __user *) restart_block->arg1;
t.tv_sec = restart_block->arg2;
t.tv_nsec = restart_block->arg3;

restart_block->fn = do_no_restart_syscall;
error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);

if (error == -ERESTART_RESTARTBLOCK) {
/*
* Report back to the user the time still remaining.
*/
if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
return -EFAULT;

restart_block->fn = posix_cpu_nsleep_restart;
restart_block->arg0 = which_clock;
restart_block->arg1 = (unsigned long) rmtp;
restart_block->arg2 = t.tv_sec;
restart_block->arg3 = t.tv_nsec;
}
return error;

}


#define PROCESS_CLOCK MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
#define THREAD_CLOCK MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)

static int process_cpu_clock_getres(const clockid_t which_clock,
struct timespec *tp)
{
return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
}
static int process_cpu_clock_get(const clockid_t which_clock,
struct timespec *tp)
{
return posix_cpu_clock_get(PROCESS_CLOCK, tp);
}
static int process_cpu_timer_create(struct k_itimer *timer)
{
timer->it_clock = PROCESS_CLOCK;
return posix_cpu_timer_create(timer);
}
static int process_cpu_nsleep(const clockid_t which_clock, int flags,
struct timespec *rqtp,
struct timespec __user *rmtp)
{
return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
}
static long process_cpu_nsleep_restart(struct restart_block *restart_block)
{
return -EINVAL;
}
static int thread_cpu_clock_getres(const clockid_t which_clock,
struct timespec *tp)
{
return posix_cpu_clock_getres(THREAD_CLOCK, tp);
}
static int thread_cpu_clock_get(const clockid_t which_clock,
struct timespec *tp)
{
return posix_cpu_clock_get(THREAD_CLOCK, tp);
}
static int thread_cpu_timer_create(struct k_itimer *timer)
{
timer->it_clock = THREAD_CLOCK;
return posix_cpu_timer_create(timer);
}
static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
struct timespec *rqtp, struct timespec __user *rmtp)
{
return -EINVAL;
}
static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
{
return -EINVAL;
}

static __init int init_posix_cpu_timers(void)
{
struct k_clock process = {
.clock_getres = process_cpu_clock_getres,
.clock_get = process_cpu_clock_get,
.clock_set = do_posix_clock_nosettime,
.timer_create = process_cpu_timer_create,
.nsleep = process_cpu_nsleep,
.nsleep_restart = process_cpu_nsleep_restart,
};
struct k_clock thread = {
.clock_getres = thread_cpu_clock_getres,
.clock_get = thread_cpu_clock_get,
.clock_set = do_posix_clock_nosettime,
.timer_create = thread_cpu_timer_create,
.nsleep = thread_cpu_nsleep,
.nsleep_restart = thread_cpu_nsleep_restart,
};
struct timespec ts;

register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);

cputime_to_timespec(cputime_one_jiffy, &ts);
onecputick = ts.tv_nsec;
WARN_ON(ts.tv_sec != 0);

return 0;
}
__initcall(init_posix_cpu_timers);
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