- 根目录:
- kernel
- time
- 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>
#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, true);
}
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;
/*
* If cputime_expires is zero, then there are no active
* per thread CPU timers.
*/
if (task_cputime_zero(&tsk->cputime_expires))
return;
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, false);
}
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;
/*
* If cputimer is not running, then there are no active
* process wide timers (POSIX 1.b, itimers, RLIMIT_CPU).
*/
if (!READ_ONCE(tsk->signal->cputimer.running))
return;
/*
* Signify that a thread is checking for process timers.
* Write access to this field is protected by the sighand lock.
*/
sig->cputimer.checking_timer = true;
/*
* 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);
sig->cputimer.checking_timer = false;
}
/*
* 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 thread group timers expired when the cputimer is
* running and no other thread in the group is already checking
* for thread group cputimers. These fields are read without the
* sighand lock. However, this is fine because this is meant to
* be a fastpath heuristic to determine whether we should try to
* acquire the sighand lock to check/handle timers.
*
* In the worst case scenario, if 'running' or 'checking_timer' gets
* set but the current thread doesn't see the change yet, we'll wait
* until the next thread in the group gets a scheduler interrupt to
* handle the timer. This isn't an issue in practice because these
* types of delays with signals actually getting sent are expected.
*/
if (READ_ONCE(sig->cputimer.running) &&
!READ_ONCE(sig->cputimer.checking_timer)) {
struct task_cputime group_sample;
sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);
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;
unsigned long flags;
WARN_ON_ONCE(!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;
if (!lock_task_sighand(tsk, &flags))
return;
/*
* 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);
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.
*/
unlock_task_sighand(tsk, &flags);
/*
* Now that all the timers on our list have the firing flag,
* no one 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)
{
unsigned long long now;
WARN_ON_ONCE(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 (*oldval) {
if (*oldval <= now) {
/* Just about to fire. */
*oldval = cputime_one_jiffy;
} else {
*oldval -= now;
}
}
if (!*newval)
goto out;
*newval += now;
}
/*
* 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;
}
out:
posix_cpu_timer_kick_nohz();
}
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 == 0) {
/*
* Our timer fired and was reset, below
* deletion can not fail.
*/
posix_cpu_timer_del(&timer);
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);
error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
if (!error) {
/*
* Timer is now unarmed, deletion can not fail.
*/
posix_cpu_timer_del(&timer);
}
spin_unlock_irq(&timer.it_lock);
while (error == TIMER_RETRY) {
/*
* We need to handle case when timer was or is in the
* middle of firing. In other cases we already freed
* resources.
*/
spin_lock_irq(&timer.it_lock);
error = posix_cpu_timer_del(&timer);
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;
}
static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
struct timespec *rqtp, struct timespec __user *rmtp)
{
struct restart_block *restart_block = ¤t->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 && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
return -EFAULT;
restart_block->fn = posix_cpu_nsleep_restart;
restart_block->nanosleep.clockid = which_clock;
restart_block->nanosleep.rmtp = rmtp;
restart_block->nanosleep.expires = timespec_to_ns(rqtp);
}
return error;
}
static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
{
clockid_t which_clock = restart_block->nanosleep.clockid;
struct timespec t;
struct itimerspec it;
int error;
t = ns_to_timespec(restart_block->nanosleep.expires);
error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
if (error == -ERESTART_RESTARTBLOCK) {
struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
/*
* Report back to the user the time still remaining.
*/
if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
return -EFAULT;
restart_block->nanosleep.expires = timespec_to_ns(&t);
}
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);
}
struct k_clock clock_posix_cpu = {
.clock_getres = posix_cpu_clock_getres,
.clock_set = posix_cpu_clock_set,
.clock_get = posix_cpu_clock_get,
.timer_create = posix_cpu_timer_create,
.nsleep = posix_cpu_nsleep,
.nsleep_restart = posix_cpu_nsleep_restart,
.timer_set = posix_cpu_timer_set,
.timer_del = posix_cpu_timer_del,
.timer_get = posix_cpu_timer_get,
};
static __init int init_posix_cpu_timers(void)
{
struct k_clock process = {
.clock_getres = process_cpu_clock_getres,
.clock_get = process_cpu_clock_get,
.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,
.timer_create = thread_cpu_timer_create,
};
struct timespec ts;
posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
posix_timers_register_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);