blob: 3bb96a8b49c9bd8888e1aaa1791470fe169f4a8f [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Implement CPU time clocks for the POSIX clock interface.
*/
#include <linux/sched/signal.h>
#include <linux/sched/cputime.h>
#include <linux/posix-timers.h>
#include <linux/errno.h>
#include <linux/math64.h>
#include <linux/uaccess.h>
#include <linux/kernel_stat.h>
#include <trace/events/timer.h>
#include <linux/tick.h>
#include <linux/workqueue.h>
#include <linux/compat.h>
#include <linux/sched/deadline.h>
#include "posix-timers.h"
static void posix_cpu_timer_rearm(struct k_itimer *timer);
void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
{
posix_cputimers_init(pct);
if (cpu_limit != RLIM_INFINITY) {
pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
pct->timers_active = true;
}
}
/*
* Called after updating RLIMIT_CPU to run cpu timer and update
* tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
* necessary. Needs siglock protection since other code may update the
* expiration cache as well.
*/
void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
{
u64 nsecs = rlim_new * NSEC_PER_SEC;
spin_lock_irq(&task->sighand->siglock);
set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
spin_unlock_irq(&task->sighand->siglock);
}
/*
* Functions for validating access to tasks.
*/
static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
{
const bool thread = !!CPUCLOCK_PERTHREAD(clock);
const pid_t upid = CPUCLOCK_PID(clock);
struct pid *pid;
if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
return NULL;
/*
* If the encoded PID is 0, then the timer is targeted at current
* or the process to which current belongs.
*/
if (upid == 0)
return thread ? task_pid(current) : task_tgid(current);
pid = find_vpid(upid);
if (!pid)
return NULL;
if (thread) {
struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
}
/*
* For clock_gettime(PROCESS) allow finding the process by
* with the pid of the current task. The code needs the tgid
* of the process so that pid_task(pid, PIDTYPE_TGID) can be
* used to find the process.
*/
if (gettime && (pid == task_pid(current)))
return task_tgid(current);
/*
* For processes require that pid identifies a process.
*/
return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
}
static inline int validate_clock_permissions(const clockid_t clock)
{
int ret;
rcu_read_lock();
ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
rcu_read_unlock();
return ret;
}
static inline enum pid_type clock_pid_type(const clockid_t clock)
{
return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
}
static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
{
return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
}
/*
* Update expiry time from increment, and increase overrun count,
* given the current clock sample.
*/
static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
{
u64 delta, incr, expires = timer->it.cpu.node.expires;
int i;
if (!timer->it_interval)
return expires;
if (now < expires)
return expires;
incr = timer->it_interval;
delta = now + incr - 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.node.expires += incr;
timer->it_overrun += 1LL << i;
delta -= incr;
}
return timer->it.cpu.node.expires;
}
/* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
{
return !(~pct->bases[CPUCLOCK_PROF].nextevt |
~pct->bases[CPUCLOCK_VIRT].nextevt |
~pct->bases[CPUCLOCK_SCHED].nextevt);
}
static int
posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
{
int error = validate_clock_permissions(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 clock, const struct timespec64 *tp)
{
int error = validate_clock_permissions(clock);
/*
* You can never reset a CPU clock, but we check for other errors
* in the call before failing with EPERM.
*/
return error ? : -EPERM;
}
/*
* Sample a per-thread clock for the given task. clkid is validated.
*/
static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
{
u64 utime, stime;
if (clkid == CPUCLOCK_SCHED)
return task_sched_runtime(p);
task_cputime(p, &utime, &stime);
switch (clkid) {
case CPUCLOCK_PROF:
return utime + stime;
case CPUCLOCK_VIRT:
return utime;
default:
WARN_ON_ONCE(1);
}
return 0;
}
static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
{
samples[CPUCLOCK_PROF] = stime + utime;
samples[CPUCLOCK_VIRT] = utime;
samples[CPUCLOCK_SCHED] = rtime;
}
static void task_sample_cputime(struct task_struct *p, u64 *samples)
{
u64 stime, utime;
task_cputime(p, &utime, &stime);
store_samples(samples, stime, utime, p->se.sum_exec_runtime);
}
static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
u64 *samples)
{
u64 stime, utime, rtime;
utime = atomic64_read(&at->utime);
stime = atomic64_read(&at->stime);
rtime = atomic64_read(&at->sum_exec_runtime);
store_samples(samples, stime, utime, rtime);
}
/*
* 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);
}
/**
* thread_group_sample_cputime - Sample cputime for a given task
* @tsk: Task for which cputime needs to be started
* @samples: Storage for time samples
*
* Called from sys_getitimer() to calculate the expiry time of an active
* timer. That means group cputime accounting is already active. Called
* with task sighand lock held.
*
* Updates @times with an uptodate sample of the thread group cputimes.
*/
void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
WARN_ON_ONCE(!pct->timers_active);
proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
}
/**
* thread_group_start_cputime - Start cputime and return a sample
* @tsk: Task for which cputime needs to be started
* @samples: Storage for time samples
*
* The thread group cputime accounting is avoided when there are no posix
* CPU timers armed. Before starting a timer it's required to check whether
* the time accounting is active. If not, a full update of the atomic
* accounting store needs to be done and the accounting enabled.
*
* Updates @times with an uptodate sample of the thread group cputimes.
*/
static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
/* Check if cputimer isn't running. This is accessed without locking. */
if (!READ_ONCE(pct->timers_active)) {
struct task_cputime sum;
/*
* 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 timers_active without a lock. Ensure this
* only gets written to in one operation. We set it after
* update_gt_cputime() as a small optimization, but
* barriers are not required because update_gt_cputime()
* can handle concurrent updates.
*/
WRITE_ONCE(pct->timers_active, true);
}
proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
}
static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
{
struct task_cputime ct;
thread_group_cputime(tsk, &ct);
store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
}
/*
* Sample a process (thread group) clock for the given task clkid. If the
* group's cputime accounting is already enabled, read the atomic
* store. Otherwise a full update is required. clkid is already validated.
*/
static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
bool start)
{
struct thread_group_cputimer *cputimer = &p->signal->cputimer;
struct posix_cputimers *pct = &p->signal->posix_cputimers;
u64 samples[CPUCLOCK_MAX];
if (!READ_ONCE(pct->timers_active)) {
if (start)
thread_group_start_cputime(p, samples);
else
__thread_group_cputime(p, samples);
} else {
proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
}
return samples[clkid];
}
static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
{
const clockid_t clkid = CPUCLOCK_WHICH(clock);
struct task_struct *tsk;
u64 t;
rcu_read_lock();
tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
if (!tsk) {
rcu_read_unlock();
return -EINVAL;
}
if (CPUCLOCK_PERTHREAD(clock))
t = cpu_clock_sample(clkid, tsk);
else
t = cpu_clock_sample_group(clkid, tsk, false);
rcu_read_unlock();
*tp = ns_to_timespec64(t);
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.
*/
static int posix_cpu_timer_create(struct k_itimer *new_timer)
{
static struct lock_class_key posix_cpu_timers_key;
struct pid *pid;
rcu_read_lock();
pid = pid_for_clock(new_timer->it_clock, false);
if (!pid) {
rcu_read_unlock();
return -EINVAL;
}
/*
* If posix timer expiry is handled in task work context then
* timer::it_lock can be taken without disabling interrupts as all
* other locking happens in task context. This requires a separate
* lock class key otherwise regular posix timer expiry would record
* the lock class being taken in interrupt context and generate a
* false positive warning.
*/
if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
new_timer->kclock = &clock_posix_cpu;
timerqueue_init(&new_timer->it.cpu.node);
new_timer->it.cpu.pid = get_pid(pid);
rcu_read_unlock();
return 0;
}
/*
* 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)
{
struct cpu_timer *ctmr = &timer->it.cpu;
struct sighand_struct *sighand;
struct task_struct *p;
unsigned long flags;
int ret = 0;
rcu_read_lock();
p = cpu_timer_task_rcu(timer);
if (!p)
goto out;
/*
* 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)) {
/*
* This raced with the reaping of the task. The exit cleanup
* should have removed this timer from the timer queue.
*/
WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
} else {
if (timer->it.cpu.firing)
ret = TIMER_RETRY;
else
cpu_timer_dequeue(ctmr);
unlock_task_sighand(p, &flags);
}
out:
rcu_read_unlock();
if (!ret)
put_pid(ctmr->pid);
return ret;
}
static void cleanup_timerqueue(struct timerqueue_head *head)
{
struct timerqueue_node *node;
struct cpu_timer *ctmr;
while ((node = timerqueue_getnext(head))) {
timerqueue_del(head, node);
ctmr = container_of(node, struct cpu_timer, node);
ctmr->head = NULL;
}
}
/*
* Clean out CPU timers which are still armed when a thread exits. The
* timers are only removed from the list. No other updates are done. The
* corresponding posix timers are still accessible, but cannot be rearmed.
*
* This must be called with the siglock held.
*/
static void cleanup_timers(struct posix_cputimers *pct)
{
cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
}
/*
* 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->posix_cputimers);
}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
cleanup_timers(&tsk->signal->posix_cputimers);
}
/*
* 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)
{
int clkidx = CPUCLOCK_WHICH(timer->it_clock);
struct cpu_timer *ctmr = &timer->it.cpu;
u64 newexp = cpu_timer_getexpires(ctmr);
struct posix_cputimer_base *base;
if (CPUCLOCK_PERTHREAD(timer->it_clock))
base = p->posix_cputimers.bases + clkidx;
else
base = p->signal->posix_cputimers.bases + clkidx;
if (!cpu_timer_enqueue(&base->tqhead, ctmr))
return;
/*
* 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.
*/
if (newexp < base->nextevt)
base->nextevt = newexp;
if (CPUCLOCK_PERTHREAD(timer->it_clock))
tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
else
tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);
}
/*
* The timer is locked, fire it and arrange for its reload.
*/
static void cpu_timer_fire(struct k_itimer *timer)
{
struct cpu_timer *ctmr = &timer->it.cpu;
if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
/*
* User don't want any signal.
*/
cpu_timer_setexpires(ctmr, 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);
cpu_timer_setexpires(ctmr, 0);
} else if (!timer->it_interval) {
/*
* One-shot timer. Clear it as soon as it's fired.
*/
posix_timer_event(timer, 0);
cpu_timer_setexpires(ctmr, 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_rearm(timer);
++timer->it_requeue_pending;
}
}
/*
* 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 itimerspec64 *new, struct itimerspec64 *old)
{
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
u64 old_expires, new_expires, old_incr, val;
struct cpu_timer *ctmr = &timer->it.cpu;
struct sighand_struct *sighand;
struct task_struct *p;
unsigned long flags;
int ret = 0;
rcu_read_lock();
p = cpu_timer_task_rcu(timer);
if (!p) {
/*
* If p has just been reaped, we can no
* longer get any information about it at all.
*/
rcu_read_unlock();
return -ESRCH;
}
/*
* Use the to_ktime conversion because that clamps the maximum
* value to KTIME_MAX and avoid multiplication overflows.
*/
new_expires = ktime_to_ns(timespec64_to_ktime(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)) {
rcu_read_unlock();
return -ESRCH;
}
/*
* Disarm any old timer after extracting its expiry time.
*/
old_incr = timer->it_interval;
old_expires = cpu_timer_getexpires(ctmr);
if (unlikely(timer->it.cpu.firing)) {
timer->it.cpu.firing = -1;
ret = TIMER_RETRY;
} else {
cpu_timer_dequeue(ctmr);
}
/*
* 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))
val = cpu_clock_sample(clkid, p);
else
val = cpu_clock_sample_group(clkid, p, true);
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.
*/
u64 exp = bump_cpu_timer(timer, val);
if (val < exp) {
old_expires = exp - val;
old->it_value = ns_to_timespec64(old_expires);
} 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).
*/
cpu_timer_setexpires(ctmr, new_expires);
if (new_expires != 0 && val < new_expires) {
arm_timer(timer, p);
}
unlock_task_sighand(p, &flags);
/*
* Install the new reload setting, and
* set up the signal and overrun bookkeeping.
*/
timer->it_interval = timespec64_to_ktime(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:
rcu_read_unlock();
if (old)
old->it_interval = ns_to_timespec64(old_incr);
return ret;
}
static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
{
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
struct cpu_timer *ctmr = &timer->it.cpu;
u64 now, expires = cpu_timer_getexpires(ctmr);
struct task_struct *p;
rcu_read_lock();
p = cpu_timer_task_rcu(timer);
if (!p)
goto out;
/*
* Easy part: convert the reload time.
*/
itp->it_interval = ktime_to_timespec64(timer->it_interval);
if (!expires)
goto out;
/*
* Sample the clock to take the difference with the expiry time.
*/
if (CPUCLOCK_PERTHREAD(timer->it_clock))
now = cpu_clock_sample(clkid, p);
else
now = cpu_clock_sample_group(clkid, p, false);
if (now < expires) {
itp->it_value = ns_to_timespec64(expires - now);
} 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;
}
out:
rcu_read_unlock();
}
#define MAX_COLLECTED 20
static u64 collect_timerqueue(struct timerqueue_head *head,
struct list_head *firing, u64 now)
{
struct timerqueue_node *next;
int i = 0;
while ((next = timerqueue_getnext(head))) {
struct cpu_timer *ctmr;
u64 expires;
ctmr = container_of(next, struct cpu_timer, node);
expires = cpu_timer_getexpires(ctmr);
/* Limit the number of timers to expire at once */
if (++i == MAX_COLLECTED || now < expires)
return expires;
ctmr->firing = 1;
cpu_timer_dequeue(ctmr);
list_add_tail(&ctmr->elist, firing);
}
return U64_MAX;
}
static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
struct list_head *firing)
{
struct posix_cputimer_base *base = pct->bases;
int i;
for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
base->nextevt = collect_timerqueue(&base->tqhead, firing,
samples[i]);
}
}
static inline void check_dl_overrun(struct task_struct *tsk)
{
if (tsk->dl.dl_overrun) {
tsk->dl.dl_overrun = 0;
__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
}
}
static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
{
if (time < limit)
return false;
if (print_fatal_signals) {
pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
rt ? "RT" : "CPU", hard ? "hard" : "soft",
current->comm, task_pid_nr(current));
}
__group_send_sig_info(signo, SEND_SIG_PRIV, current);
return true;
}
/*
* 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 posix_cputimers *pct = &tsk->posix_cputimers;
u64 samples[CPUCLOCK_MAX];
unsigned long soft;
if (dl_task(tsk))
check_dl_overrun(tsk);
if (expiry_cache_is_inactive(pct))
return;
task_sample_cputime(tsk, samples);
collect_posix_cputimers(pct, samples, firing);
/*
* Check for the special case thread timers.
*/
soft = task_rlimit(tsk, RLIMIT_RTTIME);
if (soft != RLIM_INFINITY) {
/* Task RT timeout is accounted in jiffies. RTTIME is usec */
unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
/* At the hard limit, send SIGKILL. No further action. */
if (hard != RLIM_INFINITY &&
check_rlimit(rttime, hard, SIGKILL, true, true))
return;
/* At the soft limit, send a SIGXCPU every second */
if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
soft += USEC_PER_SEC;
tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
}
}
if (expiry_cache_is_inactive(pct))
tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
}
static inline void stop_process_timers(struct signal_struct *sig)
{
struct posix_cputimers *pct = &sig->posix_cputimers;
/* Turn off the active flag. This is done without locking. */
WRITE_ONCE(pct->timers_active, false);
tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
}
static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
u64 *expires, u64 cur_time, int signo)
{
if (!it->expires)
return;
if (cur_time >= it->expires) {
if (it->incr)
it->expires += it->incr;
else
it->expires = 0;
trace_itimer_expire(signo == SIGPROF ?
ITIMER_PROF : ITIMER_VIRTUAL,
task_tgid(tsk), cur_time);
__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
}
if (it->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;
struct posix_cputimers *pct = &sig->posix_cputimers;
u64 samples[CPUCLOCK_MAX];
unsigned long soft;
/*
* If there are no active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) nothing to check. Also skip the process wide timer
* processing when there is already another task handling them.
*/
if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
return;
/*
* Signify that a thread is checking for process timers.
* Write access to this field is protected by the sighand lock.
*/
pct->expiry_active = true;
/*
* Collect the current process totals. Group accounting is active
* so the sample can be taken directly.
*/
proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
collect_posix_cputimers(pct, samples, firing);
/*
* Check for the special case process timers.
*/
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
&pct->bases[CPUCLOCK_PROF].nextevt,
samples[CPUCLOCK_PROF], SIGPROF);
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
&pct->bases[CPUCLOCK_VIRT].nextevt,
samples[CPUCLOCK_VIRT], SIGVTALRM);
soft = task_rlimit(tsk, RLIMIT_CPU);
if (soft != RLIM_INFINITY) {
/* RLIMIT_CPU is in seconds. Samples are nanoseconds */
unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
u64 ptime = samples[CPUCLOCK_PROF];
u64 softns = (u64)soft * NSEC_PER_SEC;
u64 hardns = (u64)hard * NSEC_PER_SEC;
/* At the hard limit, send SIGKILL. No further action. */
if (hard != RLIM_INFINITY &&
check_rlimit(ptime, hardns, SIGKILL, false, true))
return;
/* At the soft limit, send a SIGXCPU every second */
if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
softns += NSEC_PER_SEC;
}
/* Update the expiry cache */
if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
pct->bases[CPUCLOCK_PROF].nextevt = softns;
}
if (expiry_cache_is_inactive(pct))
stop_process_timers(sig);
pct->expiry_active = false;
}
/*
* This is called from the signal code (via posixtimer_rearm)
* when the last timer signal was delivered and we have to reload the timer.
*/
static void posix_cpu_timer_rearm(struct k_itimer *timer)
{
clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
struct task_struct *p;
struct sighand_struct *sighand;
unsigned long flags;
u64 now;
rcu_read_lock();
p = cpu_timer_task_rcu(timer);
if (!p)
goto out;
/*
* Fetch the current sample and update the timer's expiry time.
*/
if (CPUCLOCK_PERTHREAD(timer->it_clock))
now = cpu_clock_sample(clkid, p);
else
now = cpu_clock_sample_group(clkid, p, true);
bump_cpu_timer(timer, now);
/* Protect timer list r/w in arm_timer() */
sighand = lock_task_sighand(p, &flags);
if (unlikely(sighand == NULL))
goto out;
/*
* Now re-arm for the new expiry time.
*/
arm_timer(timer, p);
unlock_task_sighand(p, &flags);
out:
rcu_read_unlock();
}
/**
* task_cputimers_expired - Check whether posix CPU timers are expired
*
* @samples: Array of current samples for the CPUCLOCK clocks
* @pct: Pointer to a posix_cputimers container
*
* Returns true if any member of @samples is greater than the corresponding
* member of @pct->bases[CLK].nextevt. False otherwise
*/
static inline bool
task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
{
int i;
for (i = 0; i < CPUCLOCK_MAX; i++) {
if (samples[i] >= pct->bases[i].nextevt)
return true;
}
return false;
}
/**
* 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 bool fastpath_timer_check(struct task_struct *tsk)
{
struct posix_cputimers *pct = &tsk->posix_cputimers;
struct signal_struct *sig;
if (!expiry_cache_is_inactive(pct)) {
u64 samples[CPUCLOCK_MAX];
task_sample_cputime(tsk, samples);
if (task_cputimers_expired(samples, pct))
return true;
}
sig = tsk->signal;
pct = &sig->posix_cputimers;
/*
* Check if thread group timers expired when timers are active and
* no other thread in the group is already handling expiry 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 handle timer expiry.
*
* In the worst case scenario, if concurrently timers_active is set
* or expiry_active is cleared, but the current thread doesn't see
* the change yet, the timer checks are delayed 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(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
u64 samples[CPUCLOCK_MAX];
proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
samples);
if (task_cputimers_expired(samples, pct))
return true;
}
if (dl_task(tsk) && tsk->dl.dl_overrun)
return true;
return false;
}
static void handle_posix_cpu_timers(struct task_struct *tsk);
#ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
static void posix_cpu_timers_work(struct callback_head *work)
{
handle_posix_cpu_timers(current);
}
/*
* Initialize posix CPU timers task work in init task. Out of line to
* keep the callback static and to avoid header recursion hell.
*/
void __init posix_cputimers_init_work(void)
{
init_task_work(&current->posix_cputimers_work.work,
posix_cpu_timers_work);
}
/*
* Note: All operations on tsk->posix_cputimer_work.scheduled happen either
* in hard interrupt context or in task context with interrupts
* disabled. Aside of that the writer/reader interaction is always in the
* context of the current task, which means they are strict per CPU.
*/
static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
{
return tsk->posix_cputimers_work.scheduled;
}
static inline void __run_posix_cpu_timers(struct task_struct *tsk)
{
if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
return;
/* Schedule task work to actually expire the timers */
tsk->posix_cputimers_work.scheduled = true;
task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
}
static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
unsigned long start)
{
bool ret = true;
/*
* On !RT kernels interrupts are disabled while collecting expired
* timers, so no tick can happen and the fast path check can be
* reenabled without further checks.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
tsk->posix_cputimers_work.scheduled = false;
return true;
}
/*
* On RT enabled kernels ticks can happen while the expired timers
* are collected under sighand lock. But any tick which observes
* the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
* checks. So reenabling the tick work has do be done carefully:
*
* Disable interrupts and run the fast path check if jiffies have
* advanced since the collecting of expired timers started. If
* jiffies have not advanced or the fast path check did not find
* newly expired timers, reenable the fast path check in the timer
* interrupt. If there are newly expired timers, return false and
* let the collection loop repeat.
*/
local_irq_disable();
if (start != jiffies && fastpath_timer_check(tsk))
ret = false;
else
tsk->posix_cputimers_work.scheduled = false;
local_irq_enable();
return ret;
}
#else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
static inline void __run_posix_cpu_timers(struct task_struct *tsk)
{
lockdep_posixtimer_enter();
handle_posix_cpu_timers(tsk);
lockdep_posixtimer_exit();
}
static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
{
return false;
}
static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
unsigned long start)
{
return true;
}
#endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
static void handle_posix_cpu_timers(struct task_struct *tsk)
{
struct k_itimer *timer, *next;
unsigned long flags, start;
LIST_HEAD(firing);
if (!lock_task_sighand(tsk, &flags))
return;
do {
/*
* On RT locking sighand lock does not disable interrupts,
* so this needs to be careful vs. ticks. Store the current
* jiffies value.
*/
start = READ_ONCE(jiffies);
barrier();
/*
* 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);
/*
* The above timer checks have updated the expiry cache and
* because nothing can have queued or modified timers after
* sighand lock was taken above it is guaranteed to be
* consistent. So the next timer interrupt fastpath check
* will find valid data.
*
* If timer expiry runs in the timer interrupt context then
* the loop is not relevant as timers will be directly
* expired in interrupt context. The stub function below
* returns always true which allows the compiler to
* optimize the loop out.
*
* If timer expiry is deferred to task work context then
* the following rules apply:
*
* - On !RT kernels no tick can have happened on this CPU
* after sighand lock was acquired because interrupts are
* disabled. So reenabling task work before dropping
* sighand lock and reenabling interrupts is race free.
*
* - On RT kernels ticks might have happened but the tick
* work ignored posix CPU timer handling because the
* CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
* must be done very carefully including a check whether
* ticks have happened since the start of the timer
* expiry checks. posix_cpu_timers_enable_work() takes
* care of that and eventually lets the expiry checks
* run again.
*/
} while (!posix_cpu_timers_enable_work(tsk, start));
/*
* We must release sighand lock 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.elist) {
int cpu_firing;
/*
* spin_lock() is sufficient here even independent of the
* expiry context. If expiry happens in hard interrupt
* context it's obvious. For task work context it's safe
* because all other operations on timer::it_lock happen in
* task context (syscall or exit).
*/
spin_lock(&timer->it_lock);
list_del_init(&timer->it.cpu.elist);
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);
}
}
/*
* 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(void)
{
struct task_struct *tsk = current;
lockdep_assert_irqs_disabled();
/*
* If the actual expiry is deferred to task work context and the
* work is already scheduled there is no point to do anything here.
*/
if (posix_cpu_timers_work_scheduled(tsk))
return;
/*
* 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;
__run_posix_cpu_timers(tsk);
}
/*
* 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 clkid,
u64 *newval, u64 *oldval)
{
u64 now, *nextevt;
if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
return;
nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
now = cpu_clock_sample_group(clkid, tsk, true);
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 = TICK_NSEC;
} else {
*oldval -= now;
}
}
if (!*newval)
return;
*newval += now;
}
/*
* Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
* expiry cache is also used by RLIMIT_CPU!.
*/
if (*newval < *nextevt)
*nextevt = *newval;
tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
}
static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
const struct timespec64 *rqtp)
{
struct itimerspec64 it;
struct k_itimer timer;
u64 expires;
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 itimerspec64 zero_it;
struct restart_block *restart;
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 (!cpu_timer_getexpires(&timer.it.cpu)) {
/*
* 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.
*/
expires = cpu_timer_getexpires(&timer.it.cpu);
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;
/*
* Report back to the user the time still remaining.
*/
restart = &current->restart_block;
restart->nanosleep.expires = expires;
if (restart->nanosleep.type != TT_NONE)
error = nanosleep_copyout(restart, &it.it_value);
}
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,
const struct timespec64 *rqtp)
{
struct restart_block *restart_block = &current->restart_block;
int error;
/*
* Diagnose required errors first.
*/
if (CPUCLOCK_PERTHREAD(which_clock) &&
(CPUCLOCK_PID(which_clock) == 0 ||
CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
return -EINVAL;
error = do_cpu_nanosleep(which_clock, flags, rqtp);
if (error == -ERESTART_RESTARTBLOCK) {
if (flags & TIMER_ABSTIME)
return -ERESTARTNOHAND;
restart_block->nanosleep.clockid = which_clock;
set_restart_fn(restart_block, posix_cpu_nsleep_restart);
}
return error;
}
static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
{
clockid_t which_clock = restart_block->nanosleep.clockid;
struct timespec64 t;
t = ns_to_timespec64(restart_block->nanosleep.expires);
return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
}
#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 timespec64 *tp)
{
return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
}
static int process_cpu_clock_get(const clockid_t which_clock,
struct timespec64 *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,
const struct timespec64 *rqtp)
{
return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
}
static int thread_cpu_clock_getres(const clockid_t which_clock,
struct timespec64 *tp)
{
return posix_cpu_clock_getres(THREAD_CLOCK, tp);
}
static int thread_cpu_clock_get(const clockid_t which_clock,
struct timespec64 *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);
}
const struct k_clock clock_posix_cpu = {
.clock_getres = posix_cpu_clock_getres,
.clock_set = posix_cpu_clock_set,
.clock_get_timespec = posix_cpu_clock_get,
.timer_create = posix_cpu_timer_create,
.nsleep = posix_cpu_nsleep,
.timer_set = posix_cpu_timer_set,
.timer_del = posix_cpu_timer_del,
.timer_get = posix_cpu_timer_get,
.timer_rearm = posix_cpu_timer_rearm,
};
const struct k_clock clock_process = {
.clock_getres = process_cpu_clock_getres,
.clock_get_timespec = process_cpu_clock_get,
.timer_create = process_cpu_timer_create,
.nsleep = process_cpu_nsleep,
};
const struct k_clock clock_thread = {
.clock_getres = thread_cpu_clock_getres,
.clock_get_timespec = thread_cpu_clock_get,
.timer_create = thread_cpu_timer_create,
};