diff options
Diffstat (limited to '')
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 1452 |
1 files changed, 1452 insertions, 0 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c new file mode 100644 index 000000000..bfaa44a80 --- /dev/null +++ b/kernel/time/posix-cpu-timers.c @@ -0,0 +1,1452 @@ +// 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); + +/* + * 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) +{ + 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); +} + +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; +} + +/* + * Update expiry time from increment, and increase overrun count, + * given the current clock sample. + */ +static void bump_cpu_timer(struct k_itimer *timer, u64 now) +{ + int i; + u64 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 += 1LL << 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 u64 prof_ticks(struct task_struct *p) +{ + u64 utime, stime; + + task_cputime(p, &utime, &stime); + + return utime + stime; +} +static inline u64 virt_ticks(struct task_struct *p) +{ + u64 utime, stime; + + task_cputime(p, &utime, &stime); + + return utime; +} + +static int +posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *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 timespec64 *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, u64 *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, + u64 *sample) +{ + struct task_cputime cputime; + + switch (CPUCLOCK_WHICH(which_clock)) { + default: + return -EINVAL; + case CPUCLOCK_PROF: + thread_group_cputime(p, &cputime); + *sample = cputime.utime + cputime.stime; + break; + case CPUCLOCK_VIRT: + thread_group_cputime(p, &cputime); + *sample = 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 timespec64 *tp) +{ + int err = -EINVAL; + u64 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) + *tp = ns_to_timespec64(rtn); + + return err; +} + + +static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec64 *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; + + new_timer->kclock = &clock_posix_cpu; + + 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; + + if (WARN_ON_ONCE(!p)) + return -EINVAL; + + /* + * 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) +{ + 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(u64 expires, u64 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) { + u64 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)) + cputime_expires->prof_exp = exp; + break; + case CPUCLOCK_VIRT: + if (expires_gt(cputime_expires->virt_exp, exp)) + cputime_expires->virt_exp = exp; + break; + case CPUCLOCK_SCHED: + if (expires_gt(cputime_expires->sched_exp, exp)) + cputime_expires->sched_exp = exp; + break; + } + 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) +{ + 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_rearm(timer); + ++timer->it_requeue_pending; + } +} + +/* + * 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, u64 *sample) +{ + struct task_cputime cputime; + + thread_group_cputimer(p, &cputime); + switch (CPUCLOCK_WHICH(which_clock)) { + default: + return -EINVAL; + case CPUCLOCK_PROF: + *sample = cputime.utime + cputime.stime; + break; + case CPUCLOCK_VIRT: + *sample = cputime.utime; + break; + case CPUCLOCK_SCHED: + *sample = cputime.sum_exec_runtime; + 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.) + */ +static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, + struct itimerspec64 *new, struct itimerspec64 *old) +{ + unsigned long flags; + struct sighand_struct *sighand; + struct task_struct *p = timer->it.cpu.task; + u64 old_expires, new_expires, old_incr, val; + int ret; + + if (WARN_ON_ONCE(!p)) + return -EINVAL; + + /* + * 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)) { + return -ESRCH; + } + + /* + * Disarm any old timer after extracting its expiry time. + */ + + 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; + 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). + */ + 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 = timespec64_to_ns(&new->it_interval); + timer->it_interval = ns_to_ktime(timer->it.cpu.incr); + + /* + * 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) + old->it_interval = ns_to_timespec64(old_incr); + + return ret; +} + +static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp) +{ + struct task_struct *p = timer->it.cpu.task; + u64 now; + + if (WARN_ON_ONCE(!p)) + return; + + /* + * Easy part: convert the reload time. + */ + itp->it_interval = ns_to_timespec64(timer->it.cpu.incr); + + if (!timer->it.cpu.expires) + 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; + return; + } else { + cpu_timer_sample_group(timer->it_clock, p, &now); + unlock_task_sighand(p, &flags); + } + } + + if (now < timer->it.cpu.expires) { + itp->it_value = ns_to_timespec64(timer->it.cpu.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; + } +} + +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; +} + +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); + } +} + +/* + * 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 task_cputime *tsk_expires = &tsk->cputime_expires; + u64 expires; + unsigned long soft; + + if (dl_task(tsk)) + check_dl_overrun(tsk); + + /* + * 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; + + expires = check_timers_list(++timers, firing, virt_ticks(tsk)); + tsk_expires->virt_exp = expires; + + tsk_expires->sched_exp = check_timers_list(++timers, firing, + tsk->se.sum_exec_runtime); + + /* + * Check for the special case thread timers. + */ + soft = task_rlimit(tsk, RLIMIT_RTTIME); + if (soft != RLIM_INFINITY) { + unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME); + + 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. + */ + if (print_fatal_signals) { + pr_info("CPU Watchdog Timeout (hard): %s[%d]\n", + tsk->comm, task_pid_nr(tsk)); + } + __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; + tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = + soft; + } + if (print_fatal_signals) { + pr_info("RT Watchdog Timeout (soft): %s[%d]\n", + tsk->comm, task_pid_nr(tsk)); + } + __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk); + } + } + if (task_cputime_zero(tsk_expires)) + tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER); +} + +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); + 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 && (!*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; + u64 utime, ptime, virt_expires, prof_expires; + u64 sum_sched_runtime, sched_expires; + struct list_head *timers = sig->cpu_timers; + struct task_cputime cputime; + unsigned long soft; + + if (dl_task(tsk)) + check_dl_overrun(tsk); + + /* + * 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.utime; + ptime = utime + 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 = task_rlimit(tsk, RLIMIT_CPU); + if (soft != RLIM_INFINITY) { + unsigned long psecs = div_u64(ptime, NSEC_PER_SEC); + unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU); + u64 x; + if (psecs >= hard) { + /* + * At the hard limit, we just die. + * No need to calculate anything else now. + */ + if (print_fatal_signals) { + pr_info("RT Watchdog Timeout (hard): %s[%d]\n", + tsk->comm, task_pid_nr(tsk)); + } + __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk); + return; + } + if (psecs >= soft) { + /* + * At the soft limit, send a SIGXCPU every second. + */ + if (print_fatal_signals) { + pr_info("CPU Watchdog Timeout (soft): %s[%d]\n", + tsk->comm, task_pid_nr(tsk)); + } + __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk); + if (soft < hard) { + soft++; + sig->rlim[RLIMIT_CPU].rlim_cur = soft; + } + } + x = soft * NSEC_PER_SEC; + if (!prof_expires || 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); + + sig->cputimer.checking_timer = 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) +{ + struct task_struct *p = timer->it.cpu.task; + struct sighand_struct *sighand; + unsigned long flags; + u64 now; + + if (WARN_ON_ONCE(!p)) + return; + + /* + * 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)) + return; + + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (!sighand) + return; + } 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; + return; + } else if (unlikely(p->exit_state) && thread_group_empty(p)) { + /* If the process is dying, no need to rearm */ + goto unlock; + } + 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. + */ + arm_timer(timer); +unlock: + unlock_task_sighand(p, &flags); +} + +/** + * 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; + } + + if (dl_task(tsk) && tsk->dl.dl_overrun) + 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; + + lockdep_assert_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, + u64 *newval, u64 *oldval) +{ + u64 now; + int ret; + + if (WARN_ON_ONCE(clock_idx >= CPUCLOCK_SCHED)) + return; + + ret = cpu_timer_sample_group(clock_idx, tsk, &now); + + if (oldval && ret != -EINVAL) { + /* + * 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 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; + } + + 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 (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. + */ + expires = timer.it.cpu.expires; + 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 = ¤t->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 = ¤t->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 = 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 = 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 = thread_cpu_clock_get, + .timer_create = thread_cpu_timer_create, +}; |