diff options
Diffstat (limited to 'kernel/time/posix-cpu-timers.c')
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 1694 |
1 files changed, 961 insertions, 733 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 8f0644af40be..0de2bb7cbec0 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -15,66 +15,123 @@ #include <linux/workqueue.h> #include <linux/compat.h> #include <linux/sched/deadline.h> +#include <linux/task_work.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->cputime_expires expiration cache if necessary. Needs - * siglock protection since other code may update expiration cache as - * well. + * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if + * necessary. Needs siglock protection since other code may update the + * expiration cache as well. + * + * Returns 0 on success, -ESRCH on failure. Can fail if the task is exiting and + * we cannot lock_task_sighand. Cannot fail if task is current. */ -void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) +int update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new) { u64 nsecs = rlim_new * NSEC_PER_SEC; + unsigned long irq_fl; - spin_lock_irq(&task->sighand->siglock); + if (!lock_task_sighand(task, &irq_fl)) + return -ESRCH; set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL); - spin_unlock_irq(&task->sighand->siglock); + unlock_task_sighand(task, &irq_fl); + return 0; } -static int check_clock(const clockid_t which_clock) +/* + * Functions for validating access to tasks. + */ +static struct pid *pid_for_clock(const clockid_t clock, bool gettime) { - int error = 0; - struct task_struct *p; - const pid_t pid = CPUCLOCK_PID(which_clock); + const bool thread = !!CPUCLOCK_PERTHREAD(clock); + const pid_t upid = CPUCLOCK_PID(clock); + struct pid *pid; - if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX) - return -EINVAL; + if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX) + return NULL; - if (pid == 0) - return 0; + /* + * 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); - 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; + 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 error; + 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 void bump_cpu_timer(struct k_itimer *timer, u64 now) +static u64 bump_cpu_timer(struct k_itimer *timer, u64 now) { + u64 delta, incr, expires = timer->it.cpu.node.expires; int i; - u64 delta, incr; - if (timer->it.cpu.incr == 0) - return; + if (!timer->it_interval) + return expires; - if (now < timer->it.cpu.expires) - return; + if (now < expires) + return expires; - incr = timer->it.cpu.incr; - delta = now + incr - timer->it.cpu.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++) @@ -84,48 +141,26 @@ static void bump_cpu_timer(struct k_itimer *timer, u64 now) if (delta < incr) continue; - timer->it.cpu.expires += incr; + timer->it.cpu.node.expires += incr; timer->it_overrun += 1LL << i; delta -= incr; } + return timer->it.cpu.node.expires; } -/** - * task_cputime_zero - Check a task_cputime struct for all zero fields. - * - * @cputime: The struct to compare. - * - * Checks @cputime to see if all fields are zero. Returns true if all fields - * are zero, false if any field is nonzero. - */ -static inline int task_cputime_zero(const struct task_cputime *cputime) -{ - if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime) - return 1; - return 0; -} - -static inline u64 prof_ticks(struct task_struct *p) +/* 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) { - 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; + 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 = check_clock(which_clock); + int error = validate_clock_permissions(which_clock); + if (!error) { tp->tv_sec = 0; tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ); @@ -142,80 +177,132 @@ posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp) } static int -posix_cpu_clock_set(const clockid_t which_clock, const struct timespec64 *tp) +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. */ - int error = check_clock(which_clock); - if (error == 0) { - error = -EPERM; - } - return error; + return error ? : -EPERM; } - /* - * Sample a per-thread clock for the given task. + * Sample a per-thread clock for the given task. clkid is validated. */ -static int cpu_clock_sample(const clockid_t which_clock, - struct task_struct *p, u64 *sample) +static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p) { - switch (CPUCLOCK_WHICH(which_clock)) { - default: - return -EINVAL; + u64 utime, stime; + + if (clkid == CPUCLOCK_SCHED) + return task_sched_runtime(p); + + task_cputime(p, &utime, &stime); + + switch (clkid) { case CPUCLOCK_PROF: - *sample = prof_ticks(p); - break; + return utime + stime; case CPUCLOCK_VIRT: - *sample = virt_ticks(p); - break; - case CPUCLOCK_SCHED: - *sample = task_sched_runtime(p); - break; + 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; - } + u64 curr_cputime = atomic64_read(cputime); + + do { + if (sum_cputime <= curr_cputime) + return; + } while (!atomic64_try_cmpxchg(cputime, &curr_cputime, sum_cputime)); } -static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum) +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) +/** + * 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) { - 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); + 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); } -void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times) +/** + * 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 task_cputime sum; + struct posix_cputimers *pct = &tsk->signal->posix_cputimers; + + lockdep_assert_task_sighand_held(tsk); /* Check if cputimer isn't running. This is accessed without locking. */ - if (!READ_ONCE(cputimer->running)) { + 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 @@ -225,94 +312,70 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times) 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() + * 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(cputimer->running, true); + WRITE_ONCE(pct->timers_active, true); } - sample_cputime_atomic(times, &cputimer->cputime_atomic); + proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples); } -/* - * 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) +static void __thread_group_cputime(struct task_struct *tsk, u64 *samples) { - struct task_cputime cputime; + struct task_cputime ct; - 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; + thread_group_cputime(tsk, &ct); + store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime); } -static int posix_cpu_clock_get_task(struct task_struct *tsk, - const clockid_t which_clock, - struct timespec64 *tp) +/* + * 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) { - int err = -EINVAL; - u64 rtn; + struct thread_group_cputimer *cputimer = &p->signal->cputimer; + struct posix_cputimers *pct = &p->signal->posix_cputimers; + u64 samples[CPUCLOCK_MAX]; - if (CPUCLOCK_PERTHREAD(which_clock)) { - if (same_thread_group(tsk, current)) - err = cpu_clock_sample(which_clock, tsk, &rtn); + if (!READ_ONCE(pct->timers_active)) { + if (start) + thread_group_start_cputime(p, samples); + else + __thread_group_cputime(p, samples); } else { - if (tsk == current || thread_group_leader(tsk)) - err = cpu_clock_sample_group(which_clock, tsk, &rtn); + proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples); } - if (!err) - *tp = ns_to_timespec64(rtn); - - return err; + return samples[clkid]; } - -static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec64 *tp) +static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp) { - const pid_t pid = CPUCLOCK_PID(which_clock); - int err = -EINVAL; + const clockid_t clkid = CPUCLOCK_WHICH(clock); + struct task_struct *tsk; + u64 t; - 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_lock(); + tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock)); + if (!tsk) { rcu_read_unlock(); + return -EINVAL; } - return err; + 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; } /* @@ -322,46 +385,83 @@ static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec64 *t */ 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; + static struct lock_class_key posix_cpu_timers_key; + struct pid *pid; - if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX) + 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; +} - INIT_LIST_HEAD(&new_timer->it.cpu.entry); +static struct posix_cputimer_base *timer_base(struct k_itimer *timer, + struct task_struct *tsk) +{ + int clkidx = CPUCLOCK_WHICH(timer->it_clock); - 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(); + if (CPUCLOCK_PERTHREAD(timer->it_clock)) + return tsk->posix_cputimers.bases + clkidx; + else + return tsk->signal->posix_cputimers.bases + clkidx; +} - return ret; +/* + * Force recalculating the base earliest expiration on the next tick. + * This will also re-evaluate the need to keep around the process wide + * cputime counter and tick dependency and eventually shut these down + * if necessary. + */ +static void trigger_base_recalc_expires(struct k_itimer *timer, + struct task_struct *tsk) +{ + struct posix_cputimer_base *base = timer_base(timer, tsk); + + base->nextevt = 0; +} + +/* + * Dequeue the timer and reset the base if it was its earliest expiration. + * It makes sure the next tick recalculates the base next expiration so we + * don't keep the costly process wide cputime counter around for a random + * amount of time, along with the tick dependency. + * + * If another timer gets queued between this and the next tick, its + * expiration will update the base next event if necessary on the next + * tick. + */ +static void disarm_timer(struct k_itimer *timer, struct task_struct *p) +{ + struct cpu_timer *ctmr = &timer->it.cpu; + struct posix_cputimer_base *base; + + if (!cpu_timer_dequeue(ctmr)) + return; + + base = timer_base(timer, p); + if (cpu_timer_getexpires(ctmr) == base->nextevt) + trigger_base_recalc_expires(timer, p); } + /* * Clean up a CPU-clock timer that is about to be destroyed. * This is called from timer deletion with the timer already locked. @@ -370,12 +470,16 @@ static int posix_cpu_timer_create(struct k_itimer *new_timer) */ static int posix_cpu_timer_del(struct k_itimer *timer) { - int ret = 0; - unsigned long flags; + struct cpu_timer *ctmr = &timer->it.cpu; struct sighand_struct *sighand; - struct task_struct *p = timer->it.cpu.task; + struct task_struct *p; + unsigned long flags; + int ret = 0; - WARN_ON_ONCE(p == NULL); + rcu_read_lock(); + p = cpu_timer_task_rcu(timer); + if (!p) + goto out; /* * Protect against sighand release/switch in exit/exec and process/ @@ -384,44 +488,60 @@ static int posix_cpu_timer_del(struct k_itimer *timer) 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. + * This raced with the reaping of the task. The exit cleanup + * should have removed this timer from the timer queue. */ - WARN_ON_ONCE(!list_empty(&timer->it.cpu.entry)); + WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node)); } else { - if (timer->it.cpu.firing) + if (timer->it.cpu.firing) { + /* + * Prevent signal delivery. The timer cannot be dequeued + * because it is on the firing list which is not protected + * by sighand->lock. The delivery path is waiting for + * the timer lock. So go back, unlock and retry. + */ + timer->it.cpu.firing = false; ret = TIMER_RETRY; - else - list_del(&timer->it.cpu.entry); - + } else { + disarm_timer(timer, p); + } unlock_task_sighand(p, &flags); } - if (!ret) - put_task_struct(p); +out: + rcu_read_unlock(); + if (!ret) { + put_pid(ctmr->pid); + timer->it_status = POSIX_TIMER_DISARMED; + } return ret; } -static void cleanup_timers_list(struct list_head *head) +static void cleanup_timerqueue(struct timerqueue_head *head) { - struct cpu_timer_list *timer, *next; + struct timerqueue_node *node; + struct cpu_timer *ctmr; - list_for_each_entry_safe(timer, next, head, entry) - list_del_init(&timer->entry); + while ((node = timerqueue_getnext(head))) { + timerqueue_del(head, node); + ctmr = container_of(node, struct cpu_timer, node); + ctmr->head = NULL; + } } /* - * 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. + * 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 list_head *head) +static void cleanup_timers(struct posix_cputimers *pct) { - cleanup_timers_list(head); - cleanup_timers_list(++head); - cleanup_timers_list(++head); + cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead); + cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead); + cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead); } /* @@ -431,76 +551,40 @@ static void cleanup_timers(struct list_head *head) */ void posix_cpu_timers_exit(struct task_struct *tsk) { - cleanup_timers(tsk->cpu_timers); + cleanup_timers(&tsk->posix_cputimers); } 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; + 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) +static void arm_timer(struct k_itimer *timer, struct task_struct *p) { - 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; + struct posix_cputimer_base *base = timer_base(timer, p); + struct cpu_timer *ctmr = &timer->it.cpu; + u64 newexp = cpu_timer_getexpires(ctmr); - 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; + timer->it_status = POSIX_TIMER_ARMED; + 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. - */ + /* + * 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; - 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); - } + if (CPUCLOCK_PERTHREAD(timer->it_clock)) + tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER); + else + tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER); } /* @@ -508,62 +592,26 @@ static void arm_timer(struct k_itimer *timer) */ 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)) { + struct cpu_timer *ctmr = &timer->it.cpu; + + timer->it_status = POSIX_TIMER_DISARMED; + + if (unlikely(ctmr->nanosleep)) { /* * 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; + cpu_timer_setexpires(ctmr, 0); + } else { + posix_timer_queue_signal(timer); + /* Disable oneshot timers */ + if (!timer->it_interval) + cpu_timer_setexpires(ctmr, 0); } } -/* - * 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; -} +static void __posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp, u64 now); /* * Guts of sys_timer_settime for CPU timers. @@ -574,13 +622,25 @@ static int cpu_timer_sample_group(const clockid_t which_clock, static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, struct itimerspec64 *new, struct itimerspec64 *old) { - unsigned long flags; + bool sigev_none = timer->it_sigev_notify == SIGEV_NONE; + clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock); + struct cpu_timer *ctmr = &timer->it.cpu; + u64 old_expires, new_expires, now; struct sighand_struct *sighand; - struct task_struct *p = timer->it.cpu.task; - u64 old_expires, new_expires, old_incr, val; - int ret; + struct task_struct *p; + unsigned long flags; + int ret = 0; - WARN_ON_ONCE(p == NULL); + 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 @@ -598,205 +658,203 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, * 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. - */ + /* Retrieve the current expiry time before disarming the timer */ + old_expires = cpu_timer_getexpires(ctmr); - 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; + /* + * Prevent signal delivery. The timer cannot be dequeued + * because it is on the firing list which is not protected + * by sighand->lock. The delivery path is waiting for + * the timer lock. So go back, unlock and retry. + */ + timer->it.cpu.firing = false; ret = TIMER_RETRY; - } else - list_del_init(&timer->it.cpu.entry); + } else { + cpu_timer_dequeue(ctmr); + timer->it_status = POSIX_TIMER_DISARMED; + } /* - * 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. + * Sample the current clock for saving the previous setting + * and for rearming the timer. */ - 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 (CPUCLOCK_PERTHREAD(timer->it_clock)) + now = cpu_clock_sample(clkid, p); + else + now = cpu_clock_sample_group(clkid, p, !sigev_none); + /* Retrieve the previous expiry value if requested. */ 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; - } - } + old->it_value = (struct timespec64){ }; + if (old_expires) + __posix_cpu_timer_get(timer, old, now); } + /* Retry if the timer expiry is running concurrently */ 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; - } + /* Convert relative expiry time to absolute */ + if (new_expires && !(timer_flags & TIMER_ABSTIME)) + new_expires += now; + + /* Set the new expiry time (might be 0) */ + cpu_timer_setexpires(ctmr, new_expires); /* - * 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). + * Arm the timer if it is not disabled, the new expiry value has + * not yet expired and the timer requires signal delivery. + * SIGEV_NONE timers are never armed. In case the timer is not + * armed, enforce the reevaluation of the timer base so that the + * process wide cputime counter can be disabled eventually. */ - timer->it.cpu.expires = new_expires; - if (new_expires != 0 && val < new_expires) { - arm_timer(timer); + if (likely(!sigev_none)) { + if (new_expires && now < new_expires) + arm_timer(timer, p); + else + trigger_base_recalc_expires(timer, p); } 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); + + posix_timer_set_common(timer, new); /* - * 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. + * If the new expiry time was already in the past the timer was not + * queued. Fire it immediately even if the thread never runs to + * accumulate more time on this clock. */ - 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. - */ + if (!sigev_none && new_expires && now >= new_expires) cpu_timer_fire(timer); - } - - ret = 0; - out: - if (old) - old->it_interval = ns_to_timespec64(old_incr); - +out: + rcu_read_unlock(); return ret; } -static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp) +static void __posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp, u64 now) { - u64 now; - struct task_struct *p = timer->it.cpu.task; - - WARN_ON_ONCE(p == NULL); + bool sigev_none = timer->it_sigev_notify == SIGEV_NONE; + u64 expires, iv = timer->it_interval; /* - * Easy part: convert the reload time. + * Make sure that interval timers are moved forward for the + * following cases: + * - SIGEV_NONE timers which are never armed + * - Timers which expired, but the signal has not yet been + * delivered */ - itp->it_interval = ns_to_timespec64(timer->it.cpu.incr); - - if (!timer->it.cpu.expires) - return; + if (iv && timer->it_status != POSIX_TIMER_ARMED) + expires = bump_cpu_timer(timer, now); + else + expires = cpu_timer_getexpires(&timer->it.cpu); /* - * Sample the clock to take the difference with the expiry time. + * Expired interval timers cannot have a remaining time <= 0. + * The kernel has to move them forward so that the next + * timer expiry is > @now. */ - 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); + 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. + * A single shot SIGEV_NONE timer must return 0, when it is + * expired! Timers which have a real signal delivery mode + * must return a remaining time greater than 0 because the + * signal has not yet been delivered. */ - itp->it_value.tv_nsec = 1; - itp->it_value.tv_sec = 0; + if (!sigev_none) + itp->it_value.tv_nsec = 1; } } -static unsigned long long -check_timers_list(struct list_head *timers, - struct list_head *firing, - unsigned long long curr) +static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp) { - int maxfire = 20; + clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock); + struct task_struct *p; + u64 now; - while (!list_empty(timers)) { - struct cpu_timer_list *t; + rcu_read_lock(); + p = cpu_timer_task_rcu(timer); + if (p && cpu_timer_getexpires(&timer->it.cpu)) { + itp->it_interval = ktime_to_timespec64(timer->it_interval); - t = list_first_entry(timers, struct cpu_timer_list, entry); + if (CPUCLOCK_PERTHREAD(timer->it_clock)) + now = cpu_clock_sample(clkid, p); + else + now = cpu_clock_sample_group(clkid, p, false); - if (!--maxfire || curr < t->expires) - return t->expires; + __posix_cpu_timer_get(timer, itp, now); + } + rcu_read_unlock(); +} + +#define MAX_COLLECTED 20 - t->firing = 1; - list_move_tail(&t->entry, firing); +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 = true; + /* See posix_cpu_timer_wait_running() */ + rcu_assign_pointer(ctmr->handling, current); + cpu_timer_dequeue(ctmr); + list_add_tail(&ctmr->elist, firing); } - return 0; + 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); + send_signal_locked(SIGXCPU, SEND_SIG_PRIV, tsk, PIDTYPE_TGID); + } +} + +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)); } + send_signal_locked(signo, SEND_SIG_PRIV, current, PIDTYPE_TGID); + return true; } /* @@ -807,76 +865,50 @@ static inline void check_dl_overrun(struct task_struct *tsk) 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; + struct posix_cputimers *pct = &tsk->posix_cputimers; + u64 samples[CPUCLOCK_MAX]; 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)) + if (expiry_cache_is_inactive(pct)) 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); + 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 && - 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); + check_rlimit(rttime, hard, SIGKILL, true, true)) 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); + + /* 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 (task_cputime_zero(tsk_expires)) + + 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 thread_group_cputimer *cputimer = &sig->cputimer; + struct posix_cputimers *pct = &sig->posix_cputimers; - /* Turn off cputimer->running. This is done without locking. */ - WRITE_ONCE(cputimer->running, false); + /* 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); } @@ -895,10 +927,10 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it, trace_itimer_expire(signo == SIGPROF ? ITIMER_PROF : ITIMER_VIRTUAL, task_tgid(tsk), cur_time); - __group_send_sig_info(signo, SEND_SIG_PRIV, tsk); + send_signal_locked(signo, SEND_SIG_PRIV, tsk, PIDTYPE_TGID); } - if (it->expires && (!*expires || it->expires < *expires)) + if (it->expires && it->expires < *expires) *expires = it->expires; } @@ -911,87 +943,69 @@ 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; + struct posix_cputimers *pct = &sig->posix_cputimers; + u64 samples[CPUCLOCK_MAX]; unsigned long soft; /* - * If cputimer is not running, then there are no active - * process wide timers (POSIX 1.b, itimers, RLIMIT_CPU). + * 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(tsk->signal->cputimer.running)) + 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. */ - sig->cputimer.checking_timer = true; + pct->expiry_active = true; /* - * Collect the current process totals. + * Collect the current process totals. Group accounting is active + * so the sample can be taken directly. */ - 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); + 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], &prof_expires, ptime, - SIGPROF); - check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime, - SIGVTALRM); + 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) { - unsigned long psecs = div_u64(ptime, NSEC_PER_SEC); + /* RLIMIT_CPU is in seconds. Samples are nanoseconds */ 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); + 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; } - 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; + + /* Update the expiry cache */ + if (softns < pct->bases[CPUCLOCK_PROF].nextevt) + pct->bases[CPUCLOCK_PROF].nextevt = softns; } - 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)) + if (expiry_cache_is_inactive(pct)) stop_process_timers(sig); - sig->cputimer.checking_timer = false; + pct->expiry_active = false; } /* @@ -1000,77 +1014,60 @@ static void check_process_timers(struct task_struct *tsk, */ 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; - struct task_struct *p = timer->it.cpu.task; u64 now; - WARN_ON_ONCE(p == NULL); + rcu_read_lock(); + p = cpu_timer_task_rcu(timer); + if (!p) + goto out; + + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) + goto out; /* * Fetch the current sample and update the timer's expiry time. */ - if (CPUCLOCK_PERTHREAD(timer->it_clock)) { - cpu_clock_sample(timer->it_clock, p, &now); - bump_cpu_timer(timer, now); - if (unlikely(p->exit_state)) - return; + if (CPUCLOCK_PERTHREAD(timer->it_clock)) + now = cpu_clock_sample(clkid, p); + else + now = cpu_clock_sample_group(clkid, p, true); - /* 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. */ - } + bump_cpu_timer(timer, now); /* * Now re-arm for the new expiry time. */ - arm_timer(timer); -unlock: + arm_timer(timer, p); unlock_task_sighand(p, &flags); +out: + rcu_read_unlock(); } /** - * task_cputime_expired - Compare two task_cputime entities. + * task_cputimers_expired - Check whether posix CPU timers are expired * - * @sample: The task_cputime structure to be checked for expiration. - * @expires: Expiration times, against which @sample will be checked. + * @samples: Array of current samples for the CPUCLOCK clocks + * @pct: Pointer to a posix_cputimers container * - * 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. + * Returns true if any member of @samples is greater than the corresponding + * member of @pct->bases[CLK].nextevt. False otherwise */ -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; +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; } /** @@ -1083,83 +1080,279 @@ static inline int task_cputime_expired(const struct task_cputime *sample, * 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) +static inline bool fastpath_timer_check(struct task_struct *tsk) { + struct posix_cputimers *pct = &tsk->posix_cputimers; struct signal_struct *sig; - if (!task_cputime_zero(&tsk->cputime_expires)) { - struct task_cputime task_sample; + if (!expiry_cache_is_inactive(pct)) { + u64 samples[CPUCLOCK_MAX]; - 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; + 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 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. + * 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 '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. + * 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(sig->cputimer.running) && - !READ_ONCE(sig->cputimer.checking_timer)) { - struct task_cputime group_sample; + if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) { + u64 samples[CPUCLOCK_MAX]; - sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic); + proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, + samples); - if (task_cputime_expired(&group_sample, &sig->cputime_expires)) - return 1; + if (task_cputimers_expired(samples, pct)) + return true; } if (dl_task(tsk) && tsk->dl.dl_overrun) - return 1; + return true; - return 0; + 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) +{ + struct posix_cputimers_work *cw = container_of(work, typeof(*cw), work); + + mutex_lock(&cw->mutex); + handle_posix_cpu_timers(current); + mutex_unlock(&cw->mutex); } /* - * 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. + * Invoked from the posix-timer core when a cancel operation failed because + * the timer is marked firing. The caller holds rcu_read_lock(), which + * protects the timer and the task which is expiring it from being freed. */ -void run_posix_cpu_timers(struct task_struct *tsk) +static void posix_cpu_timer_wait_running(struct k_itimer *timr) { - LIST_HEAD(firing); - struct k_itimer *timer, *next; - unsigned long flags; + struct task_struct *tsk = rcu_dereference(timr->it.cpu.handling); - lockdep_assert_irqs_disabled(); + /* Has the handling task completed expiry already? */ + if (!tsk) + return; + /* Ensure that the task cannot go away */ + get_task_struct(tsk); + /* Now drop the RCU protection so the mutex can be locked */ + rcu_read_unlock(); + /* Wait on the expiry mutex */ + mutex_lock(&tsk->posix_cputimers_work.mutex); + /* Release it immediately again. */ + mutex_unlock(&tsk->posix_cputimers_work.mutex); + /* Drop the task reference. */ + put_task_struct(tsk); + /* Relock RCU so the callsite is balanced */ + rcu_read_lock(); +} + +static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr) +{ + /* Ensure that timr->it.cpu.handling task cannot go away */ + rcu_read_lock(); + spin_unlock_irq(&timr->it_lock); + posix_cpu_timer_wait_running(timr); + rcu_read_unlock(); + /* @timr is on stack and is valid */ + spin_lock_irq(&timr->it_lock); +} + +/* + * Clear existing posix CPU timers task work. + */ +void clear_posix_cputimers_work(struct task_struct *p) +{ /* - * The fast path checks that there are no expired thread or thread - * group timers. If that's so, just return. + * A copied work entry from the old task is not meaningful, clear it. + * N.B. init_task_work will not do this. */ - if (!fastpath_timer_check(tsk)) - return; + memset(&p->posix_cputimers_work.work, 0, + sizeof(p->posix_cputimers_work.work)); + init_task_work(&p->posix_cputimers_work.work, + posix_cpu_timers_work); + mutex_init(&p->posix_cputimers_work.mutex); + p->posix_cputimers_work.scheduled = false; +} - if (!lock_task_sighand(tsk, &flags)) +/* + * 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) +{ + clear_posix_cputimers_work(current); +} + +/* + * 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; + } + /* - * 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. + * 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. */ - check_thread_timers(tsk, &firing); + 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 void posix_cpu_timer_wait_running(struct k_itimer *timr) +{ + cpu_relax(); +} + +static void posix_cpu_timer_wait_running_nsleep(struct k_itimer *timr) +{ + spin_unlock_irq(&timr->it_lock); + cpu_relax(); + spin_lock_irq(&timr->it_lock); +} - check_process_timers(tsk, &firing); +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 these locks before taking any timer's lock. + * 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 @@ -1174,38 +1367,86 @@ void run_posix_cpu_timers(struct task_struct *tsk) * 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; + list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) { + bool 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.entry); + list_del_init(&timer->it.cpu.elist); cpu_firing = timer->it.cpu.firing; - timer->it.cpu.firing = 0; + timer->it.cpu.firing = false; /* - * 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 the firing flag is cleared then this raced with a + * timer rearm/delete operation. So don't generate an + * event. */ - if (likely(cpu_firing >= 0)) + if (likely(cpu_firing)) cpu_timer_fire(timer); + /* See posix_cpu_timer_wait_running() */ + rcu_assign_pointer(timer->it.cpu.handling, NULL); 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(); + + /* + * Ensure that release_task(tsk) can't happen while + * handle_posix_cpu_timers() is running. Otherwise, a concurrent + * posix_cpu_timer_del() may fail to lock_task_sighand(tsk) and + * miss timer->it.cpu.firing != 0. + */ + if (tsk->exit_state) + return; + + /* + * 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 clock_idx, +void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid, u64 *newval, u64 *oldval) { - u64 now; - int ret; + u64 now, *nextevt; - WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED); - ret = cpu_timer_sample_group(clock_idx, tsk, &now); + if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED)) + return; - if (oldval && ret != -EINVAL) { + 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 @@ -1220,27 +1461,18 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, } } - if (!*newval) - return; - *newval += now; + if (*newval) + *newval += now; } /* - * Update expiration cache if we are the earliest timer, or eventually - * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire. + * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF + * expiry cache is also used by RLIMIT_CPU!. */ - 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; - } + if (*newval < *nextevt) + *nextevt = *newval; - tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER); + tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER); } static int do_cpu_nanosleep(const clockid_t which_clock, int flags, @@ -1260,6 +1492,8 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, timer.it_overrun = -1; error = posix_cpu_timer_create(&timer); timer.it_process = current; + timer.it.cpu.nanosleep = true; + if (!error) { static struct itimerspec64 zero_it; struct restart_block *restart; @@ -1275,7 +1509,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, } while (!signal_pending(current)) { - if (timer.it.cpu.expires == 0) { + if (!cpu_timer_getexpires(&timer.it.cpu)) { /* * Our timer fired and was reset, below * deletion can not fail. @@ -1297,26 +1531,19 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, /* * We were interrupted by a signal. */ - expires = timer.it.cpu.expires; + 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. - */ + /* Timer is now unarmed, deletion can not fail. */ posix_cpu_timer_del(&timer); + } else { + while (error == TIMER_RETRY) { + posix_cpu_timer_wait_running_nsleep(&timer); + error = 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); - } + spin_unlock_irq(&timer.it_lock); if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) { /* @@ -1330,7 +1557,7 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags, * Report back to the user the time still remaining. */ restart = ¤t->restart_block; - restart->nanosleep.expires = expires; + restart->nanosleep.expires = ns_to_ktime(expires); if (restart->nanosleep.type != TT_NONE) error = nanosleep_copyout(restart, &it.it_value); } @@ -1361,8 +1588,8 @@ static int posix_cpu_nsleep(const clockid_t which_clock, int flags, if (flags & TIMER_ABSTIME) return -ERESTARTNOHAND; - restart_block->fn = posix_cpu_nsleep_restart; restart_block->nanosleep.clockid = which_clock; + set_restart_fn(restart_block, posix_cpu_nsleep_restart); } return error; } @@ -1372,7 +1599,7 @@ 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); + t = ktime_to_timespec64(restart_block->nanosleep.expires); return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t); } @@ -1417,26 +1644,27 @@ static int thread_cpu_timer_create(struct k_itimer *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, + .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, + .timer_wait_running = posix_cpu_timer_wait_running, }; 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, + .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 = thread_cpu_clock_get, - .timer_create = thread_cpu_timer_create, + .clock_getres = thread_cpu_clock_getres, + .clock_get_timespec = thread_cpu_clock_get, + .timer_create = thread_cpu_timer_create, }; |