Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core timer updates from Thomas Gleixner:
 "Timers and timekeeping updates:

   - A large overhaul of the posix CPU timer code which is a preparation
     for moving the CPU timer expiry out into task work so it can be
     properly accounted on the task/process.

     An update to the bogus permission checks will come later during the
     merge window as feedback was not complete before heading of for
     travel.

   - Switch the timerqueue code to use cached rbtrees and get rid of the
     homebrewn caching of the leftmost node.

   - Consolidate hrtimer_init() + hrtimer_init_sleeper() calls into a
     single function

   - Implement the separation of hrtimers to be forced to expire in hard
     interrupt context even when PREEMPT_RT is enabled and mark the
     affected timers accordingly.

   - Implement a mechanism for hrtimers and the timer wheel to protect
     RT against priority inversion and live lock issues when a (hr)timer
     which should be canceled is currently executing the callback.
     Instead of infinitely spinning, the task which tries to cancel the
     timer blocks on a per cpu base expiry lock which is held and
     released by the (hr)timer expiry code.

   - Enable the Hyper-V TSC page based sched_clock for Hyper-V guests
     resulting in faster access to timekeeping functions.

   - Updates to various clocksource/clockevent drivers and their device
     tree bindings.

   - The usual small improvements all over the place"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits)
  posix-cpu-timers: Fix permission check regression
  posix-cpu-timers: Always clear head pointer on dequeue
  hrtimer: Add a missing bracket and hide `migration_base' on !SMP
  posix-cpu-timers: Make expiry_active check actually work correctly
  posix-timers: Unbreak CONFIG_POSIX_TIMERS=n build
  tick: Mark sched_timer to expire in hard interrupt context
  hrtimer: Add kernel doc annotation for HRTIMER_MODE_HARD
  x86/hyperv: Hide pv_ops access for CONFIG_PARAVIRT=n
  posix-cpu-timers: Utilize timerqueue for storage
  posix-cpu-timers: Move state tracking to struct posix_cputimers
  posix-cpu-timers: Deduplicate rlimit handling
  posix-cpu-timers: Remove pointless comparisons
  posix-cpu-timers: Get rid of 64bit divisions
  posix-cpu-timers: Consolidate timer expiry further
  posix-cpu-timers: Get rid of zero checks
  rlimit: Rewrite non-sensical RLIMIT_CPU comment
  posix-cpu-timers: Respect INFINITY for hard RTTIME limit
  posix-cpu-timers: Switch thread group sampling to array
  posix-cpu-timers: Restructure expiry array
  posix-cpu-timers: Remove cputime_expires
  ...

1 files changed, 492 insertions, 518 deletions

diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 0a426f4e3125..92a431981b1c 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -20,11 +20,20 @@
 
 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.
  */
 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
 {
@@ -35,46 +44,97 @@ void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
         spin_unlock_irq(&task->sighand->siglock);
 }
 
-static int check_clock(const clockid_t which_clock)
+/*
+ * Functions for validating access to tasks.
+ */
+static struct task_struct *lookup_task(const pid_t pid, bool thread,
+                                       bool gettime)
 {
-        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;
+        /*
+         * If the encoded PID is 0, then the timer is targeted at current
+         * or the process to which current belongs.
+         */
+        if (!pid)
+                return thread ? current : current->group_leader;
 
-        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;
+        if (!p)
+                return p;
+
+        if (thread)
+                return same_thread_group(p, current) ? p : NULL;
+
+        if (gettime) {
+                /*
+                 * For clock_gettime(PROCESS) the task does not need to be
+                 * the actual group leader. tsk->sighand gives
+                 * access to the group's clock.
+                 *
+                 * Timers need the group leader because they take a
+                 * reference on it and store the task pointer until the
+                 * timer is destroyed.
+                 */
+                return (p == current || thread_group_leader(p)) ? p : NULL;
         }
+
+        /*
+         * For processes require that p is group leader.
+         */
+        return has_group_leader_pid(p) ? p : NULL;
+}
+
+static struct task_struct *__get_task_for_clock(const clockid_t clock,
+                                                bool getref, bool gettime)
+{
+        const bool thread = !!CPUCLOCK_PERTHREAD(clock);
+        const pid_t pid = CPUCLOCK_PID(clock);
+        struct task_struct *p;
+
+        if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
+                return NULL;
+
+        rcu_read_lock();
+        p = lookup_task(pid, thread, gettime);
+        if (p && getref)
+                get_task_struct(p);
         rcu_read_unlock();
+        return p;
+}
 
-        return error;
+static inline struct task_struct *get_task_for_clock(const clockid_t clock)
+{
+        return __get_task_for_clock(clock, true, false);
+}
+
+static inline struct task_struct *get_task_for_clock_get(const clockid_t clock)
+{
+        return __get_task_for_clock(clock, true, true);
+}
+
+static inline int validate_clock_permissions(const clockid_t clock)
+{
+        return __get_task_for_clock(clock, false, false) ? 0 : -EINVAL;
 }
 
 /*
  * 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_interval)
-                return;
+                return expires;
 
-        if (now < timer->it.cpu.expires)
-                return;
+        if (now < expires)
+                return expires;
 
         incr = timer->it_interval;
-        delta = now + incr - timer->it.cpu.expires;
+        delta = now + incr - expires;
 
         /* Don't use (incr*2 < delta), incr*2 might overflow. */
         for (i = 0; incr < delta - incr; i++)
@@ -84,48 +144,26 @@ 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)
+/* 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)
 {
-        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;
+        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);
@@ -142,42 +180,66 @@ 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.
@@ -193,29 +255,56 @@ retry:
         }
 }
 
-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
+ * @iimes:      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 accouting 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;
 
         /* 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 +314,69 @@ 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.  Task's sighand lock must be
+ * held to protect the task traversal on a full update. 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_unlock();
-        }
+        tsk = get_task_for_clock_get(clock);
+        if (!tsk)
+                return -EINVAL;
 
-        return err;
+        if (CPUCLOCK_PERTHREAD(clock))
+                t = cpu_clock_sample(clkid, tsk);
+        else
+                t = cpu_clock_sample_group(clkid, tsk, false);
+        put_task_struct(tsk);
+
+        *tp = ns_to_timespec64(t);
+        return 0;
 }
 
 /*
@@ -322,44 +386,15 @@ 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;
+        struct task_struct *p = get_task_for_clock(new_timer->it_clock);
 
-        if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
+        if (!p)
                 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;
-                }
-        }
+        timerqueue_init(&new_timer->it.cpu.node);
         new_timer->it.cpu.task = p;
-        if (p) {
-                get_task_struct(p);
-        } else {
-                ret = -EINVAL;
-        }
-        rcu_read_unlock();
-
-        return ret;
+        return 0;
 }
 
 /*
@@ -370,12 +405,14 @@ 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 task_struct *p = ctmr->task;
         struct sighand_struct *sighand;
-        struct task_struct *p = timer->it.cpu.task;
+        unsigned long flags;
+        int ret = 0;
 
-        WARN_ON_ONCE(p == NULL);
+        if (WARN_ON_ONCE(!p))
+                return -EINVAL;
 
         /*
          * Protect against sighand release/switch in exit/exec and process/
@@ -384,15 +421,15 @@ 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)
                         ret = TIMER_RETRY;
                 else
-                        list_del(&timer->it.cpu.entry);
+                        cpu_timer_dequeue(ctmr);
 
                 unlock_task_sighand(p, &flags);
         }
@@ -403,25 +440,30 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
         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);
 }
 
 /*
@@ -431,16 +473,11 @@ 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);
 }
 
 /*
@@ -449,58 +486,33 @@ static inline int expires_gt(u64 expires, u64 new_exp)
  */
 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;
+        int clkidx = CPUCLOCK_WHICH(timer->it_clock);
+        struct cpu_timer *ctmr = &timer->it.cpu;
+        u64 newexp = cpu_timer_getexpires(ctmr);
+        struct task_struct *p = ctmr->task;
+        struct posix_cputimer_base *base;
+
+        if (CPUCLOCK_PERTHREAD(timer->it_clock))
+                base = p->posix_cputimers.bases + clkidx;
+        else
+                base = p->signal->posix_cputimers.bases + clkidx;
+
+        if (!cpu_timer_enqueue(&base->tqhead, ctmr))
+                return;
 
-                /*
-                 * We are the new earliest-expiring POSIX 1.b timer, hence
-                 * need to update expiration cache. Take into account that
-                 * for process timers we share expiration cache with itimers
-                 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
-                 */
+        /*
+         * 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->signal, TICK_DEP_BIT_POSIX_TIMER);
 }
 
 /*
@@ -508,24 +520,26 @@ static void arm_timer(struct k_itimer *timer)
  */
 static void cpu_timer_fire(struct k_itimer *timer)
 {
+        struct cpu_timer *ctmr = &timer->it.cpu;
+
         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
                 /*
                  * User don't want any signal.
                  */
-                timer->it.cpu.expires = 0;
+                cpu_timer_setexpires(ctmr, 0);
         } else if (unlikely(timer->sigq == NULL)) {
                 /*
                  * This a special case for clock_nanosleep,
                  * not a normal timer from sys_timer_create.
                  */
                 wake_up_process(timer->it_process);
-                timer->it.cpu.expires = 0;
+                cpu_timer_setexpires(ctmr, 0);
         } else if (!timer->it_interval) {
                 /*
                  * One-shot timer.  Clear it as soon as it's fired.
                  */
                 posix_timer_event(timer, 0);
-                timer->it.cpu.expires = 0;
+                cpu_timer_setexpires(ctmr, 0);
         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
                 /*
                  * The signal did not get queued because the signal
@@ -539,33 +553,6 @@ static void cpu_timer_fire(struct k_itimer *timer)
 }
 
 /*
- * Sample a process (thread group) timer for the given group_leader task.
- * Must be called with task sighand lock held for safe while_each_thread()
- * traversal.
- */
-static int cpu_timer_sample_group(const clockid_t which_clock,
-                                  struct task_struct *p, 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
@@ -574,13 +561,16 @@ 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;
-        struct sighand_struct *sighand;
-        struct task_struct *p = timer->it.cpu.task;
+        clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
         u64 old_expires, new_expires, old_incr, val;
-        int ret;
+        struct cpu_timer *ctmr = &timer->it.cpu;
+        struct task_struct *p = ctmr->task;
+        struct sighand_struct *sighand;
+        unsigned long flags;
+        int ret = 0;
 
-        WARN_ON_ONCE(p == NULL);
+        if (WARN_ON_ONCE(!p))
+                return -EINVAL;
 
         /*
          * Use the to_ktime conversion because that clamps the maximum
@@ -597,22 +587,21 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
          * If p has just been reaped, we can no
          * longer get any information about it at all.
          */
-        if (unlikely(sighand == NULL)) {
+        if (unlikely(sighand == NULL))
                 return -ESRCH;
-        }
 
         /*
          * Disarm any old timer after extracting its expiry time.
          */
-
-        ret = 0;
         old_incr = timer->it_interval;
-        old_expires = timer->it.cpu.expires;
+        old_expires = cpu_timer_getexpires(ctmr);
+
         if (unlikely(timer->it.cpu.firing)) {
                 timer->it.cpu.firing = -1;
                 ret = TIMER_RETRY;
-        } else
-                list_del_init(&timer->it.cpu.entry);
+        } else {
+                cpu_timer_dequeue(ctmr);
+        }
 
         /*
          * We need to sample the current value to convert the new
@@ -622,11 +611,10 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
          * 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 (CPUCLOCK_PERTHREAD(timer->it_clock))
+                val = cpu_clock_sample(clkid, p);
+        else
+                val = cpu_clock_sample_group(clkid, p, true);
 
         if (old) {
                 if (old_expires == 0) {
@@ -634,18 +622,16 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
                         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.
+                         * 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;
+                        u64 exp = bump_cpu_timer(timer, val);
+
+                        if (val < exp) {
+                                old_expires = exp - val;
                                 old->it_value = ns_to_timespec64(old_expires);
                         } else {
                                 old->it_value.tv_nsec = 1;
@@ -674,7 +660,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
          * 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;
+        cpu_timer_setexpires(ctmr, new_expires);
         if (new_expires != 0 && val < new_expires) {
                 arm_timer(timer);
         }
@@ -715,24 +701,27 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 
 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
 {
-        u64 now;
-        struct task_struct *p = timer->it.cpu.task;
+        clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
+        struct cpu_timer *ctmr = &timer->it.cpu;
+        u64 now, expires = cpu_timer_getexpires(ctmr);
+        struct task_struct *p = ctmr->task;
 
-        WARN_ON_ONCE(p == NULL);
+        if (WARN_ON_ONCE(!p))
+                return;
 
         /*
          * Easy part: convert the reload time.
          */
         itp->it_interval = ktime_to_timespec64(timer->it_interval);
 
-        if (!timer->it.cpu.expires)
+        if (!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);
+                now = cpu_clock_sample(clkid, p);
         } else {
                 struct sighand_struct *sighand;
                 unsigned long flags;
@@ -747,18 +736,18 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
                         /*
                          * The process has been reaped.
                          * We can't even collect a sample any more.
-                         * Call the timer disarmed, nothing else to do.
+                         * Disarm the timer, nothing else to do.
                          */
-                        timer->it.cpu.expires = 0;
+                        cpu_timer_setexpires(ctmr, 0);
                         return;
                 } else {
-                        cpu_timer_sample_group(timer->it_clock, p, &now);
+                        now = cpu_clock_sample_group(clkid, p, false);
                         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
@@ -769,26 +758,42 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp
         }
 }
 
-static unsigned long long
-check_timers_list(struct list_head *timers,
-                  struct list_head *firing,
-                  unsigned long long curr)
-{
-        int maxfire = 20;
+#define MAX_COLLECTED   20
 
-        while (!list_empty(timers)) {
-                struct cpu_timer_list *t;
+static u64 collect_timerqueue(struct timerqueue_head *head,
+                              struct list_head *firing, u64 now)
+{
+        struct timerqueue_node *next;
+        int i = 0;
+
+        while ((next = timerqueue_getnext(head))) {
+                struct cpu_timer *ctmr;
+                u64 expires;
+
+                ctmr = container_of(next, struct cpu_timer, node);
+                expires = cpu_timer_getexpires(ctmr);
+                /* Limit the number of timers to expire at once */
+                if (++i == MAX_COLLECTED || now < expires)
+                        return expires;
+
+                ctmr->firing = 1;
+                cpu_timer_dequeue(ctmr);
+                list_add_tail(&ctmr->elist, firing);
+        }
 
-                t = list_first_entry(timers, struct cpu_timer_list, entry);
+        return U64_MAX;
+}
 
-                if (!--maxfire || curr < t->expires)
-                        return t->expires;
+static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
+                                    struct list_head *firing)
+{
+        struct posix_cputimer_base *base = pct->bases;
+        int i;
 
-                t->firing = 1;
-                list_move_tail(&t->entry, firing);
+        for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
+                base->nextevt = collect_timerqueue(&base->tqhead, firing,
+                                                    samples[i]);
         }
-
-        return 0;
 }
 
 static inline void check_dl_overrun(struct task_struct *tsk)
@@ -799,6 +804,20 @@ static inline void check_dl_overrun(struct task_struct *tsk)
         }
 }
 
+static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
+{
+        if (time < limit)
+                return false;
+
+        if (print_fatal_signals) {
+                pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
+                        rt ? "RT" : "CPU", hard ? "hard" : "soft",
+                        current->comm, task_pid_nr(current));
+        }
+        __group_send_sig_info(signo, SEND_SIG_PRIV, current);
+        return true;
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them off
  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
@@ -807,76 +826,50 @@ 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);
 }
 
@@ -898,7 +891,7 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
                 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
         }
 
-        if (it->expires && (!*expires || it->expires < *expires))
+        if (it->expires && it->expires < *expires)
                 *expires = it->expires;
 }
 
@@ -911,87 +904,69 @@ 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;
 }
 
 /*
@@ -1000,18 +975,21 @@ 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 cpu_timer *ctmr = &timer->it.cpu;
+        struct task_struct *p = ctmr->task;
         struct sighand_struct *sighand;
         unsigned long flags;
-        struct task_struct *p = timer->it.cpu.task;
         u64 now;
 
-        WARN_ON_ONCE(p == NULL);
+        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);
+                now = cpu_clock_sample(clkid, p);
                 bump_cpu_timer(timer, now);
                 if (unlikely(p->exit_state))
                         return;
@@ -1031,13 +1009,13 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer)
                          * The process has been reaped.
                          * We can't even collect a sample any more.
                          */
-                        timer->it.cpu.expires = 0;
+                        cpu_timer_setexpires(ctmr, 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);
+                now = cpu_clock_sample_group(clkid, p, true);
                 bump_cpu_timer(timer, now);
                 /* Leave the sighand locked for the call below.  */
         }
@@ -1051,26 +1029,24 @@ 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)
+static inline bool
+task_cputimers_expired(const u64 *sample, struct posix_cputimers *pct)
 {
-        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;
+        int i;
+
+        for (i = 0; i < CPUCLOCK_MAX; i++) {
+                if (sample[i] >= pct->bases[i].nextevt)
+                        return true;
+        }
+        return false;
 }
 
 /**
@@ -1083,48 +1059,50 @@ 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;
 }
 
 /*
@@ -1132,11 +1110,12 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
  * 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)
+void run_posix_cpu_timers(void)
 {
-        LIST_HEAD(firing);
+        struct task_struct *tsk = current;
         struct k_itimer *timer, *next;
         unsigned long flags;
+        LIST_HEAD(firing);
 
         lockdep_assert_irqs_disabled();
 
@@ -1174,11 +1153,11 @@ 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) {
+        list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
                 int cpu_firing;
 
                 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;
                 /*
@@ -1196,16 +1175,18 @@ void run_posix_cpu_timers(struct task_struct *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;
+
+        if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
+                return;
 
-        WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED);
-        ret = cpu_timer_sample_group(clock_idx, tsk, &now);
+        nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
+        now = cpu_clock_sample_group(clkid, tsk, true);
 
-        if (oldval && ret != -EINVAL) {
+        if (oldval) {
                 /*
                  * We are setting itimer. The *oldval is absolute and we update
                  * it to be relative, *newval argument is relative and we update
@@ -1226,19 +1207,11 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
         }
 
         /*
-         * 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);
 }
@@ -1260,6 +1233,7 @@ 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;
+
         if (!error) {
                 static struct itimerspec64 zero_it;
                 struct restart_block *restart;
@@ -1275,7 +1249,7 @@ 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.
@@ -1297,7 +1271,7 @@ 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) {
                         /*