ftrace: Update the kconfig for DYNAMIC_FTRACE
[linux-2.6.git] / kernel / posix-cpu-timers.c
index b15462b..acbb79c 100644 (file)
@@ -4,10 +4,28 @@
 
 #include <linux/sched.h>
 #include <linux/posix-timers.h>
-#include <asm/uaccess.h>
 #include <linux/errno.h>
+#include <linux/math64.h>
+#include <asm/uaccess.h>
+#include <linux/kernel_stat.h>
+#include <trace/events/timer.h>
+
+/*
+ * Called after updating RLIMIT_CPU to run cpu timer and update
+ * tsk->signal->cputime_expires expiration cache if necessary. Needs
+ * siglock protection since other code may update expiration cache as
+ * well.
+ */
+void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
+{
+       cputime_t cputime = secs_to_cputime(rlim_new);
 
-static int check_clock(clockid_t which_clock)
+       spin_lock_irq(&task->sighand->siglock);
+       set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
+       spin_unlock_irq(&task->sighand->siglock);
+}
+
+static int check_clock(const clockid_t which_clock)
 {
        int error = 0;
        struct task_struct *p;
@@ -19,70 +37,68 @@ static int check_clock(clockid_t which_clock)
        if (pid == 0)
                return 0;
 
-       read_lock(&tasklist_lock);
-       p = find_task_by_pid(pid);
-       if (!p || (CPUCLOCK_PERTHREAD(which_clock) ?
-                  p->tgid != current->tgid : p->tgid != pid)) {
+       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;
        }
-       read_unlock(&tasklist_lock);
+       rcu_read_unlock();
 
        return error;
 }
 
 static inline union cpu_time_count
-timespec_to_sample(clockid_t which_clock, const struct timespec *tp)
+timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
 {
        union cpu_time_count ret;
        ret.sched = 0;          /* high half always zero when .cpu used */
        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-               ret.sched = tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
+               ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
        } else {
                ret.cpu = timespec_to_cputime(tp);
        }
        return ret;
 }
 
-static void sample_to_timespec(clockid_t which_clock,
+static void sample_to_timespec(const clockid_t which_clock,
                               union cpu_time_count cpu,
                               struct timespec *tp)
 {
-       if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
-               tp->tv_sec = div_long_long_rem(cpu.sched,
-                                              NSEC_PER_SEC, &tp->tv_nsec);
-       } else {
+       if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
+               *tp = ns_to_timespec(cpu.sched);
+       else
                cputime_to_timespec(cpu.cpu, tp);
-       }
 }
 
-static inline int cpu_time_before(clockid_t which_clock,
+static inline int cpu_time_before(const clockid_t which_clock,
                                  union cpu_time_count now,
                                  union cpu_time_count then)
 {
        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
                return now.sched < then.sched;
        }  else {
-               return cputime_lt(now.cpu, then.cpu);
+               return now.cpu < then.cpu;
        }
 }
-static inline void cpu_time_add(clockid_t which_clock,
+static inline void cpu_time_add(const clockid_t which_clock,
                                union cpu_time_count *acc,
                                union cpu_time_count val)
 {
        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
                acc->sched += val.sched;
        }  else {
-               acc->cpu = cputime_add(acc->cpu, val.cpu);
+               acc->cpu += val.cpu;
        }
 }
-static inline union cpu_time_count cpu_time_sub(clockid_t which_clock,
+static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
                                                union cpu_time_count a,
                                                union cpu_time_count b)
 {
        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
                a.sched -= b.sched;
        }  else {
-               a.cpu = cputime_sub(a.cpu, b.cpu);
+               a.cpu -= b.cpu;
        }
        return a;
 }
@@ -91,7 +107,7 @@ static inline union cpu_time_count cpu_time_sub(clockid_t which_clock,
  * Update expiry time from increment, and increase overrun count,
  * given the current clock sample.
  */
-static inline void bump_cpu_timer(struct k_itimer *timer,
+static void bump_cpu_timer(struct k_itimer *timer,
                                  union cpu_time_count now)
 {
        int i;
@@ -110,7 +126,7 @@ static inline void bump_cpu_timer(struct k_itimer *timer,
                for (i = 0; incr < delta - incr; i++)
                        incr = incr << 1;
                for (; i >= 0; incr >>= 1, i--) {
-                       if (delta <= incr)
+                       if (delta < incr)
                                continue;
                        timer->it.cpu.expires.sched += incr;
                        timer->it_overrun += 1 << i;
@@ -119,39 +135,34 @@ static inline void bump_cpu_timer(struct k_itimer *timer,
        } else {
                cputime_t delta, incr;
 
-               if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
+               if (now.cpu < timer->it.cpu.expires.cpu)
                        return;
                incr = timer->it.cpu.incr.cpu;
-               delta = cputime_sub(cputime_add(now.cpu, incr),
-                                   timer->it.cpu.expires.cpu);
+               delta = now.cpu + incr - timer->it.cpu.expires.cpu;
                /* Don't use (incr*2 < delta), incr*2 might overflow. */
-               for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
-                            incr = cputime_add(incr, incr);
-               for (; i >= 0; incr = cputime_halve(incr), i--) {
-                       if (cputime_le(delta, incr))
+               for (i = 0; incr < delta - incr; i++)
+                            incr += incr;
+               for (; i >= 0; incr = incr >> 1, i--) {
+                       if (delta < incr)
                                continue;
-                       timer->it.cpu.expires.cpu =
-                               cputime_add(timer->it.cpu.expires.cpu, incr);
+                       timer->it.cpu.expires.cpu += incr;
                        timer->it_overrun += 1 << i;
-                       delta = cputime_sub(delta, incr);
+                       delta -= incr;
                }
        }
 }
 
 static inline cputime_t prof_ticks(struct task_struct *p)
 {
-       return cputime_add(p->utime, p->stime);
+       return p->utime + p->stime;
 }
 static inline cputime_t virt_ticks(struct task_struct *p)
 {
        return p->utime;
 }
-static inline unsigned long long sched_ns(struct task_struct *p)
-{
-       return (p == current) ? current_sched_time(p) : p->sched_time;
-}
 
-int posix_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
+static int
+posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 {
        int error = check_clock(which_clock);
        if (!error) {
@@ -169,7 +180,8 @@ int posix_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
        return error;
 }
 
-int posix_cpu_clock_set(clockid_t which_clock, const struct timespec *tp)
+static int
+posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 {
        /*
         * You can never reset a CPU clock, but we check for other errors
@@ -186,7 +198,7 @@ int posix_cpu_clock_set(clockid_t which_clock, const struct timespec *tp)
 /*
  * Sample a per-thread clock for the given task.
  */
-static int cpu_clock_sample(clockid_t which_clock, struct task_struct *p,
+static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
                            union cpu_time_count *cpu)
 {
        switch (CPUCLOCK_WHICH(which_clock)) {
@@ -199,81 +211,102 @@ static int cpu_clock_sample(clockid_t which_clock, struct task_struct *p,
                cpu->cpu = virt_ticks(p);
                break;
        case CPUCLOCK_SCHED:
-               cpu->sched = sched_ns(p);
+               cpu->sched = task_sched_runtime(p);
                break;
        }
        return 0;
 }
 
+void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
+{
+       struct signal_struct *sig = tsk->signal;
+       struct task_struct *t;
+
+       times->utime = sig->utime;
+       times->stime = sig->stime;
+       times->sum_exec_runtime = sig->sum_sched_runtime;
+
+       rcu_read_lock();
+       /* make sure we can trust tsk->thread_group list */
+       if (!likely(pid_alive(tsk)))
+               goto out;
+
+       t = tsk;
+       do {
+               times->utime += t->utime;
+               times->stime += t->stime;
+               times->sum_exec_runtime += task_sched_runtime(t);
+       } while_each_thread(tsk, t);
+out:
+       rcu_read_unlock();
+}
+
+static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
+{
+       if (b->utime > a->utime)
+               a->utime = b->utime;
+
+       if (b->stime > a->stime)
+               a->stime = b->stime;
+
+       if (b->sum_exec_runtime > a->sum_exec_runtime)
+               a->sum_exec_runtime = b->sum_exec_runtime;
+}
+
+void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
+{
+       struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+       struct task_cputime sum;
+       unsigned long flags;
+
+       if (!cputimer->running) {
+               /*
+                * The POSIX timer interface allows for absolute time expiry
+                * values through the TIMER_ABSTIME flag, therefore we have
+                * to synchronize the timer to the clock every time we start
+                * it.
+                */
+               thread_group_cputime(tsk, &sum);
+               raw_spin_lock_irqsave(&cputimer->lock, flags);
+               cputimer->running = 1;
+               update_gt_cputime(&cputimer->cputime, &sum);
+       } else
+               raw_spin_lock_irqsave(&cputimer->lock, flags);
+       *times = cputimer->cputime;
+       raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+}
+
 /*
  * Sample a process (thread group) clock for the given group_leader task.
  * Must be called with tasklist_lock held for reading.
- * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
  */
-static int cpu_clock_sample_group_locked(unsigned int clock_idx,
-                                        struct task_struct *p,
-                                        union cpu_time_count *cpu)
+static int cpu_clock_sample_group(const clockid_t which_clock,
+                                 struct task_struct *p,
+                                 union cpu_time_count *cpu)
 {
-       struct task_struct *t = p;
-       switch (clock_idx) {
+       struct task_cputime cputime;
+
+       switch (CPUCLOCK_WHICH(which_clock)) {
        default:
                return -EINVAL;
        case CPUCLOCK_PROF:
-               cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
-               do {
-                       cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
-                       t = next_thread(t);
-               } while (t != p);
+               thread_group_cputime(p, &cputime);
+               cpu->cpu = cputime.utime + cputime.stime;
                break;
        case CPUCLOCK_VIRT:
-               cpu->cpu = p->signal->utime;
-               do {
-                       cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
-                       t = next_thread(t);
-               } while (t != p);
+               thread_group_cputime(p, &cputime);
+               cpu->cpu = cputime.utime;
                break;
        case CPUCLOCK_SCHED:
-               cpu->sched = p->signal->sched_time;
-               /* Add in each other live thread.  */
-               while ((t = next_thread(t)) != p) {
-                       cpu->sched += t->sched_time;
-               }
-               if (p->tgid == current->tgid) {
-                       /*
-                        * We're sampling ourselves, so include the
-                        * cycles not yet banked.  We still omit
-                        * other threads running on other CPUs,
-                        * so the total can always be behind as
-                        * much as max(nthreads-1,ncpus) * (NSEC_PER_SEC/HZ).
-                        */
-                       cpu->sched += current_sched_time(current);
-               } else {
-                       cpu->sched += p->sched_time;
-               }
+               thread_group_cputime(p, &cputime);
+               cpu->sched = cputime.sum_exec_runtime;
                break;
        }
        return 0;
 }
 
-/*
- * Sample a process (thread group) clock for the given group_leader task.
- * Must be called with tasklist_lock held for reading.
- */
-static int cpu_clock_sample_group(clockid_t which_clock,
-                                 struct task_struct *p,
-                                 union cpu_time_count *cpu)
-{
-       int ret;
-       unsigned long flags;
-       spin_lock_irqsave(&p->sighand->siglock, flags);
-       ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
-                                           cpu);
-       spin_unlock_irqrestore(&p->sighand->siglock, flags);
-       return ret;
-}
-
 
-int posix_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
+static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 {
        const pid_t pid = CPUCLOCK_PID(which_clock);
        int error = -EINVAL;
@@ -302,20 +335,25 @@ int posix_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
                 * should be able to see it.
                 */
                struct task_struct *p;
-               read_lock(&tasklist_lock);
-               p = find_task_by_pid(pid);
+               rcu_read_lock();
+               p = find_task_by_vpid(pid);
                if (p) {
                        if (CPUCLOCK_PERTHREAD(which_clock)) {
-                               if (p->tgid == current->tgid) {
+                               if (same_thread_group(p, current)) {
                                        error = cpu_clock_sample(which_clock,
                                                                 p, &rtn);
                                }
-                       } else if (p->tgid == pid && p->signal) {
-                               error = cpu_clock_sample_group(which_clock,
-                                                              p, &rtn);
+                       } else {
+                               read_lock(&tasklist_lock);
+                               if (thread_group_leader(p) && p->sighand) {
+                                       error =
+                                           cpu_clock_sample_group(which_clock,
+                                                                  p, &rtn);
+                               }
+                               read_unlock(&tasklist_lock);
                        }
                }
-               read_unlock(&tasklist_lock);
+               rcu_read_unlock();
        }
 
        if (error)
@@ -327,9 +365,10 @@ int posix_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
 
 /*
  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
- * This is called from sys_timer_create with the new timer already locked.
+ * This is called from sys_timer_create() and do_cpu_nanosleep() with the
+ * new timer already all-zeros initialized.
  */
-int posix_cpu_timer_create(struct k_itimer *new_timer)
+static int posix_cpu_timer_create(struct k_itimer *new_timer)
 {
        int ret = 0;
        const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
@@ -339,24 +378,22 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
                return -EINVAL;
 
        INIT_LIST_HEAD(&new_timer->it.cpu.entry);
-       new_timer->it.cpu.incr.sched = 0;
-       new_timer->it.cpu.expires.sched = 0;
 
-       read_lock(&tasklist_lock);
+       rcu_read_lock();
        if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
                if (pid == 0) {
                        p = current;
                } else {
-                       p = find_task_by_pid(pid);
-                       if (p && p->tgid != current->tgid)
+                       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_pid(pid);
-                       if (p && p->tgid != pid)
+                       p = find_task_by_vpid(pid);
+                       if (p && !has_group_leader_pid(p))
                                p = NULL;
                }
        }
@@ -366,7 +403,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
        } else {
                ret = -EINVAL;
        }
-       read_unlock(&tasklist_lock);
+       rcu_read_unlock();
 
        return ret;
 }
@@ -377,14 +414,14 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
  * If we return TIMER_RETRY, it's necessary to release the timer's lock
  * and try again.  (This happens when the timer is in the middle of firing.)
  */
-int posix_cpu_timer_del(struct k_itimer *timer)
+static int posix_cpu_timer_del(struct k_itimer *timer)
 {
        struct task_struct *p = timer->it.cpu.task;
        int ret = 0;
 
        if (likely(p != NULL)) {
                read_lock(&tasklist_lock);
-               if (unlikely(p->signal == NULL)) {
+               if (unlikely(p->sighand == NULL)) {
                        /*
                         * We raced with the reaping of the task.
                         * The deletion should have cleared us off the list.
@@ -415,39 +452,37 @@ int posix_cpu_timer_del(struct k_itimer *timer)
  */
 static void cleanup_timers(struct list_head *head,
                           cputime_t utime, cputime_t stime,
-                          unsigned long long sched_time)
+                          unsigned long long sum_exec_runtime)
 {
        struct cpu_timer_list *timer, *next;
-       cputime_t ptime = cputime_add(utime, stime);
+       cputime_t ptime = utime + stime;
 
        list_for_each_entry_safe(timer, next, head, entry) {
                list_del_init(&timer->entry);
-               if (cputime_lt(timer->expires.cpu, ptime)) {
-                       timer->expires.cpu = cputime_zero;
+               if (timer->expires.cpu < ptime) {
+                       timer->expires.cpu = 0;
                } else {
-                       timer->expires.cpu = cputime_sub(timer->expires.cpu,
-                                                        ptime);
+                       timer->expires.cpu -= ptime;
                }
        }
 
        ++head;
        list_for_each_entry_safe(timer, next, head, entry) {
                list_del_init(&timer->entry);
-               if (cputime_lt(timer->expires.cpu, utime)) {
-                       timer->expires.cpu = cputime_zero;
+               if (timer->expires.cpu < utime) {
+                       timer->expires.cpu = 0;
                } else {
-                       timer->expires.cpu = cputime_sub(timer->expires.cpu,
-                                                        utime);
+                       timer->expires.cpu -= utime;
                }
        }
 
        ++head;
        list_for_each_entry_safe(timer, next, head, entry) {
                list_del_init(&timer->entry);
-               if (timer->expires.sched < sched_time) {
+               if (timer->expires.sched < sum_exec_runtime) {
                        timer->expires.sched = 0;
                } else {
-                       timer->expires.sched -= sched_time;
+                       timer->expires.sched -= sum_exec_runtime;
                }
        }
 }
@@ -460,84 +495,16 @@ static void cleanup_timers(struct list_head *head,
 void posix_cpu_timers_exit(struct task_struct *tsk)
 {
        cleanup_timers(tsk->cpu_timers,
-                      tsk->utime, tsk->stime, tsk->sched_time);
+                      tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 
 }
 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 {
-       cleanup_timers(tsk->signal->cpu_timers,
-                      cputime_add(tsk->utime, tsk->signal->utime),
-                      cputime_add(tsk->stime, tsk->signal->stime),
-                      tsk->sched_time + tsk->signal->sched_time);
-}
-
-
-/*
- * Set the expiry times of all the threads in the process so one of them
- * will go off before the process cumulative expiry total is reached.
- */
-static void process_timer_rebalance(struct task_struct *p,
-                                   unsigned int clock_idx,
-                                   union cpu_time_count expires,
-                                   union cpu_time_count val)
-{
-       cputime_t ticks, left;
-       unsigned long long ns, nsleft;
-       struct task_struct *t = p;
-       unsigned int nthreads = atomic_read(&p->signal->live);
-
-       if (!nthreads)
-               return;
+       struct signal_struct *const sig = tsk->signal;
 
-       switch (clock_idx) {
-       default:
-               BUG();
-               break;
-       case CPUCLOCK_PROF:
-               left = cputime_div(cputime_sub(expires.cpu, val.cpu),
-                                  nthreads);
-               do {
-                       if (!unlikely(t->exit_state)) {
-                               ticks = cputime_add(prof_ticks(t), left);
-                               if (cputime_eq(t->it_prof_expires,
-                                              cputime_zero) ||
-                                   cputime_gt(t->it_prof_expires, ticks)) {
-                                       t->it_prof_expires = ticks;
-                               }
-                       }
-                       t = next_thread(t);
-               } while (t != p);
-               break;
-       case CPUCLOCK_VIRT:
-               left = cputime_div(cputime_sub(expires.cpu, val.cpu),
-                                  nthreads);
-               do {
-                       if (!unlikely(t->exit_state)) {
-                               ticks = cputime_add(virt_ticks(t), left);
-                               if (cputime_eq(t->it_virt_expires,
-                                              cputime_zero) ||
-                                   cputime_gt(t->it_virt_expires, ticks)) {
-                                       t->it_virt_expires = ticks;
-                               }
-                       }
-                       t = next_thread(t);
-               } while (t != p);
-               break;
-       case CPUCLOCK_SCHED:
-               nsleft = expires.sched - val.sched;
-               do_div(nsleft, nthreads);
-               do {
-                       if (!unlikely(t->exit_state)) {
-                               ns = t->sched_time + nsleft;
-                               if (t->it_sched_expires == 0 ||
-                                   t->it_sched_expires > ns) {
-                                       t->it_sched_expires = ns;
-                               }
-                       }
-                       t = next_thread(t);
-               } while (t != p);
-               break;
-       }
+       cleanup_timers(tsk->signal->cpu_timers,
+                      tsk->utime + sig->utime, tsk->stime + sig->stime,
+                      tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 }
 
 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
@@ -553,113 +520,67 @@ static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
                                             now);
 }
 
+static inline int expires_gt(cputime_t expires, cputime_t new_exp)
+{
+       return expires == 0 || expires > new_exp;
+}
+
 /*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
- * for reading, and interrupts disabled.
+ * for reading, interrupts disabled and p->sighand->siglock taken.
  */
-static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
+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;
-       unsigned long i;
 
-       head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
-               p->cpu_timers : p->signal->cpu_timers);
+       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);
 
-       BUG_ON(!irqs_disabled());
-       spin_lock(&p->sighand->siglock);
-
        listpos = head;
-       if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
-               list_for_each_entry(next, head, entry) {
-                       if (next->expires.sched > nt->expires.sched) {
-                               listpos = &next->entry;
-                               break;
-                       }
-               }
-       } else {
-               list_for_each_entry(next, head, entry) {
-                       if (cputime_gt(next->expires.cpu, nt->expires.cpu)) {
-                               listpos = &next->entry;
-                               break;
-                       }
-               }
+       list_for_each_entry(next, head, entry) {
+               if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
+                       break;
+               listpos = &next->entry;
        }
        list_add(&nt->entry, listpos);
 
        if (listpos == head) {
+               union cpu_time_count *exp = &nt->expires;
+
                /*
-                * We are the new earliest-expiring timer.
-                * If we are a thread timer, there can always
-                * be a process timer telling us to stop earlier.
+                * 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 (CPUCLOCK_PERTHREAD(timer->it_clock)) {
-                       switch (CPUCLOCK_WHICH(timer->it_clock)) {
-                       default:
-                               BUG();
-                       case CPUCLOCK_PROF:
-                               if (cputime_eq(p->it_prof_expires,
-                                              cputime_zero) ||
-                                   cputime_gt(p->it_prof_expires,
-                                              nt->expires.cpu))
-                                       p->it_prof_expires = nt->expires.cpu;
-                               break;
-                       case CPUCLOCK_VIRT:
-                               if (cputime_eq(p->it_virt_expires,
-                                              cputime_zero) ||
-                                   cputime_gt(p->it_virt_expires,
-                                              nt->expires.cpu))
-                                       p->it_virt_expires = nt->expires.cpu;
-                               break;
-                       case CPUCLOCK_SCHED:
-                               if (p->it_sched_expires == 0 ||
-                                   p->it_sched_expires > nt->expires.sched)
-                                       p->it_sched_expires = nt->expires.sched;
-                               break;
-                       }
-               } else {
-                       /*
-                        * For a process timer, we must balance
-                        * all the live threads' expirations.
-                        */
-                       switch (CPUCLOCK_WHICH(timer->it_clock)) {
-                       default:
-                               BUG();
-                       case CPUCLOCK_VIRT:
-                               if (!cputime_eq(p->signal->it_virt_expires,
-                                               cputime_zero) &&
-                                   cputime_lt(p->signal->it_virt_expires,
-                                              timer->it.cpu.expires.cpu))
-                                       break;
-                               goto rebalance;
-                       case CPUCLOCK_PROF:
-                               if (!cputime_eq(p->signal->it_prof_expires,
-                                               cputime_zero) &&
-                                   cputime_lt(p->signal->it_prof_expires,
-                                              timer->it.cpu.expires.cpu))
-                                       break;
-                               i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
-                               if (i != RLIM_INFINITY &&
-                                   i <= cputime_to_secs(timer->it.cpu.expires.cpu))
-                                       break;
-                               goto rebalance;
-                       case CPUCLOCK_SCHED:
-                       rebalance:
-                               process_timer_rebalance(
-                                       timer->it.cpu.task,
-                                       CPUCLOCK_WHICH(timer->it_clock),
-                                       timer->it.cpu.expires, now);
-                               break;
-                       }
+               switch (CPUCLOCK_WHICH(timer->it_clock)) {
+               case CPUCLOCK_PROF:
+                       if (expires_gt(cputime_expires->prof_exp, exp->cpu))
+                               cputime_expires->prof_exp = exp->cpu;
+                       break;
+               case CPUCLOCK_VIRT:
+                       if (expires_gt(cputime_expires->virt_exp, exp->cpu))
+                               cputime_expires->virt_exp = exp->cpu;
+                       break;
+               case CPUCLOCK_SCHED:
+                       if (cputime_expires->sched_exp == 0 ||
+                           cputime_expires->sched_exp > exp->sched)
+                               cputime_expires->sched_exp = exp->sched;
+                       break;
                }
        }
-
-       spin_unlock(&p->sighand->siglock);
 }
 
 /*
@@ -667,7 +588,12 @@ static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
  */
 static void cpu_timer_fire(struct k_itimer *timer)
 {
-       if (unlikely(timer->sigq == NULL)) {
+       if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
+               /*
+                * User don't want any signal.
+                */
+               timer->it.cpu.expires.sched = 0;
+       } else if (unlikely(timer->sigq == NULL)) {
                /*
                 * This a special case for clock_nanosleep,
                 * not a normal timer from sys_timer_create.
@@ -692,16 +618,43 @@ 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 tasklist_lock held for reading.
+ */
+static int cpu_timer_sample_group(const clockid_t which_clock,
+                                 struct task_struct *p,
+                                 union cpu_time_count *cpu)
+{
+       struct task_cputime cputime;
+
+       thread_group_cputimer(p, &cputime);
+       switch (CPUCLOCK_WHICH(which_clock)) {
+       default:
+               return -EINVAL;
+       case CPUCLOCK_PROF:
+               cpu->cpu = cputime.utime + cputime.stime;
+               break;
+       case CPUCLOCK_VIRT:
+               cpu->cpu = cputime.utime;
+               break;
+       case CPUCLOCK_SCHED:
+               cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
+               break;
+       }
+       return 0;
+}
+
+/*
  * Guts of sys_timer_settime for CPU timers.
  * This is called with the timer locked and interrupts disabled.
  * If we return TIMER_RETRY, it's necessary to release the timer's lock
  * and try again.  (This happens when the timer is in the middle of firing.)
  */
-int posix_cpu_timer_set(struct k_itimer *timer, int flags,
-                       struct itimerspec *new, struct itimerspec *old)
+static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
+                              struct itimerspec *new, struct itimerspec *old)
 {
        struct task_struct *p = timer->it.cpu.task;
-       union cpu_time_count old_expires, new_expires, val;
+       union cpu_time_count old_expires, new_expires, old_incr, val;
        int ret;
 
        if (unlikely(p == NULL)) {
@@ -716,10 +669,10 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
        read_lock(&tasklist_lock);
        /*
         * We need the tasklist_lock to protect against reaping that
-        * clears p->signal.  If p has just been reaped, we can no
+        * clears p->sighand.  If p has just been reaped, we can no
         * longer get any information about it at all.
         */
-       if (unlikely(p->signal == NULL)) {
+       if (unlikely(p->sighand == NULL)) {
                read_unlock(&tasklist_lock);
                put_task_struct(p);
                timer->it.cpu.task = NULL;
@@ -732,6 +685,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
        BUG_ON(!irqs_disabled());
 
        ret = 0;
+       old_incr = timer->it.cpu.incr;
        spin_lock(&p->sighand->siglock);
        old_expires = timer->it.cpu.expires;
        if (unlikely(timer->it.cpu.firing)) {
@@ -739,7 +693,6 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
                ret = TIMER_RETRY;
        } else
                list_del_init(&timer->it.cpu.entry);
-       spin_unlock(&p->sighand->siglock);
 
        /*
         * We need to sample the current value to convert the new
@@ -752,7 +705,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
                cpu_clock_sample(timer->it_clock, p, &val);
        } else {
-               cpu_clock_sample_group(timer->it_clock, p, &val);
+               cpu_timer_sample_group(timer->it_clock, p, &val);
        }
 
        if (old) {
@@ -793,6 +746,7 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
                 * disable this firing since we are already reporting
                 * it as an overrun (thanks to bump_cpu_timer above).
                 */
+               spin_unlock(&p->sighand->siglock);
                read_unlock(&tasklist_lock);
                goto out;
        }
@@ -808,11 +762,11 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
         */
        timer->it.cpu.expires = new_expires;
        if (new_expires.sched != 0 &&
-           (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
            cpu_time_before(timer->it_clock, val, new_expires)) {
-               arm_timer(timer, val);
+               arm_timer(timer);
        }
 
+       spin_unlock(&p->sighand->siglock);
        read_unlock(&tasklist_lock);
 
        /*
@@ -833,7 +787,6 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
        timer->it_overrun = -1;
 
        if (new_expires.sched != 0 &&
-           (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
            !cpu_time_before(timer->it_clock, val, new_expires)) {
                /*
                 * The designated time already passed, so we notify
@@ -847,12 +800,12 @@ int posix_cpu_timer_set(struct k_itimer *timer, int flags,
  out:
        if (old) {
                sample_to_timespec(timer->it_clock,
-                                  timer->it.cpu.incr, &old->it_interval);
+                                  old_incr, &old->it_interval);
        }
        return ret;
 }
 
-void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
+static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 {
        union cpu_time_count now;
        struct task_struct *p = timer->it.cpu.task;
@@ -888,7 +841,7 @@ void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
                clear_dead = p->exit_state;
        } else {
                read_lock(&tasklist_lock);
-               if (unlikely(p->signal == NULL)) {
+               if (unlikely(p->sighand == NULL)) {
                        /*
                         * The process has been reaped.
                         * We can't even collect a sample any more.
@@ -900,32 +853,13 @@ void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
                        read_unlock(&tasklist_lock);
                        goto dead;
                } else {
-                       cpu_clock_sample_group(timer->it_clock, p, &now);
+                       cpu_timer_sample_group(timer->it_clock, p, &now);
                        clear_dead = (unlikely(p->exit_state) &&
                                      thread_group_empty(p));
                }
                read_unlock(&tasklist_lock);
        }
 
-       if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
-               if (timer->it.cpu.incr.sched == 0 &&
-                   cpu_time_before(timer->it_clock,
-                                   timer->it.cpu.expires, now)) {
-                       /*
-                        * Do-nothing timer expired and has no reload,
-                        * so it's as if it was never set.
-                        */
-                       timer->it.cpu.expires.sched = 0;
-                       itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
-                       return;
-               }
-               /*
-                * Account for any expirations and reloads that should
-                * have happened.
-                */
-               bump_cpu_timer(timer, now);
-       }
-
        if (unlikely(clear_dead)) {
                /*
                 * We've noticed that the thread is dead, but
@@ -961,15 +895,17 @@ static void check_thread_timers(struct task_struct *tsk,
 {
        int maxfire;
        struct list_head *timers = tsk->cpu_timers;
+       struct signal_struct *const sig = tsk->signal;
+       unsigned long soft;
 
        maxfire = 20;
-       tsk->it_prof_expires = cputime_zero;
+       tsk->cputime_expires.prof_exp = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *t = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
-                       tsk->it_prof_expires = t->expires.cpu;
+               if (!--maxfire || prof_ticks(tsk) < t->expires.cpu) {
+                       tsk->cputime_expires.prof_exp = t->expires.cpu;
                        break;
                }
                t->firing = 1;
@@ -978,13 +914,13 @@ static void check_thread_timers(struct task_struct *tsk,
 
        ++timers;
        maxfire = 20;
-       tsk->it_virt_expires = cputime_zero;
+       tsk->cputime_expires.virt_exp = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *t = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
-                       tsk->it_virt_expires = t->expires.cpu;
+               if (!--maxfire || virt_ticks(tsk) < t->expires.cpu) {
+                       tsk->cputime_expires.virt_exp = t->expires.cpu;
                        break;
                }
                t->firing = 1;
@@ -993,18 +929,106 @@ static void check_thread_timers(struct task_struct *tsk,
 
        ++timers;
        maxfire = 20;
-       tsk->it_sched_expires = 0;
+       tsk->cputime_expires.sched_exp = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *t = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || tsk->sched_time < t->expires.sched) {
-                       tsk->it_sched_expires = t->expires.sched;
+               if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
+                       tsk->cputime_expires.sched_exp = t->expires.sched;
                        break;
                }
                t->firing = 1;
                list_move_tail(&t->entry, firing);
        }
+
+       /*
+        * Check for the special case thread timers.
+        */
+       soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
+       if (soft != RLIM_INFINITY) {
+               unsigned long hard =
+                       ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
+
+               if (hard != RLIM_INFINITY &&
+                   tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
+                       /*
+                        * At the hard limit, we just die.
+                        * No need to calculate anything else now.
+                        */
+                       __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
+                       return;
+               }
+               if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
+                       /*
+                        * At the soft limit, send a SIGXCPU every second.
+                        */
+                       if (soft < hard) {
+                               soft += USEC_PER_SEC;
+                               sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
+                       }
+                       printk(KERN_INFO
+                               "RT Watchdog Timeout: %s[%d]\n",
+                               tsk->comm, task_pid_nr(tsk));
+                       __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
+               }
+       }
+}
+
+static void stop_process_timers(struct signal_struct *sig)
+{
+       struct thread_group_cputimer *cputimer = &sig->cputimer;
+       unsigned long flags;
+
+       raw_spin_lock_irqsave(&cputimer->lock, flags);
+       cputimer->running = 0;
+       raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+}
+
+static u32 onecputick;
+
+static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
+                            cputime_t *expires, cputime_t cur_time, int signo)
+{
+       if (!it->expires)
+               return;
+
+       if (cur_time >= it->expires) {
+               if (it->incr) {
+                       it->expires += it->incr;
+                       it->error += it->incr_error;
+                       if (it->error >= onecputick) {
+                               it->expires -= cputime_one_jiffy;
+                               it->error -= onecputick;
+                       }
+               } else {
+                       it->expires = 0;
+               }
+
+               trace_itimer_expire(signo == SIGPROF ?
+                                   ITIMER_PROF : ITIMER_VIRTUAL,
+                                   tsk->signal->leader_pid, cur_time);
+               __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
+       }
+
+       if (it->expires && (!*expires || it->expires < *expires)) {
+               *expires = it->expires;
+       }
+}
+
+/**
+ * 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;
 }
 
 /*
@@ -1017,120 +1041,77 @@ static void check_process_timers(struct task_struct *tsk,
 {
        int maxfire;
        struct signal_struct *const sig = tsk->signal;
-       cputime_t utime, stime, ptime, virt_expires, prof_expires;
-       unsigned long long sched_time, sched_expires;
-       struct task_struct *t;
+       cputime_t utime, ptime, virt_expires, prof_expires;
+       unsigned long long sum_sched_runtime, sched_expires;
        struct list_head *timers = sig->cpu_timers;
-
-       /*
-        * Don't sample the current process CPU clocks if there are no timers.
-        */
-       if (list_empty(&timers[CPUCLOCK_PROF]) &&
-           cputime_eq(sig->it_prof_expires, cputime_zero) &&
-           sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
-           list_empty(&timers[CPUCLOCK_VIRT]) &&
-           cputime_eq(sig->it_virt_expires, cputime_zero) &&
-           list_empty(&timers[CPUCLOCK_SCHED]))
-               return;
+       struct task_cputime cputime;
+       unsigned long soft;
 
        /*
         * Collect the current process totals.
         */
-       utime = sig->utime;
-       stime = sig->stime;
-       sched_time = sig->sched_time;
-       t = tsk;
-       do {
-               utime = cputime_add(utime, t->utime);
-               stime = cputime_add(stime, t->stime);
-               sched_time += t->sched_time;
-               t = next_thread(t);
-       } while (t != tsk);
-       ptime = cputime_add(utime, stime);
-
+       thread_group_cputimer(tsk, &cputime);
+       utime = cputime.utime;
+       ptime = utime + cputime.stime;
+       sum_sched_runtime = cputime.sum_exec_runtime;
        maxfire = 20;
-       prof_expires = cputime_zero;
+       prof_expires = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *tl = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
-                       prof_expires = t->expires.cpu;
+               if (!--maxfire || ptime < tl->expires.cpu) {
+                       prof_expires = tl->expires.cpu;
                        break;
                }
-               t->firing = 1;
-               list_move_tail(&t->entry, firing);
+               tl->firing = 1;
+               list_move_tail(&tl->entry, firing);
        }
 
        ++timers;
        maxfire = 20;
-       virt_expires = cputime_zero;
+       virt_expires = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *tl = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
-                       virt_expires = t->expires.cpu;
+               if (!--maxfire || utime < tl->expires.cpu) {
+                       virt_expires = tl->expires.cpu;
                        break;
                }
-               t->firing = 1;
-               list_move_tail(&t->entry, firing);
+               tl->firing = 1;
+               list_move_tail(&tl->entry, firing);
        }
 
        ++timers;
        maxfire = 20;
        sched_expires = 0;
        while (!list_empty(timers)) {
-               struct cpu_timer_list *t = list_entry(timers->next,
+               struct cpu_timer_list *tl = list_first_entry(timers,
                                                      struct cpu_timer_list,
                                                      entry);
-               if (!--maxfire || sched_time < t->expires.sched) {
-                       sched_expires = t->expires.sched;
+               if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
+                       sched_expires = tl->expires.sched;
                        break;
                }
-               t->firing = 1;
-               list_move_tail(&t->entry, firing);
+               tl->firing = 1;
+               list_move_tail(&tl->entry, firing);
        }
 
        /*
         * Check for the special case process timers.
         */
-       if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-               if (cputime_ge(ptime, sig->it_prof_expires)) {
-                       /* ITIMER_PROF fires and reloads.  */
-                       sig->it_prof_expires = sig->it_prof_incr;
-                       if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
-                               sig->it_prof_expires = cputime_add(
-                                       sig->it_prof_expires, ptime);
-                       }
-                       __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
-               }
-               if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
-                   (cputime_eq(prof_expires, cputime_zero) ||
-                    cputime_lt(sig->it_prof_expires, prof_expires))) {
-                       prof_expires = sig->it_prof_expires;
-               }
-       }
-       if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-               if (cputime_ge(utime, sig->it_virt_expires)) {
-                       /* ITIMER_VIRTUAL fires and reloads.  */
-                       sig->it_virt_expires = sig->it_virt_incr;
-                       if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
-                               sig->it_virt_expires = cputime_add(
-                                       sig->it_virt_expires, utime);
-                       }
-                       __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
-               }
-               if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
-                   (cputime_eq(virt_expires, cputime_zero) ||
-                    cputime_lt(sig->it_virt_expires, virt_expires))) {
-                       virt_expires = sig->it_virt_expires;
-               }
-       }
-       if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
+       check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
+                        SIGPROF);
+       check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
+                        SIGVTALRM);
+       soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+       if (soft != RLIM_INFINITY) {
                unsigned long psecs = cputime_to_secs(ptime);
+               unsigned long hard =
+                       ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
                cputime_t x;
-               if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
+               if (psecs >= hard) {
                        /*
                         * At the hard limit, we just die.
                         * No need to calculate anything else now.
@@ -1138,77 +1119,27 @@ static void check_process_timers(struct task_struct *tsk,
                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
                        return;
                }
-               if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
+               if (psecs >= soft) {
                        /*
                         * At the soft limit, send a SIGXCPU every second.
                         */
                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
-                       if (sig->rlim[RLIMIT_CPU].rlim_cur
-                           < sig->rlim[RLIMIT_CPU].rlim_max) {
-                               sig->rlim[RLIMIT_CPU].rlim_cur++;
+                       if (soft < hard) {
+                               soft++;
+                               sig->rlim[RLIMIT_CPU].rlim_cur = soft;
                        }
                }
-               x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
-               if (cputime_eq(prof_expires, cputime_zero) ||
-                   cputime_lt(x, prof_expires)) {
+               x = secs_to_cputime(soft);
+               if (!prof_expires || x < prof_expires) {
                        prof_expires = x;
                }
        }
 
-       if (!cputime_eq(prof_expires, cputime_zero) ||
-           !cputime_eq(virt_expires, cputime_zero) ||
-           sched_expires != 0) {
-               /*
-                * Rebalance the threads' expiry times for the remaining
-                * process CPU timers.
-                */
-
-               cputime_t prof_left, virt_left, ticks;
-               unsigned long long sched_left, sched;
-               const unsigned int nthreads = atomic_read(&sig->live);
-
-               if (!nthreads)
-                       return;
-
-               prof_left = cputime_sub(prof_expires, utime);
-               prof_left = cputime_sub(prof_left, stime);
-               prof_left = cputime_div(prof_left, nthreads);
-               virt_left = cputime_sub(virt_expires, utime);
-               virt_left = cputime_div(virt_left, nthreads);
-               if (sched_expires) {
-                       sched_left = sched_expires - sched_time;
-                       do_div(sched_left, nthreads);
-               } else {
-                       sched_left = 0;
-               }
-               t = tsk;
-               do {
-                       ticks = cputime_add(cputime_add(t->utime, t->stime),
-                                           prof_left);
-                       if (!cputime_eq(prof_expires, cputime_zero) &&
-                           (cputime_eq(t->it_prof_expires, cputime_zero) ||
-                            cputime_gt(t->it_prof_expires, ticks))) {
-                               t->it_prof_expires = ticks;
-                       }
-
-                       ticks = cputime_add(t->utime, virt_left);
-                       if (!cputime_eq(virt_expires, cputime_zero) &&
-                           (cputime_eq(t->it_virt_expires, cputime_zero) ||
-                            cputime_gt(t->it_virt_expires, ticks))) {
-                               t->it_virt_expires = ticks;
-                       }
-
-                       sched = t->sched_time + sched_left;
-                       if (sched_expires && (t->it_sched_expires == 0 ||
-                                             t->it_sched_expires > sched)) {
-                               t->it_sched_expires = sched;
-                       }
-
-                       do {
-                               t = next_thread(t);
-                       } while (unlikely(t->exit_state));
-               } while (t != tsk);
-       }
+       sig->cputime_expires.prof_exp = prof_expires;
+       sig->cputime_expires.virt_exp = virt_expires;
+       sig->cputime_expires.sched_exp = sched_expires;
+       if (task_cputime_zero(&sig->cputime_expires))
+               stop_process_timers(sig);
 }
 
 /*
@@ -1224,7 +1155,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                /*
                 * The task was cleaned up already, no future firings.
                 */
-               return;
+               goto out;
 
        /*
         * Fetch the current sample and update the timer's expiry time.
@@ -1234,12 +1165,13 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                bump_cpu_timer(timer, now);
                if (unlikely(p->exit_state)) {
                        clear_dead_task(timer, now);
-                       return;
+                       goto out;
                }
                read_lock(&tasklist_lock); /* arm_timer needs it.  */
+               spin_lock(&p->sighand->siglock);
        } else {
                read_lock(&tasklist_lock);
-               if (unlikely(p->signal == NULL)) {
+               if (unlikely(p->sighand == NULL)) {
                        /*
                         * The process has been reaped.
                         * We can't even collect a sample any more.
@@ -1247,8 +1179,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                        put_task_struct(p);
                        timer->it.cpu.task = p = NULL;
                        timer->it.cpu.expires.sched = 0;
-                       read_unlock(&tasklist_lock);
-                       return;
+                       goto out_unlock;
                } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
                        /*
                         * We've noticed that the thread is dead, but
@@ -1256,10 +1187,10 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                         * drop our task ref.
                         */
                        clear_dead_task(timer, now);
-                       read_unlock(&tasklist_lock);
-                       return;
+                       goto out_unlock;
                }
-               cpu_clock_sample_group(timer->it_clock, p, &now);
+               spin_lock(&p->sighand->siglock);
+               cpu_timer_sample_group(timer->it_clock, p, &now);
                bump_cpu_timer(timer, now);
                /* Leave the tasklist_lock locked for the call below.  */
        }
@@ -1267,9 +1198,80 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
        /*
         * Now re-arm for the new expiry time.
         */
-       arm_timer(timer, now);
+       BUG_ON(!irqs_disabled());
+       arm_timer(timer);
+       spin_unlock(&p->sighand->siglock);
 
+out_unlock:
        read_unlock(&tasklist_lock);
+
+out:
+       timer->it_overrun_last = timer->it_overrun;
+       timer->it_overrun = -1;
+       ++timer->it_requeue_pending;
+}
+
+/**
+ * task_cputime_expired - Compare two task_cputime entities.
+ *
+ * @sample:    The task_cputime structure to be checked for expiration.
+ * @expires:   Expiration times, against which @sample will be checked.
+ *
+ * Checks @sample against @expires to see if any field of @sample has expired.
+ * Returns true if any field of the former is greater than the corresponding
+ * field of the latter if the latter field is set.  Otherwise returns false.
+ */
+static inline int task_cputime_expired(const struct task_cputime *sample,
+                                       const struct task_cputime *expires)
+{
+       if (expires->utime && sample->utime >= expires->utime)
+               return 1;
+       if (expires->stime && sample->utime + sample->stime >= expires->stime)
+               return 1;
+       if (expires->sum_exec_runtime != 0 &&
+           sample->sum_exec_runtime >= expires->sum_exec_runtime)
+               return 1;
+       return 0;
+}
+
+/**
+ * fastpath_timer_check - POSIX CPU timers fast path.
+ *
+ * @tsk:       The task (thread) being checked.
+ *
+ * Check the task and thread group timers.  If both are zero (there are no
+ * timers set) return false.  Otherwise snapshot the task and thread group
+ * timers and compare them with the corresponding expiration times.  Return
+ * true if a timer has expired, else return false.
+ */
+static inline int fastpath_timer_check(struct task_struct *tsk)
+{
+       struct signal_struct *sig;
+
+       if (!task_cputime_zero(&tsk->cputime_expires)) {
+               struct task_cputime task_sample = {
+                       .utime = tsk->utime,
+                       .stime = tsk->stime,
+                       .sum_exec_runtime = tsk->se.sum_exec_runtime
+               };
+
+               if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
+                       return 1;
+       }
+
+       sig = tsk->signal;
+       if (sig->cputimer.running) {
+               struct task_cputime group_sample;
+
+               raw_spin_lock(&sig->cputimer.lock);
+               group_sample = sig->cputimer.cputime;
+               raw_spin_unlock(&sig->cputimer.lock);
+
+               if (task_cputime_expired(&group_sample, &sig->cputime_expires))
+                       return 1;
+       }
+
+       return 0;
 }
 
 /*
@@ -1281,147 +1283,121 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 {
        LIST_HEAD(firing);
        struct k_itimer *timer, *next;
+       unsigned long flags;
 
        BUG_ON(!irqs_disabled());
 
-#define UNEXPIRED(clock) \
-               (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
-                cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
-
-       if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
-           (tsk->it_sched_expires == 0 ||
-            tsk->sched_time < tsk->it_sched_expires))
+       /*
+        * 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;
 
-#undef UNEXPIRED
-
+       if (!lock_task_sighand(tsk, &flags))
+               return;
        /*
-        * Double-check with locks held.
+        * 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.
         */
-       read_lock(&tasklist_lock);
-       if (likely(tsk->signal != NULL)) {
-               spin_lock(&tsk->sighand->siglock);
-
-               /*
-                * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
-                * all the timers that are firing, and put them on the firing list.
-                */
-               check_thread_timers(tsk, &firing);
+       check_thread_timers(tsk, &firing);
+       /*
+        * If there are any active process wide timers (POSIX 1.b, itimers,
+        * RLIMIT_CPU) cputimer must be running.
+        */
+       if (tsk->signal->cputimer.running)
                check_process_timers(tsk, &firing);
 
-               /*
-                * We must release these locks before taking any timer's lock.
-                * There is a potential race with timer deletion here, as the
-                * siglock now protects our private firing list.  We have set
-                * the firing flag in each timer, so that a deletion attempt
-                * that gets the timer lock before we do will give it up and
-                * spin until we've taken care of that timer below.
-                */
-               spin_unlock(&tsk->sighand->siglock);
-       }
-       read_unlock(&tasklist_lock);
+       /*
+        * We must release these locks before taking any timer's lock.
+        * There is a potential race with timer deletion here, as the
+        * siglock now protects our private firing list.  We have set
+        * the firing flag in each timer, so that a deletion attempt
+        * that gets the timer lock before we do will give it up and
+        * spin until we've taken care of that timer below.
+        */
+       unlock_task_sighand(tsk, &flags);
 
        /*
         * Now that all the timers on our list have the firing flag,
-        * noone will touch their list entries but us.  We'll take
+        * no one will touch their list entries but us.  We'll take
         * each timer's lock before clearing its firing flag, so no
         * timer call will interfere.
         */
        list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
-               int firing;
+               int cpu_firing;
+
                spin_lock(&timer->it_lock);
                list_del_init(&timer->it.cpu.entry);
-               firing = timer->it.cpu.firing;
+               cpu_firing = timer->it.cpu.firing;
                timer->it.cpu.firing = 0;
                /*
                 * The firing flag is -1 if we collided with a reset
                 * of the timer, which already reported this
                 * almost-firing as an overrun.  So don't generate an event.
                 */
-               if (likely(firing >= 0)) {
+               if (likely(cpu_firing >= 0))
                        cpu_timer_fire(timer);
-               }
                spin_unlock(&timer->it_lock);
        }
 }
 
 /*
- * Set one of the process-wide special case CPU timers.
- * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
- * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
- * absolute; non-null for ITIMER_*, where *newval is relative and we update
- * it to be absolute, *oldval is absolute and we update it to be relative.
+ * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
+ * The tsk->sighand->siglock must be held by the caller.
  */
 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                           cputime_t *newval, cputime_t *oldval)
 {
        union cpu_time_count now;
-       struct list_head *head;
 
        BUG_ON(clock_idx == CPUCLOCK_SCHED);
-       cpu_clock_sample_group_locked(clock_idx, tsk, &now);
+       cpu_timer_sample_group(clock_idx, tsk, &now);
 
        if (oldval) {
-               if (!cputime_eq(*oldval, cputime_zero)) {
-                       if (cputime_le(*oldval, now.cpu)) {
+               /*
+                * We are setting itimer. The *oldval is absolute and we update
+                * it to be relative, *newval argument is relative and we update
+                * it to be absolute.
+                */
+               if (*oldval) {
+                       if (*oldval <= now.cpu) {
                                /* Just about to fire. */
-                               *oldval = jiffies_to_cputime(1);
+                               *oldval = cputime_one_jiffy;
                        } else {
-                               *oldval = cputime_sub(*oldval, now.cpu);
+                               *oldval -= now.cpu;
                        }
                }
 
-               if (cputime_eq(*newval, cputime_zero))
-                       return;
-               *newval = cputime_add(*newval, now.cpu);
-
-               /*
-                * If the RLIMIT_CPU timer will expire before the
-                * ITIMER_PROF timer, we have nothing else to do.
-                */
-               if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
-                   < cputime_to_secs(*newval))
+               if (!*newval)
                        return;
+               *newval += now.cpu;
        }
 
        /*
-        * Check whether there are any process timers already set to fire
-        * before this one.  If so, we don't have anything more to do.
+        * Update expiration cache if we are the earliest timer, or eventually
+        * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
         */
-       head = &tsk->signal->cpu_timers[clock_idx];
-       if (list_empty(head) ||
-           cputime_ge(list_entry(head->next,
-                                 struct cpu_timer_list, entry)->expires.cpu,
-                      *newval)) {
-               /*
-                * Rejigger each thread's expiry time so that one will
-                * notice before we hit the process-cumulative expiry time.
-                */
-               union cpu_time_count expires = { .sched = 0 };
-               expires.cpu = *newval;
-               process_timer_rebalance(tsk, clock_idx, expires, now);
+       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;
        }
 }
 
-static long posix_cpu_clock_nanosleep_restart(struct restart_block *);
-
-int posix_cpu_nsleep(clockid_t which_clock, int flags,
-                    struct timespec *rqtp)
+static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
+                           struct timespec *rqtp, struct itimerspec *it)
 {
-       struct restart_block *restart_block =
-           &current_thread_info()->restart_block;
        struct k_itimer timer;
        int error;
 
        /*
-        * Diagnose required errors first.
-        */
-       if (CPUCLOCK_PERTHREAD(which_clock) &&
-           (CPUCLOCK_PID(which_clock) == 0 ||
-            CPUCLOCK_PID(which_clock) == current->pid))
-               return -EINVAL;
-
-       /*
         * Set up a temporary timer and then wait for it to go off.
         */
        memset(&timer, 0, sizeof timer);
@@ -1431,13 +1407,13 @@ int posix_cpu_nsleep(clockid_t which_clock, int flags,
        error = posix_cpu_timer_create(&timer);
        timer.it_process = current;
        if (!error) {
-               struct timespec __user *rmtp;
                static struct itimerspec zero_it;
-               struct itimerspec it = { .it_value = *rqtp,
-                                        .it_interval = {} };
+
+               memset(it, 0, sizeof *it);
+               it->it_value = *rqtp;
 
                spin_lock_irq(&timer.it_lock);
-               error = posix_cpu_timer_set(&timer, flags, &it, NULL);
+               error = posix_cpu_timer_set(&timer, flags, it, NULL);
                if (error) {
                        spin_unlock_irq(&timer.it_lock);
                        return error;
@@ -1446,8 +1422,10 @@ int posix_cpu_nsleep(clockid_t which_clock, int flags,
                while (!signal_pending(current)) {
                        if (timer.it.cpu.expires.sched == 0) {
                                /*
-                                * Our timer fired and was reset.
+                                * Our timer fired and was reset, below
+                                * deletion can not fail.
                                 */
+                               posix_cpu_timer_del(&timer);
                                spin_unlock_irq(&timer.it_lock);
                                return 0;
                        }
@@ -1465,55 +1443,112 @@ int posix_cpu_nsleep(clockid_t which_clock, int flags,
                 * We were interrupted by a signal.
                 */
                sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
-               posix_cpu_timer_set(&timer, 0, &zero_it, &it);
+               error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
+               if (!error) {
+                       /*
+                        * Timer is now unarmed, deletion can not fail.
+                        */
+                       posix_cpu_timer_del(&timer);
+               }
                spin_unlock_irq(&timer.it_lock);
 
-               if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
+               while (error == TIMER_RETRY) {
+                       /*
+                        * We need to handle case when timer was or is in the
+                        * middle of firing. In other cases we already freed
+                        * resources.
+                        */
+                       spin_lock_irq(&timer.it_lock);
+                       error = posix_cpu_timer_del(&timer);
+                       spin_unlock_irq(&timer.it_lock);
+               }
+
+               if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
                        /*
                         * It actually did fire already.
                         */
                        return 0;
                }
 
+               error = -ERESTART_RESTARTBLOCK;
+       }
+
+       return error;
+}
+
+static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
+
+static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
+                           struct timespec *rqtp, struct timespec __user *rmtp)
+{
+       struct restart_block *restart_block =
+               &current_thread_info()->restart_block;
+       struct itimerspec it;
+       int error;
+
+       /*
+        * Diagnose required errors first.
+        */
+       if (CPUCLOCK_PERTHREAD(which_clock) &&
+           (CPUCLOCK_PID(which_clock) == 0 ||
+            CPUCLOCK_PID(which_clock) == current->pid))
+               return -EINVAL;
+
+       error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
+
+       if (error == -ERESTART_RESTARTBLOCK) {
+
+               if (flags & TIMER_ABSTIME)
+                       return -ERESTARTNOHAND;
                /*
                 * Report back to the user the time still remaining.
                 */
-               rmtp = (struct timespec __user *) restart_block->arg1;
-               if (rmtp != NULL && !(flags & TIMER_ABSTIME) &&
-                   copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
+               if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
                        return -EFAULT;
 
-               restart_block->fn = posix_cpu_clock_nanosleep_restart;
-               /* Caller already set restart_block->arg1 */
-               restart_block->arg0 = which_clock;
-               restart_block->arg2 = rqtp->tv_sec;
-               restart_block->arg3 = rqtp->tv_nsec;
-
-               error = -ERESTART_RESTARTBLOCK;
+               restart_block->fn = posix_cpu_nsleep_restart;
+               restart_block->nanosleep.clockid = which_clock;
+               restart_block->nanosleep.rmtp = rmtp;
+               restart_block->nanosleep.expires = timespec_to_ns(rqtp);
        }
-
        return error;
 }
 
-static long
-posix_cpu_clock_nanosleep_restart(struct restart_block *restart_block)
+static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
 {
-       clockid_t which_clock = restart_block->arg0;
-       struct timespec t = { .tv_sec = restart_block->arg2,
-                             .tv_nsec = restart_block->arg3 };
-       restart_block->fn = do_no_restart_syscall;
-       return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t);
-}
+       clockid_t which_clock = restart_block->nanosleep.clockid;
+       struct timespec t;
+       struct itimerspec it;
+       int error;
+
+       t = ns_to_timespec(restart_block->nanosleep.expires);
+
+       error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
+
+       if (error == -ERESTART_RESTARTBLOCK) {
+               struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
+               /*
+                * Report back to the user the time still remaining.
+                */
+               if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
+                       return -EFAULT;
+
+               restart_block->nanosleep.expires = timespec_to_ns(&t);
+       }
+       return error;
 
+}
 
 #define PROCESS_CLOCK  MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
 #define THREAD_CLOCK   MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
 
-static int process_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
+static int process_cpu_clock_getres(const clockid_t which_clock,
+                                   struct timespec *tp)
 {
        return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
 }
-static int process_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
+static int process_cpu_clock_get(const clockid_t which_clock,
+                                struct timespec *tp)
 {
        return posix_cpu_clock_get(PROCESS_CLOCK, tp);
 }
@@ -1522,16 +1557,23 @@ static int process_cpu_timer_create(struct k_itimer *timer)
        timer->it_clock = PROCESS_CLOCK;
        return posix_cpu_timer_create(timer);
 }
-static int process_cpu_nsleep(clockid_t which_clock, int flags,
-                             struct timespec *rqtp)
+static int process_cpu_nsleep(const clockid_t which_clock, int flags,
+                             struct timespec *rqtp,
+                             struct timespec __user *rmtp)
 {
-       return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
+       return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
+}
+static long process_cpu_nsleep_restart(struct restart_block *restart_block)
+{
+       return -EINVAL;
 }
-static int thread_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
+static int thread_cpu_clock_getres(const clockid_t which_clock,
+                                  struct timespec *tp)
 {
        return posix_cpu_clock_getres(THREAD_CLOCK, tp);
 }
-static int thread_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
+static int thread_cpu_clock_get(const clockid_t which_clock,
+                               struct timespec *tp)
 {
        return posix_cpu_clock_get(THREAD_CLOCK, tp);
 }
@@ -1540,31 +1582,41 @@ static int thread_cpu_timer_create(struct k_itimer *timer)
        timer->it_clock = THREAD_CLOCK;
        return posix_cpu_timer_create(timer);
 }
-static int thread_cpu_nsleep(clockid_t which_clock, int flags,
-                             struct timespec *rqtp)
-{
-       return -EINVAL;
-}
+
+struct k_clock clock_posix_cpu = {
+       .clock_getres   = posix_cpu_clock_getres,
+       .clock_set      = posix_cpu_clock_set,
+       .clock_get      = posix_cpu_clock_get,
+       .timer_create   = posix_cpu_timer_create,
+       .nsleep         = posix_cpu_nsleep,
+       .nsleep_restart = posix_cpu_nsleep_restart,
+       .timer_set      = posix_cpu_timer_set,
+       .timer_del      = posix_cpu_timer_del,
+       .timer_get      = posix_cpu_timer_get,
+};
 
 static __init int init_posix_cpu_timers(void)
 {
        struct k_clock process = {
-               .clock_getres = process_cpu_clock_getres,
-               .clock_get = process_cpu_clock_get,
-               .clock_set = do_posix_clock_nosettime,
-               .timer_create = process_cpu_timer_create,
-               .nsleep = process_cpu_nsleep,
+               .clock_getres   = process_cpu_clock_getres,
+               .clock_get      = process_cpu_clock_get,
+               .timer_create   = process_cpu_timer_create,
+               .nsleep         = process_cpu_nsleep,
+               .nsleep_restart = process_cpu_nsleep_restart,
        };
        struct k_clock thread = {
-               .clock_getres = thread_cpu_clock_getres,
-               .clock_get = thread_cpu_clock_get,
-               .clock_set = do_posix_clock_nosettime,
-               .timer_create = thread_cpu_timer_create,
-               .nsleep = thread_cpu_nsleep,
+               .clock_getres   = thread_cpu_clock_getres,
+               .clock_get      = thread_cpu_clock_get,
+               .timer_create   = thread_cpu_timer_create,
        };
+       struct timespec ts;
+
+       posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
+       posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
 
-       register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
-       register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
+       cputime_to_timespec(cputime_one_jiffy, &ts);
+       onecputick = ts.tv_nsec;
+       WARN_ON(ts.tv_sec != 0);
 
        return 0;
 }