Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  hrtimers: fix warning in kernel/hrtimer.c
  x86: make sure we really have an hpet mapping before using it
  x86: enable HPET on Fujitsu u9200
  linux/timex.h: cleanup for userspace
  posix-timers: simplify de_thread()->exit_itimers() path
  posix-timers: check ->it_signal instead of ->it_pid to validate the timer
  posix-timers: use "struct pid*" instead of "struct task_struct*"
  nohz: suppress needless timer reprogramming
  clocksource, acpi_pm.c: put acpi_pm_read_slow() under CONFIG_PCI
  nohz: no softirq pending warnings for offline cpus
  hrtimer: removing all ur callback modes, fix
  hrtimer: removing all ur callback modes, fix hotplug
  hrtimer: removing all ur callback modes
  x86: correct link to HPET timer specification
  rtc-cmos: export second NVRAM bank

Fixed up conflicts in sound/drivers/pcsp/pcsp.c and sound/core/hrtimer.c
manually.

6 files changed, 107 insertions, 315 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 47e63349d1b..bda9cb92427 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -442,22 +442,6 @@ static inline void debug_hrtimer_activate(struct hrtimer *timer) { }
 static inline void debug_hrtimer_deactivate(struct hrtimer *timer) { }
 #endif
 
-/*
- * Check, whether the timer is on the callback pending list
- */
-static inline int hrtimer_cb_pending(const struct hrtimer *timer)
-{
-        return timer->state & HRTIMER_STATE_PENDING;
-}
-
-/*
- * Remove a timer from the callback pending list
- */
-static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
-{
-        list_del_init(&timer->cb_entry);
-}
-
 /* High resolution timer related functions */
 #ifdef CONFIG_HIGH_RES_TIMERS
 
@@ -651,6 +635,8 @@ static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
 {
 }
 
+static void __run_hrtimer(struct hrtimer *timer);
+
 /*
  * When High resolution timers are active, try to reprogram. Note, that in case
  * the state has HRTIMER_STATE_CALLBACK set, no reprogramming and no expiry
@@ -661,31 +647,14 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
                                             struct hrtimer_clock_base *base)
 {
         if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {
-
-                /* Timer is expired, act upon the callback mode */
-                switch(timer->cb_mode) {
-                case HRTIMER_CB_IRQSAFE_PERCPU:
-                case HRTIMER_CB_IRQSAFE_UNLOCKED:
-                        /*
-                         * This is solely for the sched tick emulation with
-                         * dynamic tick support to ensure that we do not
-                         * restart the tick right on the edge and end up with
-                         * the tick timer in the softirq ! The calling site
-                         * takes care of this. Also used for hrtimer sleeper !
-                         */
-                        debug_hrtimer_deactivate(timer);
-                        return 1;
-                case HRTIMER_CB_SOFTIRQ:
-                        /*
-                         * Move everything else into the softirq pending list !
-                         */
-                        list_add_tail(&timer->cb_entry,
-                                      &base->cpu_base->cb_pending);
-                        timer->state = HRTIMER_STATE_PENDING;
-                        return 1;
-                default:
-                        BUG();
-                }
+                /*
+                 * XXX: recursion check?
+                 * hrtimer_forward() should round up with timer granularity
+                 * so that we never get into inf recursion here,
+                 * it doesn't do that though
+                 */
+                __run_hrtimer(timer);
+                return 1;
         }
         return 0;
 }
@@ -724,11 +693,6 @@ static int hrtimer_switch_to_hres(void)
         return 1;
 }
 
-static inline void hrtimer_raise_softirq(void)
-{
-        raise_softirq(HRTIMER_SOFTIRQ);
-}
-
 #else
 
 static inline int hrtimer_hres_active(void) { return 0; }
@@ -747,7 +711,6 @@ static inline int hrtimer_reprogram(struct hrtimer *timer,
 {
         return 0;
 }
-static inline void hrtimer_raise_softirq(void) { }
 
 #endif /* CONFIG_HIGH_RES_TIMERS */
 
@@ -890,10 +853,7 @@ static void __remove_hrtimer(struct hrtimer *timer,
                              struct hrtimer_clock_base *base,
                              unsigned long newstate, int reprogram)
 {
-        /* High res. callback list. NOP for !HIGHRES */
-        if (hrtimer_cb_pending(timer))
-                hrtimer_remove_cb_pending(timer);
-        else {
+        if (timer->state & HRTIMER_STATE_ENQUEUED) {
                 /*
                  * Remove the timer from the rbtree and replace the
                  * first entry pointer if necessary.
@@ -953,7 +913,7 @@ hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_n
 {
         struct hrtimer_clock_base *base, *new_base;
         unsigned long flags;
-        int ret, raise;
+        int ret;
 
         base = lock_hrtimer_base(timer, &flags);
 
@@ -988,26 +948,8 @@ hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, unsigned long delta_n
         enqueue_hrtimer(timer, new_base,
                         new_base->cpu_base == &__get_cpu_var(hrtimer_bases));
 
-        /*
-         * The timer may be expired and moved to the cb_pending
-         * list. We can not raise the softirq with base lock held due
-         * to a possible deadlock with runqueue lock.
-         */
-        raise = timer->state == HRTIMER_STATE_PENDING;
-
-        /*
-         * We use preempt_disable to prevent this task from migrating after
-         * setting up the softirq and raising it. Otherwise, if me migrate
-         * we will raise the softirq on the wrong CPU.
-         */
-        preempt_disable();
-
         unlock_hrtimer_base(timer, &flags);
 
-        if (raise)
-                hrtimer_raise_softirq();
-        preempt_enable();
-
         return ret;
 }
 EXPORT_SYMBOL_GPL(hrtimer_start_range_ns);
@@ -1192,75 +1134,6 @@ int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
 }
 EXPORT_SYMBOL_GPL(hrtimer_get_res);
 
-static void run_hrtimer_pending(struct hrtimer_cpu_base *cpu_base)
-{
-        spin_lock_irq(&cpu_base->lock);
-
-        while (!list_empty(&cpu_base->cb_pending)) {
-                enum hrtimer_restart (*fn)(struct hrtimer *);
-                struct hrtimer *timer;
-                int restart;
-                int emulate_hardirq_ctx = 0;
-
-                timer = list_entry(cpu_base->cb_pending.next,
-                                   struct hrtimer, cb_entry);
-
-                debug_hrtimer_deactivate(timer);
-                timer_stats_account_hrtimer(timer);
-
-                fn = timer->function;
-                /*
-                 * A timer might have been added to the cb_pending list
-                 * when it was migrated during a cpu-offline operation.
-                 * Emulate hardirq context for such timers.
-                 */
-                if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU ||
-                    timer->cb_mode == HRTIMER_CB_IRQSAFE_UNLOCKED)
-                        emulate_hardirq_ctx = 1;
-
-                __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
-                spin_unlock_irq(&cpu_base->lock);
-
-                if (unlikely(emulate_hardirq_ctx)) {
-                        local_irq_disable();
-                        restart = fn(timer);
-                        local_irq_enable();
-                } else
-                        restart = fn(timer);
-
-                spin_lock_irq(&cpu_base->lock);
-
-                timer->state &= ~HRTIMER_STATE_CALLBACK;
-                if (restart == HRTIMER_RESTART) {
-                        BUG_ON(hrtimer_active(timer));
-                        /*
-                         * Enqueue the timer, allow reprogramming of the event
-                         * device
-                         */
-                        enqueue_hrtimer(timer, timer->base, 1);
-                } else if (hrtimer_active(timer)) {
-                        /*
-                         * If the timer was rearmed on another CPU, reprogram
-                         * the event device.
-                         */
-                        struct hrtimer_clock_base *base = timer->base;
-
-                        if (base->first == &timer->node &&
-                            hrtimer_reprogram(timer, base)) {
-                                /*
-                                 * Timer is expired. Thus move it from tree to
-                                 * pending list again.
-                                 */
-                                __remove_hrtimer(timer, base,
-                                                 HRTIMER_STATE_PENDING, 0);
-                                list_add_tail(&timer->cb_entry,
-                                              &base->cpu_base->cb_pending);
-                        }
-                }
-        }
-        spin_unlock_irq(&cpu_base->lock);
-}
-
 static void __run_hrtimer(struct hrtimer *timer)
 {
         struct hrtimer_clock_base *base = timer->base;
@@ -1268,25 +1141,21 @@ static void __run_hrtimer(struct hrtimer *timer)
         enum hrtimer_restart (*fn)(struct hrtimer *);
         int restart;
 
+        WARN_ON(!irqs_disabled());
+
         debug_hrtimer_deactivate(timer);
         __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
         timer_stats_account_hrtimer(timer);
-
         fn = timer->function;
-        if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU ||
-            timer->cb_mode == HRTIMER_CB_IRQSAFE_UNLOCKED) {
-                /*
-                 * Used for scheduler timers, avoid lock inversion with
-                 * rq->lock and tasklist_lock.
-                 *
-                 * These timers are required to deal with enqueue expiry
-                 * themselves and are not allowed to migrate.
-                 */
-                spin_unlock(&cpu_base->lock);
-                restart = fn(timer);
-                spin_lock(&cpu_base->lock);
-        } else
-                restart = fn(timer);
+
+        /*
+         * Because we run timers from hardirq context, there is no chance
+         * they get migrated to another cpu, therefore its safe to unlock
+         * the timer base.
+         */
+        spin_unlock(&cpu_base->lock);
+        restart = fn(timer);
+        spin_lock(&cpu_base->lock);
 
         /*
          * Note: We clear the CALLBACK bit after enqueue_hrtimer to avoid
@@ -1311,7 +1180,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
         struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
         struct hrtimer_clock_base *base;
         ktime_t expires_next, now;
-        int i, raise = 0;
+        int i;
 
         BUG_ON(!cpu_base->hres_active);
         cpu_base->nr_events++;
@@ -1360,16 +1229,6 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                                 break;
                         }
 
-                        /* Move softirq callbacks to the pending list */
-                        if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
-                                __remove_hrtimer(timer, base,
-                                                 HRTIMER_STATE_PENDING, 0);
-                                list_add_tail(&timer->cb_entry,
-                                              &base->cpu_base->cb_pending);
-                                raise = 1;
-                                continue;
-                        }
-
                         __run_hrtimer(timer);
                 }
                 spin_unlock(&cpu_base->lock);
@@ -1383,10 +1242,6 @@ void hrtimer_interrupt(struct clock_event_device *dev)
                 if (tick_program_event(expires_next, 0))
                         goto retry;
         }
-
-        /* Raise softirq ? */
-        if (raise)
-                raise_softirq(HRTIMER_SOFTIRQ);
 }
 
 /**
@@ -1413,11 +1268,6 @@ void hrtimer_peek_ahead_timers(void)
         local_irq_restore(flags);
 }
 
-static void run_hrtimer_softirq(struct softirq_action *h)
-{
-        run_hrtimer_pending(&__get_cpu_var(hrtimer_bases));
-}
-
 #endif  /* CONFIG_HIGH_RES_TIMERS */
 
 /*
@@ -1429,8 +1279,6 @@ static void run_hrtimer_softirq(struct softirq_action *h)
  */
 void hrtimer_run_pending(void)
 {
-        struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
-
         if (hrtimer_hres_active())
                 return;
 
@@ -1444,8 +1292,6 @@ void hrtimer_run_pending(void)
          */
         if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
                 hrtimer_switch_to_hres();
-
-        run_hrtimer_pending(cpu_base);
 }
 
 /*
@@ -1482,14 +1328,6 @@ void hrtimer_run_queues(void)
                                         hrtimer_get_expires_tv64(timer))
                                 break;
 
-                        if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
-                                __remove_hrtimer(timer, base,
-                                        HRTIMER_STATE_PENDING, 0);
-                                list_add_tail(&timer->cb_entry,
-                                        &base->cpu_base->cb_pending);
-                                continue;
-                        }
-
                         __run_hrtimer(timer);
                 }
                 spin_unlock(&cpu_base->lock);
@@ -1516,9 +1354,6 @@ void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
 {
         sl->timer.function = hrtimer_wakeup;
         sl->task = task;
-#ifdef CONFIG_HIGH_RES_TIMERS
-        sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_UNLOCKED;
-#endif
 }
 
 static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
@@ -1655,18 +1490,16 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
                 cpu_base->clock_base[i].cpu_base = cpu_base;
 
-        INIT_LIST_HEAD(&cpu_base->cb_pending);
         hrtimer_init_hres(cpu_base);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
 
-static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
-                                struct hrtimer_clock_base *new_base, int dcpu)
+static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
+                                struct hrtimer_clock_base *new_base)
 {
         struct hrtimer *timer;
         struct rb_node *node;
-        int raise = 0;
 
         while ((node = rb_first(&old_base->active))) {
                 timer = rb_entry(node, struct hrtimer, node);
@@ -1674,18 +1507,6 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
                 debug_hrtimer_deactivate(timer);
 
                 /*
-                 * Should not happen. Per CPU timers should be
-                 * canceled _before_ the migration code is called
-                 */
-                if (timer->cb_mode == HRTIMER_CB_IRQSAFE_PERCPU) {
-                        __remove_hrtimer(timer, old_base,
-                                         HRTIMER_STATE_INACTIVE, 0);
-                        WARN(1, "hrtimer (%p %p)active but cpu %d dead\n",
-                             timer, timer->function, dcpu);
-                        continue;
-                }
-
-                /*
                  * Mark it as STATE_MIGRATE not INACTIVE otherwise the
                  * timer could be seen as !active and just vanish away
                  * under us on another CPU
@@ -1693,69 +1514,34 @@ static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
                 __remove_hrtimer(timer, old_base, HRTIMER_STATE_MIGRATE, 0);
                 timer->base = new_base;
                 /*
-                 * Enqueue the timer. Allow reprogramming of the event device
+                 * Enqueue the timers on the new cpu, but do not reprogram 
+                 * the timer as that would enable a deadlock between
+                 * hrtimer_enqueue_reprogramm() running the timer and us still
+                 * holding a nested base lock.
+                 *
+                 * Instead we tickle the hrtimer interrupt after the migration
+                 * is done, which will run all expired timers and re-programm
+                 * the timer device.
                  */
-                enqueue_hrtimer(timer, new_base, 1);
+                enqueue_hrtimer(timer, new_base, 0);
 
-#ifdef CONFIG_HIGH_RES_TIMERS
-                /*
-                 * Happens with high res enabled when the timer was
-                 * already expired and the callback mode is
-                 * HRTIMER_CB_IRQSAFE_UNLOCKED (hrtimer_sleeper). The
-                 * enqueue code does not move them to the soft irq
-                 * pending list for performance/latency reasons, but
-                 * in the migration state, we need to do that
-                 * otherwise we end up with a stale timer.
-                 */
-                if (timer->state == HRTIMER_STATE_MIGRATE) {
-                        timer->state = HRTIMER_STATE_PENDING;
-                        list_add_tail(&timer->cb_entry,
-                                      &new_base->cpu_base->cb_pending);
-                        raise = 1;
-                }
-#endif
                 /* Clear the migration state bit */
                 timer->state &= ~HRTIMER_STATE_MIGRATE;
         }
-        return raise;
-}
-
-#ifdef CONFIG_HIGH_RES_TIMERS
-static int migrate_hrtimer_pending(struct hrtimer_cpu_base *old_base,
-                                   struct hrtimer_cpu_base *new_base)
-{
-        struct hrtimer *timer;
-        int raise = 0;
-
-        while (!list_empty(&old_base->cb_pending)) {
-                timer = list_entry(old_base->cb_pending.next,
-                                   struct hrtimer, cb_entry);
-
-                __remove_hrtimer(timer, timer->base, HRTIMER_STATE_PENDING, 0);
-                timer->base = &new_base->clock_base[timer->base->index];
-                list_add_tail(&timer->cb_entry, &new_base->cb_pending);
-                raise = 1;
-        }
-        return raise;
-}
-#else
-static int migrate_hrtimer_pending(struct hrtimer_cpu_base *old_base,
-                                   struct hrtimer_cpu_base *new_base)
-{
-        return 0;
 }
-#endif
 
-static void migrate_hrtimers(int cpu)
+static int migrate_hrtimers(int scpu)
 {
         struct hrtimer_cpu_base *old_base, *new_base;
-        int i, raise = 0;
+        int dcpu, i;
 
-        BUG_ON(cpu_online(cpu));
-        old_base = &per_cpu(hrtimer_bases, cpu);
+        BUG_ON(cpu_online(scpu));
+        old_base = &per_cpu(hrtimer_bases, scpu);
         new_base = &get_cpu_var(hrtimer_bases);
 
-        tick_cancel_sched_timer(cpu);
+        dcpu = smp_processor_id();
+
+        tick_cancel_sched_timer(scpu);
         /*
          * The caller is globally serialized and nobody else
          * takes two locks at once, deadlock is not possible.
@@ -1764,41 +1550,47 @@ static void migrate_hrtimers(int cpu)
         spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
-                if (migrate_hrtimer_list(&old_base->clock_base[i],
-                                         &new_base->clock_base[i], cpu))
-                        raise = 1;
+                migrate_hrtimer_list(&old_base->clock_base[i],
+                                     &new_base->clock_base[i]);
         }
 
-        if (migrate_hrtimer_pending(old_base, new_base))
-                raise = 1;
-
         spin_unlock(&old_base->lock);
         spin_unlock_irq(&new_base->lock);
         put_cpu_var(hrtimer_bases);
 
-        if (raise)
-                hrtimer_raise_softirq();
+        return dcpu;
+}
+
+static void tickle_timers(void *arg)
+{
+        hrtimer_peek_ahead_timers();
 }
+
 #endif /* CONFIG_HOTPLUG_CPU */
 
 static int __cpuinit hrtimer_cpu_notify(struct notifier_block *self,
                                         unsigned long action, void *hcpu)
 {
-        unsigned int cpu = (long)hcpu;
+        int scpu = (long)hcpu;
 
         switch (action) {
 
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
-                init_hrtimers_cpu(cpu);
+                init_hrtimers_cpu(scpu);
                 break;
 
 #ifdef CONFIG_HOTPLUG_CPU
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
-                clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &cpu);
-                migrate_hrtimers(cpu);
+        {
+                int dcpu;
+
+                clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &scpu);
+                dcpu = migrate_hrtimers(scpu);
+                smp_call_function_single(dcpu, tickle_timers, NULL, 0);
                 break;
+        }
 #endif
 
         default:
@@ -1817,9 +1609,6 @@ void __init hrtimers_init(void)
         hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
                           (void *)(long)smp_processor_id());
         register_cpu_notifier(&hrtimers_nb);
-#ifdef CONFIG_HIGH_RES_TIMERS
-        open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq);
-#endif
 }
 
 /**
diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index a140e44eebb..887c63787de 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -116,7 +116,7 @@ static DEFINE_SPINLOCK(idr_lock);
  *          must supply functions here, even if the function just returns
  *          ENOSYS.  The standard POSIX timer management code assumes the
  *          following: 1.) The k_itimer struct (sched.h) is used for the
- *          timer.  2.) The list, it_lock, it_clock, it_id and it_process
+ *          timer.  2.) The list, it_lock, it_clock, it_id and it_pid
  *          fields are not modified by timer code.
  *
  *          At this time all functions EXCEPT clock_nanosleep can be
@@ -319,7 +319,8 @@ void do_schedule_next_timer(struct siginfo *info)
 
 int posix_timer_event(struct k_itimer *timr, int si_private)
 {
-        int shared, ret;
+        struct task_struct *task;
+        int shared, ret = -1;
         /*
          * FIXME: if ->sigq is queued we can race with
          * dequeue_signal()->do_schedule_next_timer().
@@ -333,8 +334,13 @@ int posix_timer_event(struct k_itimer *timr, int si_private)
          */
         timr->sigq->info.si_sys_private = si_private;
 
-        shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
-        ret = send_sigqueue(timr->sigq, timr->it_process, shared);
+        rcu_read_lock();
+        task = pid_task(timr->it_pid, PIDTYPE_PID);
+        if (task) {
+                shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
+                ret = send_sigqueue(timr->sigq, task, shared);
+        }
+        rcu_read_unlock();
         /* If we failed to send the signal the timer stops. */
         return ret > 0;
 }
@@ -411,7 +417,7 @@ static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
         return ret;
 }
 
-static struct task_struct * good_sigevent(sigevent_t * event)
+static struct pid *good_sigevent(sigevent_t * event)
 {
         struct task_struct *rtn = current->group_leader;
 
@@ -425,7 +431,7 @@ static struct task_struct * good_sigevent(sigevent_t * event)
             ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
                 return NULL;
 
-        return rtn;
+        return task_pid(rtn);
 }
 
 void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
@@ -464,6 +470,7 @@ static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
                 idr_remove(&posix_timers_id, tmr->it_id);
                 spin_unlock_irqrestore(&idr_lock, flags);
         }
+        put_pid(tmr->it_pid);
         sigqueue_free(tmr->sigq);
         kmem_cache_free(posix_timers_cache, tmr);
 }
@@ -477,7 +484,6 @@ sys_timer_create(const clockid_t which_clock,
 {
         struct k_itimer *new_timer;
         int error, new_timer_id;
-        struct task_struct *process;
         sigevent_t event;
         int it_id_set = IT_ID_NOT_SET;
 
@@ -531,11 +537,9 @@ sys_timer_create(const clockid_t which_clock,
                         goto out;
                 }
                 rcu_read_lock();
-                process = good_sigevent(&event);
-                if (process)
-                        get_task_struct(process);
+                new_timer->it_pid = get_pid(good_sigevent(&event));
                 rcu_read_unlock();
-                if (!process) {
+                if (!new_timer->it_pid) {
                         error = -EINVAL;
                         goto out;
                 }
@@ -543,8 +547,7 @@ sys_timer_create(const clockid_t which_clock,
                 event.sigev_notify = SIGEV_SIGNAL;
                 event.sigev_signo = SIGALRM;
                 event.sigev_value.sival_int = new_timer->it_id;
-                process = current->group_leader;
-                get_task_struct(process);
+                new_timer->it_pid = get_pid(task_tgid(current));
         }
 
         new_timer->it_sigev_notify     = event.sigev_notify;
@@ -554,7 +557,7 @@ sys_timer_create(const clockid_t which_clock,
         new_timer->sigq->info.si_code  = SI_TIMER;
 
         spin_lock_irq(&current->sighand->siglock);
-        new_timer->it_process = process;
+        new_timer->it_signal = current->signal;
         list_add(&new_timer->list, &current->signal->posix_timers);
         spin_unlock_irq(&current->sighand->siglock);
 
@@ -589,8 +592,7 @@ static struct k_itimer *lock_timer(timer_t timer_id, unsigned long *flags)
         timr = idr_find(&posix_timers_id, (int)timer_id);
         if (timr) {
                 spin_lock(&timr->it_lock);
-                if (timr->it_process &&
-                    same_thread_group(timr->it_process, current)) {
+                if (timr->it_signal == current->signal) {
                         spin_unlock(&idr_lock);
                         return timr;
                 }
@@ -837,8 +839,7 @@ retry_delete:
          * This keeps any tasks waiting on the spin lock from thinking
          * they got something (see the lock code above).
          */
-        put_task_struct(timer->it_process);
-        timer->it_process = NULL;
+        timer->it_signal = NULL;
 
         unlock_timer(timer, flags);
         release_posix_timer(timer, IT_ID_SET);
@@ -864,8 +865,7 @@ retry_delete:
          * This keeps any tasks waiting on the spin lock from thinking
          * they got something (see the lock code above).
          */
-        put_task_struct(timer->it_process);
-        timer->it_process = NULL;
+        timer->it_signal = NULL;
 
         unlock_timer(timer, flags);
         release_posix_timer(timer, IT_ID_SET);
diff --git a/kernel/sched.c b/kernel/sched.c
index 22aa9cab3fe..fff1c4a20b6 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -209,7 +209,6 @@ void init_rt_bandwidth(struct rt_bandwidth *rt_b, u64 period, u64 runtime)
         hrtimer_init(&rt_b->rt_period_timer,
                         CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         rt_b->rt_period_timer.function = sched_rt_period_timer;
-        rt_b->rt_period_timer.cb_mode = HRTIMER_CB_IRQSAFE_UNLOCKED;
 }
 
 static inline int rt_bandwidth_enabled(void)
@@ -1139,7 +1138,6 @@ static void init_rq_hrtick(struct rq *rq)
 
         hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         rq->hrtick_timer.function = hrtick;
-        rq->hrtick_timer.cb_mode = HRTIMER_CB_IRQSAFE_PERCPU;
 }
 #else   /* CONFIG_SCHED_HRTICK */
 static inline void hrtick_clear(struct rq *rq)
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 8ff15e5d486..f5f793d9241 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -131,7 +131,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 {
         enum hrtimer_restart res = HRTIMER_NORESTART;
 
-        write_seqlock_irq(&xtime_lock);
+        write_seqlock(&xtime_lock);
 
         switch (time_state) {
         case TIME_OK:
@@ -164,7 +164,7 @@ static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
         }
         update_vsyscall(&xtime, clock);
 
-        write_sequnlock_irq(&xtime_lock);
+        write_sequnlock(&xtime_lock);
 
         return res;
 }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 342fc9ccab4..8f3fc2582d3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -247,7 +247,7 @@ void tick_nohz_stop_sched_tick(int inidle)
         if (need_resched())
                 goto end;
 
-        if (unlikely(local_softirq_pending())) {
+        if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
                 static int ratelimit;
 
                 if (ratelimit < 10) {
@@ -282,8 +282,31 @@ void tick_nohz_stop_sched_tick(int inidle)
         /* Schedule the tick, if we are at least one jiffie off */
         if ((long)delta_jiffies >= 1) {
 
+                /*
+                * calculate the expiry time for the next timer wheel
+                * timer
+                */
+                expires = ktime_add_ns(last_update, tick_period.tv64 *
+                                   delta_jiffies);
+
+                /*
+                 * If this cpu is the one which updates jiffies, then
+                 * give up the assignment and let it be taken by the
+                 * cpu which runs the tick timer next, which might be
+                 * this cpu as well. If we don't drop this here the
+                 * jiffies might be stale and do_timer() never
+                 * invoked.
+                 */
+                if (cpu == tick_do_timer_cpu)
+                        tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+
                 if (delta_jiffies > 1)
                         cpu_set(cpu, nohz_cpu_mask);
+
+                /* Skip reprogram of event if its not changed */
+                if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
+                        goto out;
+
                 /*
                  * nohz_stop_sched_tick can be called several times before
                  * the nohz_restart_sched_tick is called. This happens when
@@ -306,17 +329,6 @@ void tick_nohz_stop_sched_tick(int inidle)
                         rcu_enter_nohz();
                 }
 
-                /*
-                 * If this cpu is the one which updates jiffies, then
-                 * give up the assignment and let it be taken by the
-                 * cpu which runs the tick timer next, which might be
-                 * this cpu as well. If we don't drop this here the
-                 * jiffies might be stale and do_timer() never
-                 * invoked.
-                 */
-                if (cpu == tick_do_timer_cpu)
-                        tick_do_timer_cpu = TICK_DO_TIMER_NONE;
-
                 ts->idle_sleeps++;
 
                 /*
@@ -332,12 +344,7 @@ void tick_nohz_stop_sched_tick(int inidle)
                         goto out;
                 }
 
-                /*
-                 * calculate the expiry time for the next timer wheel
-                 * timer
-                 */
-                expires = ktime_add_ns(last_update, tick_period.tv64 *
-                                       delta_jiffies);
+                /* Mark expiries */
                 ts->idle_expires = expires;
 
                 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
@@ -681,7 +688,6 @@ void tick_setup_sched_timer(void)
          */
         hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
         ts->sched_timer.function = tick_sched_timer;
-        ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_PERCPU;
 
         /* Get the next period (per cpu) */
         hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
diff --git a/kernel/trace/trace_sysprof.c b/kernel/trace/trace_sysprof.c
index 01becf1f19f..a5779bd975d 100644
--- a/kernel/trace/trace_sysprof.c
+++ b/kernel/trace/trace_sysprof.c
@@ -202,7 +202,6 @@ static void start_stack_timer(int cpu)
 
         hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
         hrtimer->function = stack_trace_timer_fn;
-        hrtimer->cb_mode = HRTIMER_CB_IRQSAFE_PERCPU;
 
         hrtimer_start(hrtimer, ns_to_ktime(sample_period), HRTIMER_MODE_REL);
 }