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

* 'timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  clocksource: Add clocksource_register_hz/khz interface
  posix-cpu-timers: Optimize run_posix_cpu_timers()
  time: Remove xtime_cache
  mqueue: Convert message queue timeout to use hrtimers
  hrtimers: Provide schedule_hrtimeout for CLOCK_REALTIME
  timers: Introduce the concept of timer slack for legacy timers
  ntp: Remove tickadj
  ntp: Make time_adjust static
  time: Add xtime, wall_to_monotonic to feature-removal-schedule
  timer: Try to survive timer callback preempt_count leak
  timer: Split out timer function call
  timer: Print function name for timer callbacks modifying preemption count
  time: Clean up warp_clock()
  cpu-timers: Avoid iterating over all threads in fastpath_timer_check()
  cpu-timers: Change SIGEV_NONE timer implementation
  cpu-timers: Return correct previous timer reload value
  cpu-timers: Cleanup arm_timer()
  cpu-timers: Simplify RLIMIT_CPU handling

7 files changed, 312 insertions, 286 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 0086628b6e97..b9b134b35088 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1749,35 +1749,15 @@ void __init hrtimers_init(void)
 }
 
 /**
- * schedule_hrtimeout_range - sleep until timeout
+ * schedule_hrtimeout_range_clock - sleep until timeout
  * @expires:    timeout value (ktime_t)
  * @delta:      slack in expires timeout (ktime_t)
  * @mode:       timer mode, HRTIMER_MODE_ABS or HRTIMER_MODE_REL
- *
- * Make the current task sleep until the given expiry time has
- * elapsed. The routine will return immediately unless
- * the current task state has been set (see set_current_state()).
- *
- * The @delta argument gives the kernel the freedom to schedule the
- * actual wakeup to a time that is both power and performance friendly.
- * The kernel give the normal best effort behavior for "@expires+@delta",
- * but may decide to fire the timer earlier, but no earlier than @expires.
- *
- * You can set the task state as follows -
- *
- * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
- * pass before the routine returns.
- *
- * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
- * delivered to the current task.
- *
- * The current task state is guaranteed to be TASK_RUNNING when this
- * routine returns.
- *
- * Returns 0 when the timer has expired otherwise -EINTR
+ * @clock:      timer clock, CLOCK_MONOTONIC or CLOCK_REALTIME
  */
-int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
-                               const enum hrtimer_mode mode)
+int __sched
+schedule_hrtimeout_range_clock(ktime_t *expires, unsigned long delta,
+                               const enum hrtimer_mode mode, int clock)
 {
         struct hrtimer_sleeper t;
 
@@ -1799,7 +1779,7 @@ int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
                 return -EINTR;
         }
 
-        hrtimer_init_on_stack(&t.timer, CLOCK_MONOTONIC, mode);
+        hrtimer_init_on_stack(&t.timer, clock, mode);
         hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
 
         hrtimer_init_sleeper(&t, current);
@@ -1818,6 +1798,41 @@ int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
 
         return !t.task ? 0 : -EINTR;
 }
+
+/**
+ * schedule_hrtimeout_range - sleep until timeout
+ * @expires:    timeout value (ktime_t)
+ * @delta:      slack in expires timeout (ktime_t)
+ * @mode:       timer mode, HRTIMER_MODE_ABS or HRTIMER_MODE_REL
+ *
+ * Make the current task sleep until the given expiry time has
+ * elapsed. The routine will return immediately unless
+ * the current task state has been set (see set_current_state()).
+ *
+ * The @delta argument gives the kernel the freedom to schedule the
+ * actual wakeup to a time that is both power and performance friendly.
+ * The kernel give the normal best effort behavior for "@expires+@delta",
+ * but may decide to fire the timer earlier, but no earlier than @expires.
+ *
+ * You can set the task state as follows -
+ *
+ * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
+ * pass before the routine returns.
+ *
+ * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
+ * delivered to the current task.
+ *
+ * The current task state is guaranteed to be TASK_RUNNING when this
+ * routine returns.
+ *
+ * Returns 0 when the timer has expired otherwise -EINTR
+ */
+int __sched schedule_hrtimeout_range(ktime_t *expires, unsigned long delta,
+                                     const enum hrtimer_mode mode)
+{
+        return schedule_hrtimeout_range_clock(expires, delta, mode,
+                                              CLOCK_MONOTONIC);
+}
 EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
 
 /**
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index bc7704b3a443..00bb252f29a2 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -11,19 +11,18 @@
 #include <trace/events/timer.h>
 
 /*
- * Called after updating RLIMIT_CPU to set timer expiration if necessary.
+ * 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(unsigned long rlim_new)
 {
         cputime_t cputime = secs_to_cputime(rlim_new);
-        struct signal_struct *const sig = current->signal;
 
-        if (cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) ||
-            cputime_gt(sig->it[CPUCLOCK_PROF].expires, cputime)) {
-                spin_lock_irq(&current->sighand->siglock);
-                set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
-                spin_unlock_irq(&current->sighand->siglock);
-        }
+        spin_lock_irq(&current->sighand->siglock);
+        set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
+        spin_unlock_irq(&current->sighand->siglock);
 }
 
 static int check_clock(const clockid_t which_clock)
@@ -548,111 +547,62 @@ static inline int expires_gt(cputime_t expires, cputime_t new_exp)
                cputime_gt(expires, new_exp);
 }
 
-static inline int expires_le(cputime_t expires, cputime_t new_exp)
-{
-        return !cputime_eq(expires, cputime_zero) &&
-               cputime_le(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)
-                                break;
-                        listpos = &next->entry;
-                }
-        } else {
-                list_for_each_entry(next, head, entry) {
-                        if (cputime_gt(next->expires.cpu, nt->expires.cpu))
-                                break;
-                        listpos = &next->entry;
-                }
+        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)) {
-                        union cpu_time_count *exp = &nt->expires;
-
-                        switch (CPUCLOCK_WHICH(timer->it_clock)) {
-                        default:
-                                BUG();
-                        case CPUCLOCK_PROF:
-                                if (expires_gt(p->cputime_expires.prof_exp,
-                                               exp->cpu))
-                                        p->cputime_expires.prof_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_VIRT:
-                                if (expires_gt(p->cputime_expires.virt_exp,
-                                               exp->cpu))
-                                        p->cputime_expires.virt_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_SCHED:
-                                if (p->cputime_expires.sched_exp == 0 ||
-                                    p->cputime_expires.sched_exp > exp->sched)
-                                        p->cputime_expires.sched_exp =
-                                                                exp->sched;
-                                break;
-                        }
-                } else {
-                        struct signal_struct *const sig = p->signal;
-                        union cpu_time_count *exp = &timer->it.cpu.expires;
-
-                        /*
-                         * For a process timer, set the cached expiration time.
-                         */
-                        switch (CPUCLOCK_WHICH(timer->it_clock)) {
-                        default:
-                                BUG();
-                        case CPUCLOCK_VIRT:
-                                if (expires_le(sig->it[CPUCLOCK_VIRT].expires,
-                                               exp->cpu))
-                                        break;
-                                sig->cputime_expires.virt_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_PROF:
-                                if (expires_le(sig->it[CPUCLOCK_PROF].expires,
-                                               exp->cpu))
-                                        break;
-                                i = sig->rlim[RLIMIT_CPU].rlim_cur;
-                                if (i != RLIM_INFINITY &&
-                                    i <= cputime_to_secs(exp->cpu))
-                                        break;
-                                sig->cputime_expires.prof_exp = exp->cpu;
-                                break;
-                        case CPUCLOCK_SCHED:
-                                sig->cputime_expires.sched_exp = exp->sched;
-                                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);
 }
 
 /*
@@ -660,7 +610,12 @@ 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.
@@ -721,7 +676,7 @@ 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)) {
@@ -752,6 +707,7 @@ 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)) {
@@ -759,7 +715,6 @@ 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
@@ -813,6 +768,7 @@ 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;
         }
@@ -828,11 +784,11 @@ 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);
 
         /*
@@ -853,7 +809,6 @@ 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
@@ -867,7 +822,7 @@ 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;
 }
@@ -927,25 +882,6 @@ void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
                 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
@@ -1066,16 +1002,9 @@ static void stop_process_timers(struct signal_struct *sig)
         struct thread_group_cputimer *cputimer = &sig->cputimer;
         unsigned long flags;
 
-        if (!cputimer->running)
-                return;
-
         spin_lock_irqsave(&cputimer->lock, flags);
         cputimer->running = 0;
         spin_unlock_irqrestore(&cputimer->lock, flags);
-
-        sig->cputime_expires.prof_exp = cputime_zero;
-        sig->cputime_expires.virt_exp = cputime_zero;
-        sig->cputime_expires.sched_exp = 0;
 }
 
 static u32 onecputick;
@@ -1112,6 +1041,23 @@ static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
         }
 }
 
+/**
+ * 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_eq(cputime->utime, cputime_zero) &&
+            cputime_eq(cputime->stime, cputime_zero) &&
+            cputime->sum_exec_runtime == 0)
+                return 1;
+        return 0;
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them
  * off the tsk->*_timers list onto the firing list.  Per-thread timers
@@ -1129,19 +1075,6 @@ static void check_process_timers(struct task_struct *tsk,
         unsigned long soft;
 
         /*
-         * Don't sample the current process CPU clocks if there are no timers.
-         */
-        if (list_empty(&timers[CPUCLOCK_PROF]) &&
-            cputime_eq(sig->it[CPUCLOCK_PROF].expires, cputime_zero) &&
-            sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
-            list_empty(&timers[CPUCLOCK_VIRT]) &&
-            cputime_eq(sig->it[CPUCLOCK_VIRT].expires, cputime_zero) &&
-            list_empty(&timers[CPUCLOCK_SCHED])) {
-                stop_process_timers(sig);
-                return;
-        }
-
-        /*
          * Collect the current process totals.
          */
         thread_group_cputimer(tsk, &cputime);
@@ -1230,18 +1163,11 @@ static void check_process_timers(struct task_struct *tsk,
                 }
         }
 
-        if (!cputime_eq(prof_expires, cputime_zero) &&
-            (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
-             cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
-                sig->cputime_expires.prof_exp = prof_expires;
-        if (!cputime_eq(virt_expires, cputime_zero) &&
-            (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
-             cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
-                sig->cputime_expires.virt_exp = virt_expires;
-        if (sched_expires != 0 &&
-            (sig->cputime_expires.sched_exp == 0 ||
-             sig->cputime_expires.sched_exp > sched_expires))
-                sig->cputime_expires.sched_exp = sched_expires;
+        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);
 }
 
 /*
@@ -1270,6 +1196,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                         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)) {
@@ -1290,6 +1217,7 @@ void posix_cpu_timer_schedule(struct k_itimer *timer)
                         clear_dead_task(timer, now);
                         goto out_unlock;
                 }
+                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.  */
@@ -1298,7 +1226,9 @@ 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);
@@ -1310,23 +1240,6 @@ out:
 }
 
 /**
- * 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_eq(cputime->utime, cputime_zero) &&
-            cputime_eq(cputime->stime, cputime_zero) &&
-            cputime->sum_exec_runtime == 0)
-                return 1;
-        return 0;
-}
-
-/**
  * task_cputime_expired - Compare two task_cputime entities.
  *
  * @sample:     The task_cputime structure to be checked for expiration.
@@ -1382,7 +1295,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
         }
 
         sig = tsk->signal;
-        if (!task_cputime_zero(&sig->cputime_expires)) {
+        if (sig->cputimer.running) {
                 struct task_cputime group_sample;
 
                 thread_group_cputimer(tsk, &group_sample);
@@ -1390,7 +1303,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
                         return 1;
         }
 
-        return sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY;
+        return 0;
 }
 
 /*
@@ -1419,7 +1332,12 @@ void run_posix_cpu_timers(struct task_struct *tsk)
          * put them on the firing list.
          */
         check_thread_timers(tsk, &firing);
-        check_process_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.
@@ -1456,21 +1374,23 @@ void run_posix_cpu_timers(struct task_struct *tsk)
 }
 
 /*
- * Set one of the process-wide special case CPU timers.
+ * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
  * The tsk->sighand->siglock must be held by the caller.
- * The *newval argument is relative and we update it to be absolute, *oldval
- * is absolute and we update it to be relative.
  */
 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_timer_sample_group(clock_idx, tsk, &now);
 
         if (oldval) {
+                /*
+                 * 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 (!cputime_eq(*oldval, cputime_zero)) {
                         if (cputime_le(*oldval, now.cpu)) {
                                 /* Just about to fire. */
@@ -1483,33 +1403,21 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                 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))
-                        return;
         }
 
         /*
-         * 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_first_entry(head,
-                                  struct cpu_timer_list, entry)->expires.cpu,
-                       *newval)) {
-                switch (clock_idx) {
-                case CPUCLOCK_PROF:
+        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:
+                break;
+        case CPUCLOCK_VIRT:
+                if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
                         tsk->signal->cputime_expires.virt_exp = *newval;
-                        break;
-                }
+                break;
         }
 }
 
diff --git a/kernel/time.c b/kernel/time.c
index 656dccfe1cbb..50612faa9baf 100644
--- a/kernel/time.c
+++ b/kernel/time.c
@@ -132,12 +132,11 @@ SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv,
  */
 static inline void warp_clock(void)
 {
-        write_seqlock_irq(&xtime_lock);
-        wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60;
-        xtime.tv_sec += sys_tz.tz_minuteswest * 60;
-        update_xtime_cache(0);
-        write_sequnlock_irq(&xtime_lock);
-        clock_was_set();
+        struct timespec delta, adjust;
+        delta.tv_sec = sys_tz.tz_minuteswest * 60;
+        delta.tv_nsec = 0;
+        adjust = timespec_add_safe(current_kernel_time(), delta);
+        do_settimeofday(&adjust);
 }
 
 /*
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c
index 1f5dde637457..f08e99c1d561 100644
--- a/kernel/time/clocksource.c
+++ b/kernel/time/clocksource.c
@@ -625,6 +625,54 @@ static void clocksource_enqueue(struct clocksource *cs)
         list_add(&cs->list, entry);
 }
 
+
+/*
+ * Maximum time we expect to go between ticks. This includes idle
+ * tickless time. It provides the trade off between selecting a
+ * mult/shift pair that is very precise but can only handle a short
+ * period of time, vs. a mult/shift pair that can handle long periods
+ * of time but isn't as precise.
+ *
+ * This is a subsystem constant, and actual hardware limitations
+ * may override it (ie: clocksources that wrap every 3 seconds).
+ */
+#define MAX_UPDATE_LENGTH 5 /* Seconds */
+
+/**
+ * __clocksource_register_scale - Used to install new clocksources
+ * @t:          clocksource to be registered
+ * @scale:      Scale factor multiplied against freq to get clocksource hz
+ * @freq:       clocksource frequency (cycles per second) divided by scale
+ *
+ * Returns -EBUSY if registration fails, zero otherwise.
+ *
+ * This *SHOULD NOT* be called directly! Please use the
+ * clocksource_register_hz() or clocksource_register_khz helper functions.
+ */
+int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
+{
+
+        /*
+         * Ideally we want to use  some of the limits used in
+         * clocksource_max_deferment, to provide a more informed
+         * MAX_UPDATE_LENGTH. But for now this just gets the
+         * register interface working properly.
+         */
+        clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
+                                      NSEC_PER_SEC/scale,
+                                      MAX_UPDATE_LENGTH*scale);
+        cs->max_idle_ns = clocksource_max_deferment(cs);
+
+        mutex_lock(&clocksource_mutex);
+        clocksource_enqueue(cs);
+        clocksource_select();
+        clocksource_enqueue_watchdog(cs);
+        mutex_unlock(&clocksource_mutex);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(__clocksource_register_scale);
+
+
 /**
  * clocksource_register - Used to install new clocksources
  * @t:          clocksource to be registered
diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 7c0f180d6e9d..c63116863a80 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -69,7 +69,7 @@ static s64			time_freq;
 /* time at last adjustment (secs):                                      */
 static long                     time_reftime;
 
-long                            time_adjust;
+static long                     time_adjust;
 
 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
 static s64                      ntp_tick_adj;
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 39f6177fafac..caf8d4d4f5c8 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -165,13 +165,6 @@ struct timespec raw_time;
 /* flag for if timekeeping is suspended */
 int __read_mostly timekeeping_suspended;
 
-static struct timespec xtime_cache __attribute__ ((aligned (16)));
-void update_xtime_cache(u64 nsec)
-{
-        xtime_cache = xtime;
-        timespec_add_ns(&xtime_cache, nsec);
-}
-
 /* must hold xtime_lock */
 void timekeeping_leap_insert(int leapsecond)
 {
@@ -332,8 +325,6 @@ int do_settimeofday(struct timespec *tv)
 
         xtime = *tv;
 
-        update_xtime_cache(0);
-
         timekeeper.ntp_error = 0;
         ntp_clear();
 
@@ -559,7 +550,6 @@ void __init timekeeping_init(void)
         }
         set_normalized_timespec(&wall_to_monotonic,
                                 -boot.tv_sec, -boot.tv_nsec);
-        update_xtime_cache(0);
         total_sleep_time.tv_sec = 0;
         total_sleep_time.tv_nsec = 0;
         write_sequnlock_irqrestore(&xtime_lock, flags);
@@ -593,7 +583,6 @@ static int timekeeping_resume(struct sys_device *dev)
                 wall_to_monotonic = timespec_sub(wall_to_monotonic, ts);
                 total_sleep_time = timespec_add_safe(total_sleep_time, ts);
         }
-        update_xtime_cache(0);
         /* re-base the last cycle value */
         timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
         timekeeper.ntp_error = 0;
@@ -788,7 +777,6 @@ void update_wall_time(void)
 {
         struct clocksource *clock;
         cycle_t offset;
-        u64 nsecs;
         int shift = 0, maxshift;
 
         /* Make sure we're fully resumed: */
@@ -847,7 +835,9 @@ void update_wall_time(void)
                 timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
         }
 
-        /* store full nanoseconds into xtime after rounding it up and
+
+        /*
+         * Store full nanoseconds into xtime after rounding it up and
          * add the remainder to the error difference.
          */
         xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1;
@@ -855,8 +845,15 @@ void update_wall_time(void)
         timekeeper.ntp_error += timekeeper.xtime_nsec <<
                                 timekeeper.ntp_error_shift;
 
-        nsecs = clocksource_cyc2ns(offset, timekeeper.mult, timekeeper.shift);
-        update_xtime_cache(nsecs);
+        /*
+         * Finally, make sure that after the rounding
+         * xtime.tv_nsec isn't larger then NSEC_PER_SEC
+         */
+        if (unlikely(xtime.tv_nsec >= NSEC_PER_SEC)) {
+                xtime.tv_nsec -= NSEC_PER_SEC;
+                xtime.tv_sec++;
+                second_overflow();
+        }
 
         /* check to see if there is a new clocksource to use */
         update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult);
@@ -896,13 +893,13 @@ EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
 
 unsigned long get_seconds(void)
 {
-        return xtime_cache.tv_sec;
+        return xtime.tv_sec;
 }
 EXPORT_SYMBOL(get_seconds);
 
 struct timespec __current_kernel_time(void)
 {
-        return xtime_cache;
+        return xtime;
 }
 
 struct timespec current_kernel_time(void)
@@ -913,7 +910,7 @@ struct timespec current_kernel_time(void)
         do {
                 seq = read_seqbegin(&xtime_lock);
 
-                now = xtime_cache;
+                now = xtime;
         } while (read_seqretry(&xtime_lock, seq));
 
         return now;
@@ -928,7 +925,7 @@ struct timespec get_monotonic_coarse(void)
         do {
                 seq = read_seqbegin(&xtime_lock);
 
-                now = xtime_cache;
+                now = xtime;
                 mono = wall_to_monotonic;
         } while (read_seqretry(&xtime_lock, seq));
 
diff --git a/kernel/timer.c b/kernel/timer.c
index aeb6a54f2771..9199f3c52215 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -319,6 +319,24 @@ unsigned long round_jiffies_up_relative(unsigned long j)
 }
 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
 
+/**
+ * set_timer_slack - set the allowed slack for a timer
+ * @slack_hz: the amount of time (in jiffies) allowed for rounding
+ *
+ * Set the amount of time, in jiffies, that a certain timer has
+ * in terms of slack. By setting this value, the timer subsystem
+ * will schedule the actual timer somewhere between
+ * the time mod_timer() asks for, and that time plus the slack.
+ *
+ * By setting the slack to -1, a percentage of the delay is used
+ * instead.
+ */
+void set_timer_slack(struct timer_list *timer, int slack_hz)
+{
+        timer->slack = slack_hz;
+}
+EXPORT_SYMBOL_GPL(set_timer_slack);
+
 
 static inline void set_running_timer(struct tvec_base *base,
                                         struct timer_list *timer)
@@ -550,6 +568,7 @@ static void __init_timer(struct timer_list *timer,
 {
         timer->entry.next = NULL;
         timer->base = __raw_get_cpu_var(tvec_bases);
+        timer->slack = -1;
 #ifdef CONFIG_TIMER_STATS
         timer->start_site = NULL;
         timer->start_pid = -1;
@@ -715,6 +734,41 @@ int mod_timer_pending(struct timer_list *timer, unsigned long expires)
 }
 EXPORT_SYMBOL(mod_timer_pending);
 
+/*
+ * Decide where to put the timer while taking the slack into account
+ *
+ * Algorithm:
+ *   1) calculate the maximum (absolute) time
+ *   2) calculate the highest bit where the expires and new max are different
+ *   3) use this bit to make a mask
+ *   4) use the bitmask to round down the maximum time, so that all last
+ *      bits are zeros
+ */
+static inline
+unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
+{
+        unsigned long expires_limit, mask;
+        int bit;
+
+        expires_limit = expires + timer->slack;
+
+        if (timer->slack < 0) /* auto slack: use 0.4% */
+                expires_limit = expires + (expires - jiffies)/256;
+
+        mask = expires ^ expires_limit;
+
+        if (mask == 0)
+                return expires;
+
+        bit = find_last_bit(&mask, BITS_PER_LONG);
+
+        mask = (1 << bit) - 1;
+
+        expires_limit = expires_limit & ~(mask);
+
+        return expires_limit;
+}
+
 /**
  * mod_timer - modify a timer's timeout
  * @timer: the timer to be modified
@@ -745,6 +799,8 @@ int mod_timer(struct timer_list *timer, unsigned long expires)
         if (timer_pending(timer) && timer->expires == expires)
                 return 1;
 
+        expires = apply_slack(timer, expires);
+
         return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
 }
 EXPORT_SYMBOL(mod_timer);
@@ -955,6 +1011,47 @@ static int cascade(struct tvec_base *base, struct tvec *tv, int index)
         return index;
 }
 
+static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
+                          unsigned long data)
+{
+        int preempt_count = preempt_count();
+
+#ifdef CONFIG_LOCKDEP
+        /*
+         * It is permissible to free the timer from inside the
+         * function that is called from it, this we need to take into
+         * account for lockdep too. To avoid bogus "held lock freed"
+         * warnings as well as problems when looking into
+         * timer->lockdep_map, make a copy and use that here.
+         */
+        struct lockdep_map lockdep_map = timer->lockdep_map;
+#endif
+        /*
+         * Couple the lock chain with the lock chain at
+         * del_timer_sync() by acquiring the lock_map around the fn()
+         * call here and in del_timer_sync().
+         */
+        lock_map_acquire(&lockdep_map);
+
+        trace_timer_expire_entry(timer);
+        fn(data);
+        trace_timer_expire_exit(timer);
+
+        lock_map_release(&lockdep_map);
+
+        if (preempt_count != preempt_count()) {
+                WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
+                          fn, preempt_count, preempt_count());
+                /*
+                 * Restore the preempt count. That gives us a decent
+                 * chance to survive and extract information. If the
+                 * callback kept a lock held, bad luck, but not worse
+                 * than the BUG() we had.
+                 */
+                preempt_count() = preempt_count;
+        }
+}
+
 #define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
 
 /**
@@ -998,45 +1095,7 @@ static inline void __run_timers(struct tvec_base *base)
                         detach_timer(timer, 1);
 
                         spin_unlock_irq(&base->lock);
-                        {
-                                int preempt_count = preempt_count();
-
-#ifdef CONFIG_LOCKDEP
-                                /*
-                                 * It is permissible to free the timer from
-                                 * inside the function that is called from
-                                 * it, this we need to take into account for
-                                 * lockdep too. To avoid bogus "held lock
-                                 * freed" warnings as well as problems when
-                                 * looking into timer->lockdep_map, make a
-                                 * copy and use that here.
-                                 */
-                                struct lockdep_map lockdep_map =
-                                        timer->lockdep_map;
-#endif
-                                /*
-                                 * Couple the lock chain with the lock chain at
-                                 * del_timer_sync() by acquiring the lock_map
-                                 * around the fn() call here and in
-                                 * del_timer_sync().
-                                 */
-                                lock_map_acquire(&lockdep_map);
-
-                                trace_timer_expire_entry(timer);
-                                fn(data);
-                                trace_timer_expire_exit(timer);
-
-                                lock_map_release(&lockdep_map);
-
-                                if (preempt_count != preempt_count()) {
-                                        printk(KERN_ERR "huh, entered %p "
-                                               "with preempt_count %08x, exited"
-                                               " with %08x?\n",
-                                               fn, preempt_count,
-                                               preempt_count());
-                                        BUG();
-                                }
-                        }
+                        call_timer_fn(timer, fn, data);
                         spin_lock_irq(&base->lock);
                 }
         }