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:
  Documentation: Add timers/timers-howto.txt
  timer: Added usleep_range timer
  Revert "timer: Added usleep[_range] timer"
  clockevents: Remove the per cpu tick skew
  posix_timer: Move copy_to_user(created_timer_id) down in timer_create()
  timer: Added usleep[_range] timer
  timers: Document meaning of deferrable timer

3 files changed, 35 insertions, 12 deletions

diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
index ad723420acc3..9ca4973f736d 100644
--- a/kernel/posix-timers.c
+++ b/kernel/posix-timers.c
@@ -560,11 +560,6 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
         new_timer->it_clock = which_clock;
         new_timer->it_overrun = -1;
 
-        if (copy_to_user(created_timer_id,
-                         &new_timer_id, sizeof (new_timer_id))) {
-                error = -EFAULT;
-                goto out;
-        }
         if (timer_event_spec) {
                 if (copy_from_user(&event, timer_event_spec, sizeof (event))) {
                         error = -EFAULT;
@@ -590,6 +585,12 @@ SYSCALL_DEFINE3(timer_create, const clockid_t, which_clock,
         new_timer->sigq->info.si_tid   = new_timer->it_id;
         new_timer->sigq->info.si_code  = SI_TIMER;
 
+        if (copy_to_user(created_timer_id,
+                         &new_timer_id, sizeof (new_timer_id))) {
+                error = -EFAULT;
+                goto out;
+        }
+
         error = CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
         if (error)
                 goto out;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 021d2f878f19..3e216e01bbd1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -774,7 +774,6 @@ void tick_setup_sched_timer(void)
 {
         struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
         ktime_t now = ktime_get();
-        u64 offset;
 
         /*
          * Emulate tick processing via per-CPU hrtimers:
@@ -784,10 +783,6 @@ void tick_setup_sched_timer(void)
 
         /* Get the next period (per cpu) */
         hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
-        offset = ktime_to_ns(tick_period) >> 1;
-        do_div(offset, num_possible_cpus());
-        offset *= smp_processor_id();
-        hrtimer_add_expires_ns(&ts->sched_timer, offset);
 
         for (;;) {
                 hrtimer_forward(&ts->sched_timer, now, tick_period);
diff --git a/kernel/timer.c b/kernel/timer.c
index d61d16da0b64..f1b8afe1ad86 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -90,8 +90,13 @@ static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
 
 /*
  * Note that all tvec_bases are 2 byte aligned and lower bit of
- * base in timer_list is guaranteed to be zero. Use the LSB for
- * the new flag to indicate whether the timer is deferrable
+ * base in timer_list is guaranteed to be zero. Use the LSB to
+ * indicate whether the timer is deferrable.
+ *
+ * A deferrable timer will work normally when the system is busy, but
+ * will not cause a CPU to come out of idle just to service it; instead,
+ * the timer will be serviced when the CPU eventually wakes up with a
+ * subsequent non-deferrable timer.
  */
 #define TBASE_DEFERRABLE_FLAG           (0x1)
 
@@ -1758,3 +1763,25 @@ unsigned long msleep_interruptible(unsigned int msecs)
 }
 
 EXPORT_SYMBOL(msleep_interruptible);
+
+static int __sched do_usleep_range(unsigned long min, unsigned long max)
+{
+        ktime_t kmin;
+        unsigned long delta;
+
+        kmin = ktime_set(0, min * NSEC_PER_USEC);
+        delta = (max - min) * NSEC_PER_USEC;
+        return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
+}
+
+/**
+ * usleep_range - Drop in replacement for udelay where wakeup is flexible
+ * @min: Minimum time in usecs to sleep
+ * @max: Maximum time in usecs to sleep
+ */
+void usleep_range(unsigned long min, unsigned long max)
+{
+        __set_current_state(TASK_UNINTERRUPTIBLE);
+        do_usleep_range(min, max);
+}
+EXPORT_SYMBOL(usleep_range);