Merge branch 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent

Merge RCU fixes from Paul E. McKenney:

 " This series has four patches, the major point of which is to eliminate
   some slowdowns (including boot-time slowdowns) resulting from some
   RCU_FAST_NO_HZ changes.  The issue with the changes is that posting timers
   from the idle loop has no effect if the CPU has entered dyntick-idle
   mode because the CPU has already computed its wakeup time, and posting
   a timer does not cause it to be recomputed.  The short-term fix is for
   RCU to precompute the timeout value so that the CPU's calculation is
   correct. "

Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da70c6db496c..869997833928 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -274,6 +274,7 @@ EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
 static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
 {
         unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
+        unsigned long rcu_delta_jiffies;
         ktime_t last_update, expires, now;
         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
         u64 time_delta;
@@ -322,7 +323,7 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
                 time_delta = timekeeping_max_deferment();
         } while (read_seqretry(&xtime_lock, seq));
 
-        if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu) ||
+        if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) || printk_needs_cpu(cpu) ||
             arch_needs_cpu(cpu)) {
                 next_jiffies = last_jiffies + 1;
                 delta_jiffies = 1;
@@ -330,6 +331,10 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
                 /* Get the next timer wheel timer */
                 next_jiffies = get_next_timer_interrupt(last_jiffies);
                 delta_jiffies = next_jiffies - last_jiffies;
+                if (rcu_delta_jiffies < delta_jiffies) {
+                        next_jiffies = last_jiffies + rcu_delta_jiffies;
+                        delta_jiffies = rcu_delta_jiffies;
+                }
         }
         /*
          * Do not stop the tick, if we are only one off