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

Pull timer fixes from Thomas Gleixner:
 "A pile of fixes for long standing issues with the timer wheel and the
  NOHZ code:

   - Prevent timer base confusion accross the nohz switch, which can
     cause unlocked access and data corruption

   - Reinitialize the stale base clock on cpu hotplug to prevent subtle
     side effects including rollovers on 32bit

   - Prevent an interrupt storm when the timer softirq is already
     pending caused by tick_nohz_stop_sched_tick()

   - Move the timer start tracepoint to a place where it actually makes
     sense

   - Add documentation to timerqueue functions as they caused confusion
     several times now"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timerqueue: Document return values of timerqueue_add/del()
  timers: Invoke timer_start_debug() where it makes sense
  nohz: Prevent a timer interrupt storm in tick_nohz_stop_sched_tick()
  timers: Reinitialize per cpu bases on hotplug
  timers: Use deferrable base independent of base::nohz_active

1 files changed, 24 insertions, 11 deletions

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index ffebcf878fba..89a9e1b4264a 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -823,11 +823,10 @@ static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
         struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
 
         /*
-         * If the timer is deferrable and nohz is active then we need to use
-         * the deferrable base.
+         * If the timer is deferrable and NO_HZ_COMMON is set then we need
+         * to use the deferrable base.
          */
-        if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active &&
-            (tflags & TIMER_DEFERRABLE))
+        if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
                 base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
         return base;
 }
@@ -837,11 +836,10 @@ static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
         struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
 
         /*
-         * If the timer is deferrable and nohz is active then we need to use
-         * the deferrable base.
+         * If the timer is deferrable and NO_HZ_COMMON is set then we need
+         * to use the deferrable base.
          */
-        if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active &&
-            (tflags & TIMER_DEFERRABLE))
+        if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
                 base = this_cpu_ptr(&timer_bases[BASE_DEF]);
         return base;
 }
@@ -1009,8 +1007,6 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
         if (!ret && (options & MOD_TIMER_PENDING_ONLY))
                 goto out_unlock;
 
-        debug_activate(timer, expires);
-
         new_base = get_target_base(base, timer->flags);
 
         if (base != new_base) {
@@ -1034,6 +1030,8 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option
                 }
         }
 
+        debug_activate(timer, expires);
+
         timer->expires = expires;
         /*
          * If 'idx' was calculated above and the base time did not advance
@@ -1684,7 +1682,7 @@ static __latent_entropy void run_timer_softirq(struct softirq_action *h)
         base->must_forward_clk = false;
 
         __run_timers(base);
-        if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && base->nohz_active)
+        if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
                 __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
 }
 
@@ -1855,6 +1853,21 @@ static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *h
         }
 }
 
+int timers_prepare_cpu(unsigned int cpu)
+{
+        struct timer_base *base;
+        int b;
+
+        for (b = 0; b < NR_BASES; b++) {
+                base = per_cpu_ptr(&timer_bases[b], cpu);
+                base->clk = jiffies;
+                base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
+                base->is_idle = false;
+                base->must_forward_clk = true;
+        }
+        return 0;
+}
+
 int timers_dead_cpu(unsigned int cpu)
 {
         struct timer_base *old_base;