hrtimer: removing all ur callback modes, fix hotplug

Impact: fix hrtimer locking (reported by lockdep) in the CPU hotplug case

This addition fixes the hotplug locking issue on my machine

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 37 insertions, 28 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index efd6f41e1c16..b09c7a27631d 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1496,7 +1496,7 @@ static void __cpuinit init_hrtimers_cpu(int cpu)
 #ifdef CONFIG_HOTPLUG_CPU
 
 static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
-                                 struct hrtimer_clock_base *new_base, int dcpu)
+                                struct hrtimer_clock_base *new_base)
 {
         struct hrtimer *timer;
         struct rb_node *node;
@@ -1514,40 +1514,34 @@ static void 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) {
-                        /* XXX: running on offline cpu */
-                        __run_hrtimer(timer);
-                }
-#endif
                 /* Clear the migration state bit */
                 timer->state &= ~HRTIMER_STATE_MIGRATE;
         }
 }
 
-static void migrate_hrtimers(int cpu)
+static int migrate_hrtimers(int scpu)
 {
         struct hrtimer_cpu_base *old_base, *new_base;
-        int i;
+        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.
@@ -1557,32 +1551,47 @@ static void migrate_hrtimers(int cpu)
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
                 migrate_hrtimer_list(&old_base->clock_base[i],
-                                     &new_base->clock_base[i], cpu);
+                                     &new_base->clock_base[i]);
         }
 
         spin_unlock(&old_base->lock);
         spin_unlock_irq(&new_base->lock);
         put_cpu_var(hrtimer_bases);
+
+        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 dcpu = -1, 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);
+                clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &scpu);
+                dcpu = migrate_hrtimers(scpu);
+                break;
+
+        case CPU_POST_DEAD:
+                if (dcpu == -1)
+                        break;
+
+                smp_call_function_single(dcpu, tickle_timers, NULL, 0);
                 break;
 #endif