1 files changed, 57 insertions, 40 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index ede527708123..931a4d99bc55 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -557,7 +557,7 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
 static int hrtimer_reprogram(struct hrtimer *timer,
                              struct hrtimer_clock_base *base)
 {
-        ktime_t *expires_next = &__get_cpu_var(hrtimer_bases).expires_next;
+        struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
         ktime_t expires = ktime_sub(hrtimer_get_expires(timer), base->offset);
         int res;
 
@@ -582,7 +582,16 @@ static int hrtimer_reprogram(struct hrtimer *timer,
         if (expires.tv64 < 0)
                 return -ETIME;
 
-        if (expires.tv64 >= expires_next->tv64)
+        if (expires.tv64 >= cpu_base->expires_next.tv64)
+                return 0;
+
+        /*
+         * If a hang was detected in the last timer interrupt then we
+         * do not schedule a timer which is earlier than the expiry
+         * which we enforced in the hang detection. We want the system
+         * to make progress.
+         */
+        if (cpu_base->hang_detected)
                 return 0;
 
         /*
@@ -590,7 +599,7 @@ static int hrtimer_reprogram(struct hrtimer *timer,
          */
         res = tick_program_event(expires, 0);
         if (!IS_ERR_VALUE(res))
-                *expires_next = expires;
+                cpu_base->expires_next = expires;
         return res;
 }
 
@@ -1217,30 +1226,6 @@ static void __run_hrtimer(struct hrtimer *timer, ktime_t *now)
 
 #ifdef CONFIG_HIGH_RES_TIMERS
 
-static int force_clock_reprogram;
-
-/*
- * After 5 iteration's attempts, we consider that hrtimer_interrupt()
- * is hanging, which could happen with something that slows the interrupt
- * such as the tracing. Then we force the clock reprogramming for each future
- * hrtimer interrupts to avoid infinite loops and use the min_delta_ns
- * threshold that we will overwrite.
- * The next tick event will be scheduled to 3 times we currently spend on
- * hrtimer_interrupt(). This gives a good compromise, the cpus will spend
- * 1/4 of their time to process the hrtimer interrupts. This is enough to
- * let it running without serious starvation.
- */
-
-static inline void
-hrtimer_interrupt_hanging(struct clock_event_device *dev,
-                        ktime_t try_time)
-{
-        force_clock_reprogram = 1;
-        dev->min_delta_ns = (unsigned long)try_time.tv64 * 3;
-        printk(KERN_WARNING "hrtimer: interrupt too slow, "
-               "forcing clock min delta to %llu ns\n",
-               (unsigned long long) dev->min_delta_ns);
-}
 /*
  * High resolution timer interrupt
  * Called with interrupts disabled
@@ -1249,21 +1234,15 @@ void hrtimer_interrupt(struct clock_event_device *dev)
 {
         struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
         struct hrtimer_clock_base *base;
-        ktime_t expires_next, now;
-        int nr_retries = 0;
-        int i;
+        ktime_t expires_next, now, entry_time, delta;
+        int i, retries = 0;
 
         BUG_ON(!cpu_base->hres_active);
         cpu_base->nr_events++;
         dev->next_event.tv64 = KTIME_MAX;
 
- retry:
-        /* 5 retries is enough to notice a hang */
-        if (!(++nr_retries % 5))
-                hrtimer_interrupt_hanging(dev, ktime_sub(ktime_get(), now));
-
-        now = ktime_get();
-
+        entry_time = now = ktime_get();
+retry:
         expires_next.tv64 = KTIME_MAX;
 
         spin_lock(&cpu_base->lock);
@@ -1325,10 +1304,48 @@ void hrtimer_interrupt(struct clock_event_device *dev)
         spin_unlock(&cpu_base->lock);
 
         /* Reprogramming necessary ? */
-        if (expires_next.tv64 != KTIME_MAX) {
-                if (tick_program_event(expires_next, force_clock_reprogram))
-                        goto retry;
+        if (expires_next.tv64 == KTIME_MAX ||
+            !tick_program_event(expires_next, 0)) {
+                cpu_base->hang_detected = 0;
+                return;
         }
+
+        /*
+         * The next timer was already expired due to:
+         * - tracing
+         * - long lasting callbacks
+         * - being scheduled away when running in a VM
+         *
+         * We need to prevent that we loop forever in the hrtimer
+         * interrupt routine. We give it 3 attempts to avoid
+         * overreacting on some spurious event.
+         */
+        now = ktime_get();
+        cpu_base->nr_retries++;
+        if (++retries < 3)
+                goto retry;
+        /*
+         * Give the system a chance to do something else than looping
+         * here. We stored the entry time, so we know exactly how long
+         * we spent here. We schedule the next event this amount of
+         * time away.
+         */
+        cpu_base->nr_hangs++;
+        cpu_base->hang_detected = 1;
+        delta = ktime_sub(now, entry_time);
+        if (delta.tv64 > cpu_base->max_hang_time.tv64)
+                cpu_base->max_hang_time = delta;
+        /*
+         * Limit it to a sensible value as we enforce a longer
+         * delay. Give the CPU at least 100ms to catch up.
+         */
+        if (delta.tv64 > 100 * NSEC_PER_MSEC)
+                expires_next = ktime_add_ns(now, 100 * NSEC_PER_MSEC);
+        else
+                expires_next = ktime_add(now, delta);
+        tick_program_event(expires_next, 1);
+        printk_once(KERN_WARNING "hrtimer: interrupt took %llu ns\n",
+                    ktime_to_ns(delta));
 }
 
 /*