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-rw-r--r--kernel/hrtimer.c30
1 files changed, 29 insertions, 1 deletions
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index f33afb0407b..8fea312ca36 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1158,6 +1158,29 @@ static void __run_hrtimer(struct hrtimer *timer)
#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 %lu ns\n", dev->min_delta_ns);
+}
/*
* High resolution timer interrupt
* Called with interrupts disabled
@@ -1167,6 +1190,7 @@ 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;
BUG_ON(!cpu_base->hres_active);
@@ -1174,6 +1198,10 @@ void hrtimer_interrupt(struct clock_event_device *dev)
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();
expires_next.tv64 = KTIME_MAX;
@@ -1226,7 +1254,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
/* Reprogramming necessary ? */
if (expires_next.tv64 != KTIME_MAX) {
- if (tick_program_event(expires_next, 0))
+ if (tick_program_event(expires_next, force_clock_reprogram))
goto retry;
}
}