On 07.11.13, Thomas Gleixner wrote:
> below should address that issue. If that works on mainline we can
> adapt it for RT (needs a trylock(&base->lock) there).
okay, so this is waht I'm going to take for -RT:
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 79a7a35..bdbf77db 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -461,9 +461,8 @@ extern int schedule_hrtimeout_range_clock(ktime_t *expires,
unsigned long delta, const enum hrtimer_mode mode, int clock);
extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
-/* Soft interrupt function to run the hrtimer queues: */
+/* Called from the periodic timer tick */
extern void hrtimer_run_queues(void);
-extern void hrtimer_run_pending(void);
/* Bootup initialization: */
extern void __init hrtimers_init(void);
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index c383841..7aa442e 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1694,30 +1694,6 @@ static void run_hrtimer_softirq(struct softirq_action *h)
}
/*
- * Called from timer softirq every jiffy, expire hrtimers:
- *
- * For HRT its the fall back code to run the softirq in the timer
- * softirq context in case the hrtimer initialization failed or has
- * not been done yet.
- */
-void hrtimer_run_pending(void)
-{
- if (hrtimer_hres_active())
- return;
-
- /*
- * This _is_ ugly: We have to check in the softirq context,
- * whether we can switch to highres and / or nohz mode. The
- * clocksource switch happens in the timer interrupt with
- * xtime_lock held. Notification from there only sets the
- * check bit in the tick_oneshot code, otherwise we might
- * deadlock vs. xtime_lock.
- */
- if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
- hrtimer_switch_to_hres();
-}
-
-/*
* Called from hardirq context every jiffy
*/
void hrtimer_run_queues(void)
@@ -1730,6 +1706,13 @@ void hrtimer_run_queues(void)
if (hrtimer_hres_active())
return;
+ /*
+ * Check whether we can switch to highres mode.
+ */
+ if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())
+ && hrtimer_switch_to_hres())
+ return;
+
for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
base = &cpu_base->clock_base[index];
if (!timerqueue_getnext(&base->active))
diff --git a/kernel/timer.c b/kernel/timer.c
index b06c647..46467be 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1443,8 +1443,6 @@ static void run_timer_softirq(struct softirq_action *h)
irq_work_run();
#endif
- hrtimer_run_pending();
-
if (time_after_eq(jiffies, base->timer_jiffies))
__run_timers(base);
}
@@ -1454,8 +1452,27 @@ static void run_timer_softirq(struct softirq_action *h)
*/
void run_local_timers(void)
{
+ struct tvec_base *base = __this_cpu_read(tvec_bases);
+
hrtimer_run_queues();
- raise_softirq(TIMER_SOFTIRQ);
+ /*
+ * We can access this lockless as we are in the timer
+ * interrupt. If there are no timers queued, nothing to do in
+ * the timer softirq.
+ */
+ if (!spin_do_trylock(&base->lock)) {
+ raise_softirq(TIMER_SOFTIRQ);
+ return;
+ }
+ if (!base->active_timers)
+ goto out;
+
+ /* Check whether the next pending timer has expired */
+ if (time_before_eq(base->next_timer, jiffies))
+ raise_softirq(TIMER_SOFTIRQ);
+out:
+ rt_spin_unlock_after_trylock_in_irq(&base->lock);
+
}
#ifdef __ARCH_WANT_SYS_ALARM
--
1.8.5.1
Sebastian
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