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From d8e6489cea6c5961626031a9191453f0aafc3085 Mon Sep 17 00:00:00 2001
From: Carsten Emde <C.Emde@osadl.org>
Date: Wed, 11 Jul 2012 22:05:18 +0000
Subject: [PATCH 253/271] Latency histograms: Adjust timer, if already elapsed
when programmed
Nothing prevents a programmer from calling clock_nanosleep() with an
already elapsed wakeup time in absolute time mode or with a too small
delay in relative time mode. Such timers cannot wake up in time and,
thus, should be corrected when entered into the missed timers latency
histogram (CONFIG_MISSED_TIMERS_HIST).
This patch marks such timers and uses a corrected expiration time.
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
include/linux/hrtimer.h | 3 +++
kernel/hrtimer.c | 16 ++++++++++++++--
2 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 26b008b..7259cd3 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -113,6 +113,9 @@ struct hrtimer {
unsigned long state;
struct list_head cb_entry;
int irqsafe;
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+ ktime_t praecox;
+#endif
#ifdef CONFIG_TIMER_STATS
int start_pid;
void *start_site;
diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 3848761..bca6928 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1031,6 +1031,17 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
#endif
}
+#ifdef CONFIG_MISSED_TIMER_OFFSETS_HIST
+ {
+ ktime_t now = new_base->get_time();
+
+ if (ktime_to_ns(tim) < ktime_to_ns(now))
+ timer->praecox = now;
+ else
+ timer->praecox = ktime_set(0, 0);
+ }
+#endif
+
hrtimer_set_expires_range_ns(timer, tim, delta_ns);
timer_stats_hrtimer_set_start_info(timer);
@@ -1467,8 +1478,9 @@ retry:
timer = container_of(node, struct hrtimer, node);
trace_hrtimer_interrupt(raw_smp_processor_id(),
- ktime_to_ns(ktime_sub(
- hrtimer_get_expires(timer), basenow)),
+ ktime_to_ns(ktime_sub(ktime_to_ns(timer->praecox) ?
+ timer->praecox : hrtimer_get_expires(timer),
+ basenow)),
current,
timer->function == hrtimer_wakeup ?
container_of(timer, struct hrtimer_sleeper,
--
1.7.10.4
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