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@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
include/linux/hrtimer.h | 3 +++
kernel/hrtimer.c | 16 ++++++++++++++--
2 files changed, 17 insertions(+), 2 deletions(-)
Index: linux-3.4.2-rt10-64+/include/linux/hrtimer.h
===================================================================
--- linux-3.4.2-rt10-64+.orig/include/linux/hrtimer.h
+++ linux-3.4.2-rt10-64+/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;
Index: linux-3.4.2-rt10-64+/kernel/hrtimer.c
===================================================================
--- linux-3.4.2-rt10-64+.orig/kernel/hrtimer.c
+++ linux-3.4.2-rt10-64+/kernel/hrtimer.c
@@ -1021,6 +1021,17 @@ int __hrtimer_start_range_ns(struct hrti
#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);
@@ -1458,8 +1469,9 @@ 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,
--
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