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From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
	linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Carsten Emde <C.Emde@osadl.org>, John Kacur <jkacur@redhat.com>
Subject: [PATCH RT 2/8] Latency histograms: Adjust timer, if already elapsed when programmed
Date: Thu, 12 Jul 2012 19:18:29 -0400	[thread overview]
Message-ID: <20120712231955.969926051@goodmis.org> (raw)
In-Reply-To: 20120712231827.084920483@goodmis.org

[-- Attachment #1: 0002-Latency-histograms-Adjust-timer-if-already-elapsed-w.patch --]
[-- Type: text/plain, Size: 2131 bytes --]

From: Carsten Emde <C.Emde@osadl.org>

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 0e37086..7408760 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 3991464..a080e62 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -1021,6 +1021,17 @@ 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);
@@ -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,
-- 
1.7.10.4



  parent reply	other threads:[~2012-07-12 23:20 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-07-12 23:18 [PATCH RT 0/8] [ANNOUNCE] 3.2.22-rt35-rc1 stable review Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 1/8] Latency histogramms: Cope with backwards running local trace clock Steven Rostedt
2012-07-12 23:18 ` Steven Rostedt [this message]
2012-07-12 23:18 ` [PATCH RT 3/8] Disable RT_GROUP_SCHED in PREEMPT_RT_FULL Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 4/8] Latency histograms: Detect another yet overlooked sharedprio condition Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 5/8] slab: Prevent local lock deadlock Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 6/8] fs, jbd: pull your plug when waiting for space Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 7/8] perf: Make swevent hrtimer run in irq instead of softirq Steven Rostedt
2012-07-12 23:18 ` [PATCH RT 8/8] Linux 3.2.22-rt35-rc1 Steven Rostedt

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