linux-kernel - Re: CONFIG_PRINTK_TIME broken on git HEAD ?

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Date:	Fri, 09 May 2008 11:39:33 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Gabriel C <nix.or.die@...glemail.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: CONFIG_PRINTK_TIME broken on git HEAD ?

On Thu, 2008-05-08 at 13:21 +0200, Gabriel C wrote:

> > Ok, so the issue is that the clock doesn't start at 0, but at:
> > 4294014.506571 ?
> 
> At least on my box , yes.
> 

Does this work for you?

---

Subject: sched: fixup sched-clock offset
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>

It could happen that ktime doesn't start at 0.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 kernel/sched_clock.c |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

Index: linux-2.6-2/kernel/sched_clock.c
===================================================================
--- linux-2.6-2.orig/kernel/sched_clock.c
+++ linux-2.6-2/kernel/sched_clock.c
@@ -59,21 +59,23 @@ static inline struct sched_clock_data *c
 	return &per_cpu(sched_clock_data, cpu);
 }
 
+static __read_mostly u64 ktime_offset;
+
 void sched_clock_init(void)
 {
-	u64 ktime_now = ktime_to_ns(ktime_get());
-	u64 now = 0;
 	int cpu;
 
+	ktime_offset = ktime_to_ns(ktime_get());
+
 	for_each_possible_cpu(cpu) {
 		struct sched_clock_data *scd = cpu_sdc(cpu);
 
 		scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
 		scd->prev_jiffies = jiffies;
-		scd->prev_raw = now;
-		scd->tick_raw = now;
-		scd->tick_gtod = ktime_now;
-		scd->clock = ktime_now;
+		scd->prev_raw = 0;
+		scd->tick_raw = 0;
+		scd->tick_gtod = 0;
+		scd->clock = 0;
 	}
 }
 
@@ -177,7 +179,7 @@ void sched_clock_tick(void)
 	WARN_ON_ONCE(!irqs_disabled());
 
 	now = sched_clock();
-	now_gtod = ktime_to_ns(ktime_get());
+	now_gtod = ktime_to_ns(ktime_get()) - ktime_offset;
 
 	__raw_spin_lock(&scd->lock);
 	__update_sched_clock(scd, now);


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