* Stefano Brivio <[EMAIL PROTECTED]> wrote:
> This patch fixes a regression introduced by:
>
> commit bb29ab26863c022743143f27956cc0ca362f258c
> Author: Ingo Molnar <[EMAIL PROTECTED]>
> Date: Mon Jul 9 18:51:59 2007 +0200
>
> This caused the jiffies counter to leap back and forth on cpufreq
> changes on my x86 box. I'd say that we can't always assume that TSC
> does "small errors" only, when marked unstable. On cpufreq changes
> these errors can be huge.
ah, printk_clock() still uses sched_clock(), not jiffies. So it's not
the jiffies counter that goes back and forth, it's sched_clock() - so
this is a printk timestamps anomaly, not related to jiffies. I thought
we have fixed this bug in the printk code already: sched_clock() is a
'raw' interface that should not be used directly - the proper interface
is cpu_clock(cpu). Does the patch below help?
Ingo
----------------------->
Subject: sched: fix CONFIG_PRINT_TIME's reliance on sched_clock()
From: Ingo Molnar <[EMAIL PROTECTED]>
Stefano Brivio reported weird printk timestamp behavior during
CPU frequency changes:
http://bugzilla.kernel.org/show_bug.cgi?id=9475
fix CONFIG_PRINT_TIME's reliance on sched_clock() and use cpu_clock()
instead.
Reported-and-bisected-by: Stefano Brivio <[EMAIL PROTECTED]>
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
---
kernel/printk.c | 2 +-
kernel/sched.c | 7 ++++++-
2 files changed, 7 insertions(+), 2 deletions(-)
Index: linux/kernel/printk.c
===================================================================
--- linux.orig/kernel/printk.c
+++ linux/kernel/printk.c
@@ -680,7 +680,7 @@ asmlinkage int vprintk(const char *fmt,
loglev_char = default_message_loglevel
+ '0';
}
- t = printk_clock();
+ t = cpu_clock(printk_cpu);
nanosec_rem = do_div(t, 1000000000);
tlen = sprintf(tbuf,
"<%c>[%5lu.%06lu] ",
Index: linux/kernel/sched.c
===================================================================
--- linux.orig/kernel/sched.c
+++ linux/kernel/sched.c
@@ -599,7 +599,12 @@ unsigned long long cpu_clock(int cpu)
local_irq_save(flags);
rq = cpu_rq(cpu);
- update_rq_clock(rq);
+ /*
+ * Only call sched_clock() if the scheduler has already been
+ * initialized (some code might call cpu_clock() very early):
+ */
+ if (rq->idle)
+ update_rq_clock(rq);
now = rq->clock;
local_irq_restore(flags);
--
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