[PATCH] ia64 printk_clock()

From: Luck, Tony <tony.luck_at_intel.com>
Date: 2005-09-23 02:41:15
Linus just took a patch from Andrew that allows architectures to
override the clock used for time-stamping kernel printk().  Ia64
needs to override for two reasons:

1) default printk_clock() uses sched_clock() which accesses per-cpu
   variables ... this means the kernel crashes on an early printk
   before the per-cpu mapping is set up.

2) sched_clock() is based on ar.itc which some systems do not keep
   synchronized, so printk() timestamps jump about as different cpus
   print messages.

Here is a trivial printk_clock() based on jiffies, so we get much less
resolution in exchange for correctness.  I'd be happy to see a better
version that does interpolation (but remember that you can't take
locks or access per-cpu variables).


Signed-off-by: Tony Luck <tony.luck@intel.com>

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -253,3 +253,9 @@ time_init (void)
 	set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
+unsigned long long printk_clock(void)
+	return (unsigned long long)(jiffies_64 - INITIAL_JIFFIES)*(1000000000/HZ);
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Received on Fri Sep 23 02:42:19 2005

This archive was generated by hypermail 2.1.8 : 2005-09-23 02:42:26 EST