linux-kernel - Re: 3.0.0-rc2: Xen: powernow-k8: Kernel panic

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Date:	Tue, 14 Jun 2011 01:52:21 +0200
From:	Tobias Diedrich <ranma+xen@...edrich.de>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	xen-users@...ts.xensource.com, linux-kernel@...r.kernel.org
Subject: Re: 3.0.0-rc2: Xen: powernow-k8: Kernel panic - not syncing:
 Attempted to kill init!

Konrad Rzeszutek Wilk wrote:
> > [    5.523199] rtc_cmos 00:05: setting system clock to 2011-06-13 20:20:00 UTC (1307996400)
> > [    5.523400] powernow-k8: Found 1 AMD Athlon(tm) 64 Processor 3700+ (1 cpu cores) (version 2.20.00)
> > [    5.530956] powernow-k8: fid 0x2 (1000 MHz), vid 0x12
> > [    5.531072] powernow-k8: fid 0xa (1800 MHz), vid 0xa
> > [    5.531187] powernow-k8: fid 0xc (2000 MHz), vid 0x8
> > [    5.531301] powernow-k8: fid 0xe (2200 MHz), vid 0x8
> > [    5.531460] Marking TSC unstable due to cpufreq changes
> > [    5.531680] powernow-k8: fid trans failed, fid 0x2, curr 0x0
> > [    5.531802] BUG: unable to handle kernel paging request at ffff880807e07b78
> > [    5.531982] IP: [<ffffffff81479163>] cpufreq_stats_update+0x46/0x5b
> 
> For this one, you will have to fire out gdb and disassemble the code to
> figure out where it failed. Look for 'gdb vmlinux' and 'disassembly' on this
> mailing list - that should provide some hints.

Probably because of the 'fid trans failed' stat->last_index is -1
(or 0xffffffff because it's really an unsigned int):
[    5.721794] powernow-k8: fid trans failed, fid 0xa, curr 0x0
[    5.721909] cpufreq_stats_update: cpu=0 
[    5.721945]  max_state=4 last_index=-1
[    5.722191] ------------[ cut here ]------------
[    5.722305] kernel BUG at drivers/cpufreq/cpufreq_stats.c:71!

I added the BUG() there:
if (stat->last_index > stat->max_state * stat->max_state) BUG();

Index: linux-3.0-rc2-xen/drivers/cpufreq/cpufreq_stats.c
===================================================================
--- linux-3.0-rc2-xen.orig/drivers/cpufreq/cpufreq_stats.c	2011-06-14 01:24:10.639010391 +0200
+++ linux-3.0-rc2-xen/drivers/cpufreq/cpufreq_stats.c	2011-06-14 01:32:32.743101791 +0200
@@ -56,9 +56,20 @@
 	struct cpufreq_stats *stat;
 	unsigned long long cur_time;
 
+	printk(KERN_WARNING "cpufreq_stats_update: cpu=%d ", cpu);
+
+	if (cpu != 0) // only got one cpu in this particular system
+		BUG();
+
 	cur_time = get_jiffies_64();
 	spin_lock(&cpufreq_stats_lock);
 	stat = per_cpu(cpufreq_stats_table, cpu);
+
+	printk(KERN_WARNING " max_state=%d last_index=%d\n", stat->max_state, stat->last_index);
+
+	if (stat->last_index > stat->max_state * stat->max_state)
+		BUG();
+
 	if (stat->time_in_state)
 		stat->time_in_state[stat->last_index] =
 			cputime64_add(stat->time_in_state[stat->last_index],

-- 
Tobias						PGP: http://8ef7ddba.uguu.de
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