Re: broken timer

[Gleb Natapov <gleb@redhat.com>]

On Mon, Jul 27, 2009 at 03:05:40PM -0300, Glauber Costa wrote:
> Hello, goodfellas
> 
> I'm seeing a strange problem in our much loved qemu-kvm.git
This bug shouldn't depend on qemu-kvm.git at all unless you are running
with no-kvm-irqchip. The only things that involved in APIC timer
calibration are tsc and APIC. (If you don't use apicpmtimer kernel
parameter. Don't you?)

What is you host HW? Which version of kernel modules are you using?
Is your host overcommitted when this happens? Try to load the host with
work (while(1)) and run the guest. Is it easier to reproduce problem
this way?

> It's been there before avi left for vacation, at least.
> 
> The worst part, is that it doesn't happen always, and I don't
> even think it is deterministic in its nature, IOW, there was nothing
> I could do to make it more or less likely to happen.
> 
> It's almost obviously interrupt related, but I can't determine more than that
> As I haven't, and won't have the time to debug this in the near future, here's
> the riddle for you all to appreciate:
> 
> ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1                                                                                                         
> CPU0: QEMU Virtual CPU version 0.10.50 stepping 03                                                                                                           
> Using local APIC timer interrupts.                                                                                                                           
> Detected 0.000 MHz APIC timer.                                                                                                                               
> ------------[ cut here ]------------                                                                                                                         
> WARNING: at kernel/time/clockevents.c:46 clockevent_delta2ns+0x37/0x72() (Not tainted)                                                                       
> Modules linked in:                                                                                                                                           
> Pid: 1, comm: swapper Not tainted 2.6.27.5-117.fc10.x86_64 #1                                                                                                
> 
> Call Trace:
>  [<ffffffff810418f2>] warn_on_slowpath+0x60/0x90
>  [<ffffffff81331c7e>] ? trace_hardirqs_on_thunk+0x3a/0x3c
>  [<ffffffff8159d140>] ? early_idt_handler+0x0/0x72       
>  [<ffffffff8132faf6>] ? printk+0x3c/0x3e                 
>  [<ffffffff8105cb9a>] clockevent_delta2ns+0x37/0x72      
>  [<ffffffff815ad263>] setup_boot_APIC_clock+0x1c2/0x24b  
>  [<ffffffff8132faf6>] ? printk+0x3c/0x3e                 
>  [<ffffffff815ab8a6>] native_smp_prepare_cpus+0x29e/0x2cf
>  [<ffffffff8159d5a8>] kernel_init+0x59/0x214             
>  [<ffffffff81331c7e>] ? trace_hardirqs_on_thunk+0x3a/0x3c
>  [<ffffffff810116e9>] child_rip+0xa/0x11                 
>  [<ffffffff81010a07>] ? restore_args+0x0/0x30            
>  [<ffffffff8159d54f>] ? kernel_init+0x0/0x214            
>  [<ffffffff810116df>] ? child_rip+0x0/0x11
> 
> ---[ end trace 4eaa2a86a8e2da22 ]---
> APIC frequency too slow, disabling apic timer
> 
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--
			Gleb.