linux-kernel - Re: [PATCH 4/6] RTC: Ratelimit "lost interrupts" message

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Message-Id: <20070524140956.12ff7c99.akpm@linux-foundation.org>
Date:	Thu, 24 May 2007 14:09:56 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ben Collins <ben.collins@...ntu.com>
Cc:	linux-kernel@...r.kernel.org, Zachary Amsden <zach@...are.com>
Subject: Re: [PATCH 4/6] RTC: Ratelimit "lost interrupts" message

On Thu, 24 May 2007 16:56:52 -0400
Ben Collins <ben.collins@...ntu.com> wrote:

> On Thu, 2007-05-24 at 13:48 -0700, Andrew Morton wrote:
> > On Wed, 23 May 2007 18:23:06 -0400
> > Ben Collins <bcollins@...ntu.com> wrote:
> > 
> > > Signed-off-by: Ben Collins <bcollins@...ntu.com>
> > > ---
> > >  drivers/char/rtc.c |    3 ++-
> > >  1 files changed, 2 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/drivers/char/rtc.c b/drivers/char/rtc.c
> > > index 20380a2..22cf7aa 100644
> > > --- a/drivers/char/rtc.c
> > > +++ b/drivers/char/rtc.c
> > > @@ -1159,7 +1159,8 @@ static void rtc_dropped_irq(unsigned long data)
> > >  
> > >  	spin_unlock_irq(&rtc_lock);
> > >  
> > > -	printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n", freq);
> > > +	if (printk_ratelimit())
> > > +		printk(KERN_WARNING "rtc: lost some interrupts at %ldHz.\n", freq);
> > >  
> > 
> > Presumably someone is getting a lot of these messages.
> > 
> > Do we know why?  Is there something which needs fixing here?
> 
> I got it a lot when using any sort of virtualization on my Core2Duo
> (kvm, vmware, qemu). Just a big spew. Honestly, I was getting this with
> 2.6.20, and haven't tested again with latest kernel.

OK, a bit of googling finds things like this:
http://chxo.com/be2/20060821_3333.html, so I assume that it's some sort of
generic problem with the hypervisor's emulation of the RTC.

Zach, do you know what the score is here?

Thanks.
-
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