Timer interrupt lost on some x86_64 systems

Neil Horman nhorman at redhat.com
Tue Nov 13 09:33:30 EST 2007

On Tue, Nov 13, 2007 at 01:01:28PM +0530, Vivek Goyal wrote:
> On Mon, Nov 12, 2007 at 10:41:19AM -0500, Neil Horman wrote:
> [..]
> > 
> > 
> > Although, as I look at it, it would appear that time_init from start_kernel does
> > seem to init the hpet if its available, and it silently fails if that doesn't
> > work, moving on to the pmtimer and pit.  I wonder if there is some extra magic
> > to resetting the hpet to run on a different cpu for some systems...
> > Neil
> > 
> Any idea what kind of timer devices this motherborad has got? Which timer
> device gets activated in first kernel? Then we can focus on why the
> interrupts from same device are not coming in second kernel.

Not sure, thats a course of investigation I've got planned to pursue when our on
site guy gets back from a conference next week.

> In the past I have found issues with interrupt routing on IOPAPIC and
> interrupt lockup on LAPIC. But these issues are already solved. I would
> also think of priting LAPIC and IOAPIC entries to see how timer interrupt
> routing changes from first kernel to second.
I recently read the ioapic section in the opteron processor guide and noted the
ioapic routing field in the config registers, so I'll be looking at that.  We
also not that in the failing case on the systems in question the boot cpu is
_not_ the cpu that boots the kdump kernel, and its APIC ID is 1 not 0, IIRC


> Thanks
> Vivek

 *Neil Horman
 *Software Engineer
 *Red Hat, Inc.
 *nhorman at redhat.com
 *gpg keyid: 1024D / 0x92A74FA1

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