Timer interrupt lost on some x86_64 systems

Neil Horman nhorman at redhat.com
Wed Nov 7 09:00:06 EST 2007

Hey all-
	I've been getting reports of some x86_64 systems that, on kdump kernel
boot get stuck in calibrate_delay(),  in both RHEL kernels and upstream kernels.
The current thinking is that the lapic timer interrupt is no longer getting
delivered, likely because we handle a crash condition on a cpu that isn't the
boot cpu.  One known offender is this motherboard:
My current thought is that the TIMER_LVT entry is masked on all but the boot cpu
on this system (which is strange, as I was under the impression that the timer
interrupt was supposed to be enabled on all CPU's nominally.  At any rate, I was
going to try to read/write the TIMER_LVT on the crashing processor before we
jump to purgatory, or in purgatory itself, to see if that fixes the problem, but
I wanted to report the issue here to see if anyone had any alternate thoughts.
I know that intel ioapics had a timer related problem recently that caused the
same issue, but the fix doesn't seem to help in this case.

Thanks & Regards

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

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