Re: [PATCH v2] x86/mce: Don't participate in rendezvous process once nmi_shootdown_cpus() was made

From: Xunlei Pang
Date: Mon Feb 20 2017 - 20:26:10 EST

On 02/21/2017 at 04:26 AM, Borislav Petkov wrote:
> On Mon, Feb 20, 2017 at 09:29:24PM +0800, Xunlei Pang wrote:
>> There is a small window between crash and kdump kernel boot, so
>> if a SRAO comes within this window it will also cause the mce
>> synchronization problem on the crashing cpu if we don't bail out the
>> crashing cpu.
> You mean, in the window between, kdump kernel starts writing out memory
> and the second, kexec-ed kernel?

Not kdump kernel starts dumping, just during nmi_shootdown_cpus(), if some
MCE comes after crashing_cpu was set and we don't skip crashing_cpu, then
the crashing cpu will enter mce handler and trigger the synchronization issue.

> If so, please add that information to the place in do_machine_check()
> where we check crashing_cpu so that we know why we're doing this
> temporary ignore of #MC.

Ok, will add, thanks for the feedback.