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From: "Robert N. M. Watson" <rwatson@FreeBSD.org>
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To: Andriy Gapon <avg@freebsd.org>
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Subject: Re: [poll / rfc] kdb_stop_cpus
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On 4 Jun 2011, at 09:22, Andriy Gapon wrote:

> on 03/06/2011 20:57 Robert N. M. Watson said the following:
>>=20
>> On 3 Jun 2011, at 16:13, Andriy Gapon wrote:
>>=20
>>> I wonder if anybody uses kdb_stop_cpus with non-default value. If, =
yes, I
>>> am very interested to learn about your usecase for it.
>>=20
>> The issue that prompted the sysctl was non-NMI IPIs being used to =
enter the
>> debugger or reboot following a core hanging with interrupts disabled. =
With
>> the switch to NMI IPIs in some of those circumstances, life is better =
-- at
>> least, on hardware that supports non-maskable IPIs. I seem to recall =
sparc64
>> doesn't, however?
>=20
> Seems to be so as Nathan has also pointed out for PPC.
> For this I also plan the following change:
>=20
> commit 458ebd9aca7e91fc6e0825c727c7220ab9f61016
>=20
>    generic_stop_cpus: move timeout detection code from under =
DIAGNOSTIC
>=20
>    ... and also increase it a bit.
>    IMO it's better to detect and report the (rather serious) condition =
and
>    allow a system to proceed somehow rather than be stuck in an =
endless
>    loop.

Agreed on detecting and reporting. It would be good to confirm that it =
works in practice, however, and also that there are no false positives. =
I'm not sure what the best test scenarios are for that.

Robert