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Subject: Re: freebsd-head: suddenly NMI panics lead to ddb being unable to
 stop CPUs?
To: Julian Elischer <julian@freebsd.org>, Adrian Chadd <adrian@freebsd.org>
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Cc: freebsd-current <freebsd-current@freebsd.org>
From: Eric van Gyzen <eric@vangyzen.net>
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Date: Fri, 21 Aug 2015 10:54:33 -0500
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On 08/21/2015 10:30, Julian Elischer wrote:
> On 8/21/15 11:25 PM, Adrian Chadd wrote:
>> Ah, cool. I'll give it a whirl.
>>
>> I'm a little worried about having all of the other cores spinning in
>> this case (mostly thermal; the machines get VERY LOUD when the CPUs
>> are spinning..)
>>
> make each spin with the pause instruction.. and for N seconds (N being the CPU ID) or something

The patch (at the link below) does use the pause instruction.  The CPU has to spin as long as any CPU is in the debugger.

>> On 21 August 2015 at 08:19, Eric van Gyzen <vangyzen@freebsd.org> wrote:
>>> I mentioned this to Adrian, but I'll mention here for everyone else's benefit.
>>>
>>> Ryan is exactly right.  There was a thread a while ago, with a proposed patch from Kostik:
>>>
>>> https://lists.freebsd.org/pipermail/freebsd-arch/2014-July/015584.html
>>>