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To: Andriy Gapon <avg@FreeBSD.org>
Subject: Re: [RFQ] make witness panic an option
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Cc: attilio@FreeBSD.org, Ian Lepore <freebsd@damnhippie.dyndns.org>,
 Adrian Chadd <adrian@FreeBSD.org>, freebsd-hackers@FreeBSD.org,
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On 11/15/12 12:51 PM, Andriy Gapon wrote:
> on 15/11/2012 22:00 Adrian Chadd said the following:
>> But I think my change is invaluable for development, where you want to
>> improve and debug the locking and lock interactions of a subsystem.
> My practical experience was that if you mess up one lock in one place, then it
> is a total mess further on.  but apparently you've got a different practical
> experience :-)
>
> What would indeed be invaluable to _me_ - if the LOR messages also produced the
> stack(s) where a supposedly correct lock order was learned.
>
Adrian is right.

In a large scale environment breakages will be introduced in places you 
do not have access to.

We need to enable developers to skip these areas and test their own code.

Without Adrian's concept then it forces someone who may have no idea 
about a subsystem to either be blocked, or to have to put his work aside 
to work on a problem that is someone else's responsibility.

I locked down SMP at a large company in a FreeBSD code base and had this 
same problem.  Adrian's patch would have helped all of us tremendously.

Adrian, can you look at my suggestion to merge with witness_kdb and see 
if that will suffice?

-Alfred