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Date:      Fri, 16 Nov 2012 09:19:32 +0200
From:      Andriy Gapon <avg@FreeBSD.org>
To:        attilio@FreeBSD.org
Cc:        Ian Lepore <freebsd@damnhippie.dyndns.org>, Adrian Chadd <adrian@FreeBSD.org>, freebsd-arch@FreeBSD.org, freebsd-hackers@FreeBSD.org
Subject:   Re: [RFQ] make witness panic an option
Message-ID:  <50A5E904.9040808@FreeBSD.org>
In-Reply-To: <CAJ-FndCEMqbyQoNs0tmFBCBJHVJiA7arivAH_Og6vLEAxCt-TQ@mail.gmail.com>
References:  <CAJ-Vmo=i=Amo_QqHi4GnGie0Gc0YnK3XaRKjvBO-=SFboFYPmA@mail.gmail.com> <1353001175.1217.153.camel@revolution.hippie.lan> <CAJ-FndBP5Pi=SCpyBLK3b=HM_gQ9u8M4%2B1tLk9tA5X-gqismVA@mail.gmail.com> <1353009310.1217.172.camel@revolution.hippie.lan> <CAJ-Vmo=S3a1pyLHOe%2BSayVNDe=mAogQnkNpnSTakpOm56EdOUQ@mail.gmail.com> <50A555BD.1010105@FreeBSD.org> <CAJ-FndCEMqbyQoNs0tmFBCBJHVJiA7arivAH_Og6vLEAxCt-TQ@mail.gmail.com>

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on 16/11/2012 01:38 Attilio Rao said the following:
> On Thu, Nov 15, 2012 at 8:51 PM, Andriy Gapon <avg@freebsd.org> 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.
> 
> Please note that the "supposedly correct lock order", as for the
> definition that it is correct, can be used in several different
> stacks. I don't see the point of saving it somewhere.
> The only helpful case would be if the "wrong order" is catched first.
> If this is really the case, I suggest you to force the order you
> expect in the static table so that the first time the wrong order
> happens it yells.

Exactly my point - if I am a user of some code, not its developer, and I don't
know which one is the correct order I would have had the complete information
from the very start instead of having to jump through the hoops.

-- 
Andriy Gapon



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