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Date:      Sun, 25 Nov 2012 15:06:21 +0100
From:      Pawel Jakub Dawidek <pjd@FreeBSD.org>
To:        Attilio Rao <attilio@freebsd.org>
Cc:        "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, Giovanni Trematerra <giovanni.trematerra@gmail.com>, freebsd-arch@freebsd.org
Subject:   Re: [RFQ] make witness panic an option
Message-ID:  <20121125140620.GL1460@garage.freebsd.pl>
In-Reply-To: <CAJ-FndDxTf3pEQ5S5TyJTh3rDSnErcsvZzGwyWwChD_d81uVoQ@mail.gmail.com>
References:  <CAJ-Vmo=i=Amo_QqHi4GnGie0Gc0YnK3XaRKjvBO-=SFboFYPmA@mail.gmail.com> <CACfq090EiEiG7Ou2ZMUafWN6GLT9RNK1Q4tiOHnOBWe8GYJDjA@mail.gmail.com> <CAJ-VmonE3myRyeZ%2BAe0ZOXf7wKvC44rRVkFfDaEwnk8C-=5uoA@mail.gmail.com> <CAJ-FndCZPand_rx_uXUeetGMUZu1syGwjdFS7jv9BwdzuXvXOA@mail.gmail.com> <20121125123920.GI1460@garage.freebsd.pl> <CAJ-FndCnfqG4b_StS26WcPT-RhAhvJOOVryJ7rhi__y8Xkr92g@mail.gmail.com> <20121125131252.GJ1460@garage.freebsd.pl> <CAJ-FndAfCYmV7UawgxeKUMRaWaj%2B4XzVEUrxXnCC73sstJUqqg@mail.gmail.com> <20121125134743.GK1460@garage.freebsd.pl> <CAJ-FndDxTf3pEQ5S5TyJTh3rDSnErcsvZzGwyWwChD_d81uVoQ@mail.gmail.com>

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On Sun, Nov 25, 2012 at 01:48:23PM +0000, Attilio Rao wrote:
> On Sun, Nov 25, 2012 at 1:47 PM, Pawel Jakub Dawidek <pjd@freebsd.org> wr=
ote:
> > On Sun, Nov 25, 2012 at 01:37:19PM +0000, Attilio Rao wrote:
> >> On Sun, Nov 25, 2012 at 1:12 PM, Pawel Jakub Dawidek <pjd@freebsd.org>=
 wrote:
> >> > On Sun, Nov 25, 2012 at 12:42:16PM +0000, Attilio Rao wrote:
> >> >> On Sun, Nov 25, 2012 at 12:39 PM, Pawel Jakub Dawidek <pjd@freebsd.=
org> wrote:
> >> >> > WITNESS is a development tool. We don't ship production kernels w=
ith
> >> >> > WITNESS even compiled in. What is more efficient use of developer=
 time:
> >> >> > going through full reboot cycle every time or reading the warning=
 from
> >> >> > console, unloading a module, fixing the bug and loading it again?
> >> >> >
> >> >> > And if this option is turned off by default what is the problem?
> >> >>
> >> >> Yes, so, why do you write here?
> >> >
> >> > I'm trying to understand why do you object. Until now the only conce=
rn
> >> > you have that I found is that you are afraid of it being abused. I d=
on't
> >> > see how this can be abused if it is turned off by default. If someone
> >> > will commit a change that will turn it on by default, believe me, I'=
ll
> >> > unleash hell personally.
> >>
> >> So I don't understand what are you proposing.
> >> You are not proposing to switch BLESSING on and you are not proposing
> >> to import Adrian's patches in, if I get it correctly. I don't
> >> understand then.
> >
> > I propose to get Adrian's patches in, just leave current behaviour as
> > the default.
>=20
> So if I tell that I'm afraid this mechanism will be abused (and
> believe me, I really wanted to trimm out BLESSING stuff also for the
> same reason) and you say "you can't see how" there is not much we can
> discuss.

This is not what I said. I would see it as abuse if someone will
suddenly decided to turn off locking assertions by default in FreeBSD
base.

If he will turn that off on his private machine be it to speed up his
development (a good thing) or to shut up important lock assertion (a bad
thing) this is entirely his decision. He can already do that having all
the source code, its just more complex. Make tools, not policies.

BLESSING is totally different subject. You were afraid that people will
start to silence LORs they don't understand by committing blessed pairs
to FreeBSD base. And this situation is abuse and I fully agree, but I
also still think BLESSING is useful, although I recognize it might be
hard to prevent mentioned abuse.

In case of Adrian's patch nothing will change in how we enforce locking
assertions in FreeBSD base.

> You know how I think, there is no need to wait for me to reconsider,
> because I don't believe this will happen with arguments like "I don't
> think", "I don't agree", etc.

I provide valid arguments with I hope proper explanation, you choose not
to address them or ignore them and I hope this will change:)

--=20
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl

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